{"id":163,"date":"2024-04-05T11:04:04","date_gmt":"2024-04-05T11:04:04","guid":{"rendered":"https:\/\/paradoxa.me\/?p=163"},"modified":"2024-04-17T16:43:02","modified_gmt":"2024-04-17T16:43:02","slug":"py4e-python-course-by-dr-chuck","status":"publish","type":"post","link":"https:\/\/paradoxa.me\/index.php\/2024\/04\/05\/py4e-python-course-by-dr-chuck\/","title":{"rendered":"~ PY4E (Python Course by Dr.Chuck)"},"content":{"rendered":"

PY4E – Python For Everybody<\/h1>\n

Learning Python with Dr.Chuck free course<\/h2>\n

First of all I would like to thank D. Chuck for sharing his knowledge by creating this free online course<\/h3>\n
NOTE: The following are just my study note.\r\n\r\n<\/pre>\n
#1 – Why use a Programming language<\/h2>\n
Programmer write a sequence of instructions or code to solve problems.
\n<\/span>Computers takes typing literally so they will do not accept or recognize errors.<\/span><\/p>\n
~ What the Hardware does:<\/span><\/h3>\n
– CPU ask for instruction
\n<\/span>– MEMORY RAM store the instructions (faster temporary storage)
\n<\/span>– SECONDARY MEMORY (HDD\u2019s or SSD\u2019s) Store the instruction (slow permanent storage)
\n<\/span>– MOTHERBOARD connects all the components<\/span><\/p>\n
~ What the Language Software does : <\/span><\/h3>\n
– You write a file\/program
\n<\/span>– It get loaded into RAM
\n<\/span>– Python will translate the language so the CPU understand it
\n<\/span>– Once the program is terminated the python will translate back to you the answer<\/span><\/p>\n
~ Python (ATOM text editor to write Python is recommended in the course)<\/span><\/h3>\n
You can run python inside the terminal, but generally you will type the script on a text editor and run it after you save the file with a .py extension.
\nIf you type a mistake python will display a \u201csyntax error\u201d message to let you know where the mistake was made.<\/span><\/p>\n
~ Elements of python: <\/span><\/h3>\n
– Vocabulary\/words : reserved and variables
\n<\/span>– Sentence structure : valid syntax patterns
\n<\/span>– Story structure : construct a purposeful program<\/span><\/p>\n
~ Vocabulary Reserved Words (you can\u2019t use the following for other purposes): <\/span><\/h3>\n
False \u2013 class \u2013 return \u2013 is \u2013 finally \u2013 None \u2013 if \u2013 for \u2013 lambda \u2013 continue \u2013 True \u2013 def \u2013 from \u2013 while \u2013 nonlocal \u2013 and \u2013 del \u2013 global \u2013 not \u2013 with \u2013 as \u2013 elif \u2013 try \u2013 or \u2013 yield \u2013 assert \u2013 else \u2013 import \u2013 pass \u2013 break \u2013 except \u2013 in \u2013 raise.<\/em> <\/span><\/p>\n
~ Sentences or Lines:<\/span><\/h3>\n
Example: (#<\/strong> value means is a comment and python skips what\u2019s after)
\n<\/span>x = 2\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\u00a0 \u00a0 #assignment statement
\n<\/span>x = x + 2\u00a0\u00a0\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 #assignment with expression
\n<\/span><\/em>print(x)\u00a0\u00a0\u00a0\u00a0\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 #print statement<\/em> <\/span><\/p>\n
~ Structure: <\/span><\/h3>\n
The script can be in a sequence (step after step), conditional (If <\/strong>followed variables), repeated or just few lines can be repeated over and over.
\nA program can combine different lines together.<\/span><\/p>\n
 <\/p>\n
#2 – Variables, Expression and Statement<\/h2>\n
~ Constants:<\/span><\/h3>\n
constant are numbers, letters and strings (string use single quote (\u2018) or double quote (\u201c))<\/span><\/p>\n
~ Variables:<\/span><\/h3>\n
Basically you ask python to save specific digit for determinate variables.
\n<\/span>Examples: <\/span>x = 2<\/em> , but remember that if after you follow up with x = 5<\/em> it will overwrite the new value over the old one.
\n<\/span><\/p>\n
Variables must start with letter or _ and can be written with letter, underscores and numbers (case sensitive)
\n<\/span>– Accepted Examples:\u00a0 variables\u00a0\u00a0 variables21\u00a0\u00a0 _variables<\/em>
\n– <\/span>Unaccepted Examples:\u00a0\u00a0 21variables \u00a0 @variables\u00a0\u00a0 varia.bles<\/em>
\n– <\/span>Accepted but preferably to avoid:\u00a0 vArIaBlElS \u00a0 Variables\u00a0\u00a0 VARIABLES<\/em><\/span><\/p>\n
But is good practice to use Mnemonic Variables Names (mnemonic = memory aid), so they are more understandable to everybody as variable.
\nInstead, for example, of using \u201cx\u201d we can use \u201c_hours\u201d if we refer to hours.<\/span><\/p>\n
~ Sentences or Lines<\/span><\/h3>\n
Assignment statement:
\n<\/span>we use = to assign variables x = 2<\/em> or x = 2 + x * 3 \/ 4<\/em>
\nthey can be numeric expression made with: (), % (remainder) ** (power of), * \/, + – . In order of importance, and if they are the same level it goes from left to right.<\/span><\/p>\n
~ Type<\/span><\/strong><\/p>\n
Python recognize difference between numbers and string. But it can no compute an operation with string and number (trackback\/type error).
\nBy writing type<\/b>, python will describe which type the constant is: \u2018int\u2019=1 \u2018float\u2019=1.0 \u2018str\u2019=one .<\/span><\/p>\n
But you can convert for example:
\nfloat(1) \/ 1 = 1.0 \/ 1 = 1.0<\/em><\/span><\/p>\n
You can convert when possible<\/em> with int() or float() like the example above.<\/span><\/p>\n
~ Input<\/span><\/strong><\/p>\n
when we type input()<\/b>, python will stop as is asking the user a question (that will return as a string) and after the user answer it will complete the code.
\nExample:
\n_name = input(\u2018who are you? \u2019)\u00a0\u00a0 \u00a0 \u00a0\u00a0 #here user will digit their name and press enter<\/em>
\n<\/span>print(\u2018Welcome\u2019, _name)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \u00a0 \u00a0\u00a0 #It will print: Welcome , Username<\/em>
\n<\/span><\/p>\n
 <\/p>\n
#3 – Conditional Execution<\/h2>\n
~ Conditional statement<\/span><\/h3>\n
We use if<\/strong> to create a condition follow by the following simbols: <<\/strong> (less than), <=<\/strong> (less or equal), ==<\/strong> (equal), >=<\/strong> (greater or equal), ><\/strong> (greater) and !=<\/strong> (not equal)
\n<\/span>Example:
\n~x = 5<\/em>
\n~if x < 10:<\/em>
\n<\/span>~\u00a0\u00a0\u00a0 print(\u2018Smaller\u2019)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 # The space in front is an indent
\n<\/span>~if x > 20:
\n~\u00a0\u00a0\u00a0 print(\u2018Bigger\u2019)
\n<\/span>~print(\u2018Finito\u2019)<\/span><\/em><\/p>\n
~ Block and indentations (4 spaces or 1 tab in atom text)<\/span><\/h3>\n
A block is a set of lines maintained with indentations after if<\/b> or for<\/b>.
\nThe indentation is composed by 4 spaces but in some software as Atom you can type the Tab, It’s important that the indentation has the same length to be part of the same block.
\n<\/span><\/p>\n
One indentation:<\/span><\/h4>\n
~x = 5
\n~if > 1
\n<\/span>~\u00a0\u00a0\u00a0 print (\u2018bigger than one\u2019)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #increase indentation
\n<\/span>~\u00a0\u00a0\u00a0 print (\u2018still bigger\u2019)
\n<\/span>~print (\u2018done with 2\u2019)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #decrease indentation<\/span><\/em><\/p>\n
Double indentation or nested decision<\/span><\/h4>\n
~x = 5
\n~if > 1
\n<\/span>~\u00a0\u00a0\u00a0 print (\u2018bigger than one\u2019)
\n<\/span>~\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 print (\u2018still bigger\u2019)
\n~\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 # empty line are not considered by python
\n~print (\u2018finito\u2019)<\/span><\/em><\/p>\n
Two-way decision
\n<\/span><\/h4>\n
To use a two-way decision you need to use else <\/strong>, which also close the code : this one or that one
\n~x = 4
\n~if x > 2 :
\n~\u00a0\u00a0\u00a0 print(\u2018Bigger\u2019)
\n~else :
\n<\/span>~\u00a0\u00a0\u00a0 print(\u2018Smaller\u2019)
\n~
\n~<\/span><\/em>print(\u2018finito\u2019)<\/span><\/em><\/p>\n
Multi-way decision
\n<\/span><\/h4>\n
They also called puzzle and are made with elif <\/strong>, you can have multiple elif but be sure that one condition don’t match the following condition
\n~x = 4
\n<\/span>~if x < 2 :
\n~\u00a0\u00a0\u00a0 print(\u2018small\u2019)
\n<\/span>~elif x < 10 :
\n<\/span>~\u00a0\u00a0\u00a0 print(\u2018medium\u2019)
\n<\/span>~else :
\n<\/span>~\u00a0\u00a0\u00a0 print(\u2018large\u2019)
\n~
\n~<\/span><\/em>print(\u2018finito\u2019)<\/span><\/em><\/p>\n
Try \/ Except structure<\/span><\/h4>\n
It surrounds a dangerous section of code (only one line recommended) so if for some reason blows, python will still run the comand till the end.
\n<\/span>~astr = \u2018hello bob\u2019
\n~try:
\n<\/span>~\u00a0\u00a0\u00a0 istr = int (astr) \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 #you can\u2019t convert letters in numbers so the code blows up
\n<\/span>~except:
\n<\/span>~\u00a0\u00a0\u00a0 istr = -1\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #but it will use -1 instead
\n<\/span>~print (\u2018First\u2019, istr)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 # so the code will print : First -1<\/span><\/em><\/p>\n

\n~astr = \u2018123\u2019
\n~try:
\n<\/span>~\u00a0\u00a0\u00a0 istr = int (astr)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #you can convert letters in numbers so the code will print
\n<\/span>~except:
\n~\u00a0\u00a0\u00a0 istr = -1\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #no need to read this line now because the code worked
\n<\/span>~print (\u2018Second\u2019, istr)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #and will print : Second 123<\/span><\/em><\/p>\n
 <\/p>\n
#4 – Function<\/h2>\n
Only write function if they actually required, for 20 lines of code they are probably not necessary<\/span><\/p>\n
~ def<\/h3>\n
Def function = define code
\nIt defines a set reusable code to avoid typing it over and over inside the file<\/span><\/p>\n
~def ciao
\n<\/span>~\u00a0\u00a0\u00a0 print(\u2018hello\u2019)
\n~ciao()\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #hello
\n~print(\u2018how are you\u2019)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #how are you
\n~ciao()\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #hello<\/span><\/em><\/p>\n
~def greet(lang) :
\n<\/span>~\u00a0\u00a0\u00a0 if lang == \u2018es\u2019\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #if the user type es it will print hola
\n<\/span>~\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 print(\u2018hola\u2019)
\n<\/span>~\u00a0\u00a0\u00a0 elif lang == \u2018fr\u2019\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #if the user type fr it will print bonjour
\n<\/span>~\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 print(\u2018bonjour\u2019)
\n<\/span>~\u00a0\u00a0\u00a0 else:\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #if the user type any other language it will ~\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 print hello
\n<\/span>~print(\u2018hello\u2019)<\/span><\/em><\/p>\n
~ Return value
\n<\/span><\/h3>\n
It used with the return <\/strong>instead of the print <\/strong>command:<\/p>\n
~def greet(lang) :
\n<\/span>~\u00a0\u00a0\u00a0 if lang == \u2018es\u2019\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #if the user type es it will return hola
\n<\/span>~\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 return \u2018hola\u2019
\n<\/span>~\u00a0\u00a0\u00a0 elif lang == \u2018fr\u2019\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #if the user type fr it will return bonjour
\n<\/span>~\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 return \u2018bonjour\u2019
\n<\/span>~\u00a0\u00a0\u00a0 else:\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #if the user type any other language it will ~\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 return hello
\n<\/span>~return \u2018hello\u2019<\/span><\/em><\/p>\n
~ Max function<\/span><\/h3>\n
Python assign a value of the letters and pick up the higher value ones with the max <\/strong>function
\n<\/span><\/p>\n
~big = max(\u2018hello world\u2019)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 # \u2018hello world\u2019 is an argument
\n<\/span>~print(big)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 # it will print w<\/span><\/em><\/p>\n
 <\/p>\n
#5 – Loops & Iterations<\/h2>\n
~ while<\/h3>\n
While is similar to the if<\/strong> statement but it will run till becomes False<\/strong>,
\nIt’s called also iteration variable and indefinite loop.
\nAvoid to create infinite iteration as the computer will keep spinning, on the other and,
\nZero Trip loop are loops that don\u2019t run.<\/span><\/p>\n
~n = 5
\n<\/span>~while n > 0 :\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #it will keep running the question till is n=0
\n~\u00a0\u00a0\u00a0 print(n)
\n~\u00a0\u00a0\u00a0 n = n \u2013 1
\n~print(\u2018finito\u2019)<\/span><\/em><\/p>\n
~ break<\/h3>\n
break will break the loop once the user put the selected input
\n<\/span><\/p>\n
~while True :
\n<\/span>~\u00a0 \u00a0 line = (\u2018> \u2019)
\n<\/span>~ \u00a0\u00a0 if line == \u2018done\u2019 :
\n<\/span>~\u00a0 \u00a0\u00a0\u00a0\u00a0\u00a0 break \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 #loops breaks when user types done
\n<\/span>~\u00a0\u00a0\u00a0 print(line)
\n<\/span>~print (\u2018finito\u2019)<\/span><\/em><\/p>\n
~ continue<\/h3>\n
continue will skip everything after and go back to the specified line<\/span><\/p>\n
~while True:
\n~ \u00a0\u00a0 line = (\u2018> \u2019)
\n<\/span>~\u00a0\u00a0\u00a0 if line[0] == \u2018#\u2019 :
\n<\/span>~ \u00a0 \u00a0 \u00a0\u00a0 continue \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\u00a0 #when user types # it will go back to line0
\n~\u00a0\u00a0\u00a0 if line == \u2018done\u2019 :
\n<\/span>~\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 break
\n<\/span><\/em>~\u00a0\u00a0\u00a0 print(line)<\/em>
\n~print (\u2018finito\u2019)<\/em>
\n<\/span><\/p>\n
~ for<\/h3>\n
for is used to set definite loops, imagine the code being a contract with python where it has to run once the list of items<\/span><\/p>\n
~for y in [5, 4, 2, 3,1]
\n<\/span>~\u00a0\u00a0\u00a0 print(y)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #it will print once each 5,4,2,3,1
\n~print(\u2018finito\u2019)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #once completed will print finito
\n<\/span><\/em><\/p>\n
~x = [\u2018afternoon\u2019, \u2018bye\u2019, \u2018morning\u2019]
\n~for y in x :
\n<\/span>~ \u00a0\u00a0 print(\u2018good\u2019 , y)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #print good afternoon, good bye, good morning
\n<\/span>~print(\u2018finito\u2019)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #when finish the loop finito<\/span><\/em><\/p>\n
~ Largest Number<\/h3>\n
Largest number can be found by assigning one variable ><\/em> the other<\/span><\/p>\n
~largest = -1
\n~print (\u2018inizio\u2019, largest)
\n<\/span>~for xyz in [5, 9, 2, 8, 10, 3, 4] :
\n<\/span>~\u00a0\u00a0\u00a0 if xyz > largest :
\n<\/span>~\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 largest = xyz\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #replace -1 with 5, 9, 10 in order. Skips lower numbers
\n<\/span>~\u00a0\u00a0\u00a0 print(largest, xyz)
\n<\/span>~print(\u2018fine\u2019, largest) \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 #fine, 10<\/span><\/em><\/p>\n
~ Counting using loops<\/h3>\n
~ripetizioni = 0
\n<\/span>~somma = 0
\n<\/span>~print(\u2018inizio\u2019, ripetizioni, somma)
\n<\/span>~for numeri in [9, 41, 12, 3, 74, 15] :
\n<\/span>~ \u00a0\u00a0 ripetizioni = ripetizioni + 1\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #how many loops
\n<\/span>~\u00a0\u00a0\u00a0 somma = somma + numeri\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #total sum
\n<\/span>~\u00a0\u00a0\u00a0 print(ripetizioni, somma, numeri)
\n<\/span><\/em>~print(\u2018Dopo\u2019, ripetizioni, somma, somma \/ ripetizioni) \u00a0 \u00a0 #show count, sum and average value<\/em> <\/span><\/p>\n
~ Filter using if<\/h3>\n
~print(\u2018Prima\u2019)
\n<\/span>~for valore in [9, 41, 12, 3, 74, 15] :
\n<\/span>~ \u00a0\u00a0 if valore > 20:
\n<\/span>~\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 print(\u2018Large number\u2019, valore)
\n<\/span>~print(\u2018Dopo\u2019)<\/span><\/em><\/p>\n
~ Boolean Variable<\/h3>\n
Variable that return only values of True or False<\/span><\/p>\n
~cerca = False
\n~print(\u2018Prima\u2019, cerca)
\n<\/span>~for valore in [4, 756, 2, 78] :
\n~ \u00a0\u00a0 if valore == 2 :
\n<\/span>~\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 cerca = True \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 #when value 2 is found, become True
\n~\u00a0\u00a0\u00a0 print(cerca, valore)
\n<\/span>~print(\u2018Dopo\u2019, cerca)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 # print True<\/span><\/em><\/p>\n
~ for & is None<\/h3>\n
We can create a better way to find values (largest or smallest) by introducing is<\/strong> followed by None<\/strong>.
\nThe is<\/strong> operator (or is not<\/strong>) is stronger than ==<\/strong> because the value has to be exactly the same (by number and type).
\nNone<\/strong> is a constant and means emptiness.<\/span><\/p>\n
~piccolo = None
\n~for valore in [3, 2, 6, 8, 1] :
\n~ if piccolo is None :\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #no initial value is consider
\n<\/span>~ piccolo = valore \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 #start with the first value in the list
\n<\/span>~ elif valore < piccolo :
\n~ piccolo = valore\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #replace the value with the smallest
\n~ print piccolo, valore
\n~
\n<\/span>~print(\u2018dopo\u2019, piccolo)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #dopo, 1<\/span><\/em><\/p>\n
 <\/p>\n
#6 – Strings<\/h2>\n
A string is a sequence of characters written between \u2018 \u2019<\/strong> or \u201c \u201d<\/strong>.
\nEven if contains numbers, is still consider a string; although we can convert numbers in a string with int()<\/strong>.
\nWe can use the +<\/strong> symbols to concatenate multiple strings.
\nBecause it gives us more control we tend to read data in strings and then convert if necessary.
\nWe can also index the strings by using the [ ]<\/strong> starting with 0,1,2…:<\/span><\/p>\n
~nazione = \u2018united kingdom\u2019
\n~lettera = nazione[0]\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #the 0 number means the first letter
\n<\/span>~print(letter)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #In this case will be u (if we put 4 it will be t)<\/span><\/em><\/p>\n
~x = 3<\/em>
\n~y = [x \u2013 1]\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #we CAN\u2019T index beyond the length of the string
\n<\/span>~print(y)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #i<\/span><\/em><\/p>\n
~ len<\/h3>\n
len<\/strong> measure the length of the string<\/span><\/p>\n
~nazione = \u2018united kingdom\u2019
\n~x = len(nazione)
\n<\/span>~print(x)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #14<\/span><\/em><\/p>\n
~ Creating loops to display the string<\/h3>\n
~nazione = \u2018united kingdom\u2019
\n<\/span>~indice = 0
\n~while indice < len(nazione) :
\n<\/span>~\u00a0\u00a0\u00a0 lettera = nazione[indice]
\n<\/span>~\u00a0\u00a0\u00a0 print(indice, lettera)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #0u
\n<\/span>~\u00a0\u00a0\u00a0 indice = indice + 1\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #looping back inside the index: 1n, 2i, 3t\u2026<\/span><\/em><\/p>\n
~nazione = \u2018united kingdom\u2019
\n~for lettera in nazione:
\n<\/span>~\u00a0\u00a0\u00a0 print(lettera)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #same result as above but in an simpler and elegant way<\/span><\/em><\/p>\n
obviously we can loop and count as in the previous chapter too<\/span><\/p>\n
~ Extrapolate from the string<\/h3>\n
To extrapolate part of the string use [x : y]<\/strong>\u00a0 which means from, to (but not including the last digit)<\/span><\/p>\n
~nazione = \u2018united kingdom\u2019
\n<\/span>~print(nazione[0:4])\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \u00a0 \u00a0 \u00a0 \u00a0\u00a0 \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #unit (not include the 4th<\/sup> )
\n<\/span>~print(nazione[7:50])\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\u00a0 \u00a0 #kingdom (you can do it even if exceed)
\n~print(nazione[:6])\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #united (you can leave blank first and last)<\/span><\/em><\/p>\n
~ Concatenation<\/h3>\n
~x = good
\n<\/span>~y = x + \u2018morning\u2019
\n~print(y)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #goodmorning (without space)
\n<\/span>~z = x + \u2018 \u2019 + \u2018morning\u2019
\n<\/span>~print(z)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #good morning (with space)<\/span><\/em><\/p>\n
~ in<\/h3>\n
~x = \u2018united kingdom\u2019
\n<\/span>~\u2018nit\u2019 in x\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #True
\n<\/span>~\u2018b\u2019 in x\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #False<\/span><\/em><\/p>\n
~ .lower & .upper<\/h3>\n
~x = Ciao
\n~y = x.lower()
\n<\/span>~print(y) \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\u00a0 #ciao (all lower case)
\n~z = x.upper
\n~print(z)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #CIAO<\/span><\/em><\/p>\n
~ .find<\/h3>\n
~x = Ciao
\n~y = x.find(\u2018a\u2019)
\n~print(y)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #2 (index position)
\n~z = x.find(\u2018m\u2019)
\n<\/span>~print(z)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #-1 (no character found)<\/span><\/em><\/p>\n
~ .replace<\/h3>\n
~x = buon giorno
\n~y = x.replace(\u2018giorno\u2019 , \u2018pomeriggio\u2019)
\n~print(y)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #buon pomeriggio
\n~z = x.replace(\u2018g\u2019 , \u2018KK\u2019)
\n<\/span>~print(z)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #buon pomeriKKio<\/span><\/em><\/p>\n
~ Stripping withspaces<\/h3>\n
Whitespaces are referred to spaces \u2018 \u2019, tab \u2018\u00a0\u00a0\u00a0 \u2019 and all the blanks.<\/span><\/p>\n
~x = \u2018 \u00a0\u00a0 ciao \u00a0\u00a0 \u2019
\n~x.lstrip()
\n<\/span>~print(x)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #\u2018ciao \u00a0\u00a0 \u2019
\n~x.rstrip()
\n~print(x)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #\u2018 \u00a0\u00a0 ciao\u2019
\n~x.strip()
\n~print(x)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #\u2018ciao\u2019<\/span><\/em><\/p>\n
~ Prefixes<\/h3>\n
Basically asks does the string starts with …?<\/span><\/p>\n
~x = \u2018ciao come stai?\u2019
\n~x.startwith(\u2018ciao\u2019)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #True (is case sensitive)<\/span><\/em><\/p>\n
~ Strings variables<\/h3>\n
Check the python documentation where\u00a0 it will explain in details at
\n( https:\/\/docs.python.org\/3\/library\/stdtypes.html#string-methods<\/a> ).
\nO<\/span>r to check which one is availible from python:<\/span><\/p>\n
~x = Ciao
\n~type(x)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #\u2018str\u2019 (classified that it is a string)
\n~dir(x) \u00a0 \u00a0 \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 # will shows all the variables<\/span><\/em><\/p>\n
 <\/p>\n
#7 – Files (secondary memory)<\/h2>\n
~ Text Files<\/h3>\n
Text file are considered a sequence of lines.
\nWe need to tell Python which file we want to use and what we will be doing with it.
\nFor this we use the open() <\/strong>function, that will return a “file handle” which is a variable use to perform operations on the file.
\n(same concept as File -> Open<\/em> in word).<\/p>\n
Example: ~fhandle = open(‘filename’, ‘mode’) . Where mode is optional and it will be ‘r’ <\/strong>(read) or ‘w’ <\/strong>(write). Filename on the other hand is considered as a string.<\/p>\n
~fhand = open(‘file.txt’, ‘r’)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #fhand is a wrapper<\/em>
\n~print(fhand)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #will show wrapper, name, mode, encoding<\/em><\/p>\n
If file doesen’t exist : traceback<\/p>\n
~ \\n<\/h3>\n
\\n<\/strong> means newline (where the line ends) and it’s considere only 1 characther<\/p>\n
~x = ‘y\\nz’\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #will print y (new line) z<\/em>
\n~len(x)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #3<\/em><\/p>\n
~ Reading file<\/h3>\n
~fhand = open(‘file.txt’)<\/em>
\n~for riga in fhand:<\/em>
\n~\u00a0\u00a0\u00a0 print(riga)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #read all the line in the file<\/em><\/p>\n
~fhand = open(‘file.txt’)
\n<\/em>~inp = fhand.read()<\/em>
\n~print(len(inp))\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #will show the number of character
\n~print (inp[:20]\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #will sho the first 20 character
\n<\/em><\/p>\n
~ Counting line<\/h3>\n
~fhand = open(‘file.txt’)
\n~conta = 0
\n<\/em>~for riga in fhand:
\n~\u00a0\u00a0\u00a0 conta = conta + 1<\/em>
\n~\u00a0\u00a0\u00a0 print(‘numero righe:’, conta)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #numero righe : 100
\n<\/em><\/p>\n
~ Searching<\/h3>\n
~fhand = open(‘file.txt’)
\n~for riga in fhand:
\n~\u00a0\u00a0\u00a0 line = line.rstrip()\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #to remove the \\n
\n~\u00a0\u00a0\u00a0 if riga.startwith(‘From:’) :
\n~\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 print(riga)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #will print all lines that start with from
\n<\/em><\/p>\n
or by using if not<\/p>\n
~fhand = open(‘file.txt’)
\n~for riga in fhand:
\n~\u00a0\u00a0\u00a0 line = line.rstrip()\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #to remove the \\n
\n~\u00a0\u00a0\u00a0 if not riga.startwith(‘From:’) :
\n~\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 continue
\n~\u00a0\u00a0\u00a0 print(riga)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #will print all lines that start with from<\/em><\/p>\n
or to run the same program to different file we can add the following line above using input:<\/p>\n
~fname = input(‘file.txt’)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #file.txt now is a variable<\/p>\n
~ Bad names file or if they don’t exist<\/h3>\n
If the file file.txt doesn’t exist we will have a TB error. to prevent:<\/p>\n
~fname = input(‘file.txt’)
\n~try:
\n~\u00a0\u00a0\u00a0 fhand = open(fname<\/em>)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #if file exist will go to the following block
\n~except:
\n~\u00a0\u00a0\u00a0 print(‘file cannot be opened:’, fname)
\n~\u00a0\u00a0\u00a0 quit()\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #if doesn’t will print file cann… and then quit
\n~
\n~conta = 0
\n~for riga in fhand:
\n~\u00a0\u00a0\u00a0 conta = conta + 1
\n~\u00a0\u00a0\u00a0 print(‘numero righe:’, conta)
\n<\/em><\/p>\n
 <\/p>\n
#8 – List []<\/h2>\n
List are basically collection of data. Programming can be divided in two, Algorithms (set of rules to solve problems) and Data Structures (organizing data).<\/p>\n
Python can run numbers, strings and Int as follows: x = [‘ciao’, 3, 4.5] #it always start from 0 (not 1)
\n<\/em>Even list of lists x = [5, [2, 3], 9] <\/em>and empty list []
\n<\/em><\/p>\n
Stirngs are Immutable but list are mutable<\/p>\n
~ in (works the same as in string)<\/h3>\n
~ len<\/h3>\n
~x = [1, 3, 5, ‘bob’]<\/em>
\n~print(len(x))\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #4<\/em><\/p>\n
~ range<\/h3>\n
~x = [1, 3, 5, ‘bob’, 5]<\/em>
\n~print (range(len(x)))\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #[0, 1, 2, 3, 4]<\/em><\/p>\n
~print(range(4))\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #[0, 1, 2, 3]<\/em><\/p>\n
can be use with for
\n~x = [1, 4, 5]<\/em>
\n~for y in x :<\/em>
\n~\u00a0\u00a0\u00a0 print(‘num:’, y)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #num: 1\u00a0\u00a0\u00a0 num: 4\u00a0\u00a0\u00a0 num: 5<\/em>
\n~<\/em>
\n~for z in range(len(x)) :<\/em>
\n~\u00a0\u00a0\u00a0 y = x[z]<\/em>
\n~\u00a0\u00a0\u00a0 print(‘num:’, y)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #num: 1\u00a0\u00a0\u00a0 num: 4\u00a0\u00a0\u00a0 num: 5 (same result)<\/em><\/p>\n
~ concatenating<\/h3>\n
~a = [2, 4, 6]<\/em>
\n~b = [3, 5,]<\/em>
\n~c = a + b<\/em>
\n~print(c)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0\u00a0 #[2, 4, 6, 3, 5]<\/em><\/p>\n
~ sliced<\/h3>\n
~a = [2, 4, 6]<\/em>
\n~a[:1]\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #[2, 4]<\/em><\/p>\n
# list methods<\/h3>\n
shows all the stuff we can do with the a list
\n~x = list<\/em>
\n~type(x)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #<type ‘list’> <\/em>
\n~dir(x)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #[‘append’, ‘count’, ‘extend’, ‘index’, ‘insert’, ‘pop’, ‘remove’, ‘reverse’, ‘sort’]<\/em><\/p>\n
~ append<\/h3>\n
~x = list()\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #to create an empty list (list<\/strong> is a reserved word) <\/em>
\n~x.append(‘1’)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #to insert 1 in the list<\/em><\/p>\n
~ sort<\/h3>\n
~x = [‘m’, ‘a’, ‘q’]<\/em>
\n~x.sort()
\n<\/em>~print(x)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #[‘a’, ‘m’, ‘q’]<\/em><\/p>\n
~ built-in function<\/h3>\n
~x = [1, 3, 5, 9, 2]
\n~print(len(x))\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #5
\n~print(max(x))\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #9
\n~print(min(x))\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #1
\n~print(sum(x))\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #21
\n~print(sum(x)\/len(x))\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #4.2
\n<\/em><\/p>\n
# check 4:06:05 to see some examples<\/pre>\n
~ Split<\/h3>\n
String and list are related to each other. the following example is a double split to extract the mail.<\/p>\n
~x = ‘da email@provider.com date’<\/em>
\n~y = x.split()\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #in this case it only consider whitespaces (does NOT count ,.:; etc…)<\/em>
\n~print(y)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #[‘da’, ’email@provider.com’, ‘date’] convert the original in different strings
\n~mail = y[1]\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #it refer to the string 1 in this case\u00a0 ’email@provider.com’
\n<\/em>~z = x.split(@)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 #in this case it split with e<\/em>
\n~print(z)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #[’email’, ‘ provider’] convert the original in different strings
\n~print(z[0])\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #it will print email
\n<\/em><\/p>\n
~ guardian pattern and how to fix the issues<\/h3>\n
Original code, it printed some but it TB at some point and we don’t know how:<\/p>\n
~abc = open(‘file.txt’)<\/em>
\n~<\/em>
\n~for riga in abc:<\/em>
\n~\u00a0\u00a0\u00a0 riga = riga.rstrip()<\/em>
\n~\u00a0\u00a0\u00a0 prl = riga.split()<\/em>
\n~\u00a0\u00a0\u00a0 if prl[0] != ‘da’ :<\/em>
\n~\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 continue<\/em>
\n~\u00a0\u00a0\u00a0 print(prl[2])<\/em><\/p>\n
To start finding the problem we need to insert print() <\/strong>till we find where it TB<\/p>\n
~abc = open(‘file.txt’)<\/em>
\n~<\/em>
\n~for riga in abc:<\/em>
\n~\u00a0\u00a0\u00a0 riga = riga.rstrip()<\/em>
\n~\u00a0\u00a0\u00a0 print(‘riga’, riga) \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #to check why<\/em><\/strong>
\n~\u00a0\u00a0\u00a0 prl = riga.split()<\/em>
\n~\u00a0\u00a0\u00a0 print(‘parola’, prl\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #to check why<\/em><\/strong>
\n~\u00a0\u00a0\u00a0 if prl[0] != ‘da’ :
\n~\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 print(‘ignore’)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #to check why<\/strong><\/em>
\n~\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 continue<\/em>
\n~\u00a0\u00a0\u00a0 print(prl[2])<\/em><\/p>\n
After running the program we discovered that in this case the problem was that some line didn’t have words on them.<\/p>\n
~abc = open(‘file.txt’)<\/em>
\n~<\/em>
\n~for riga in abc:<\/em>
\n~\u00a0\u00a0\u00a0 riga = riga.rstrip()<\/em>
\n~\u00a0\u00a0\u00a0 print(‘riga’, riga)<\/em>
\n~\u00a0\u00a0\u00a0 prl = riga.split()<\/em>
\n~\u00a0\u00a0\u00a0 print(‘parola’, prl
\n~\u00a0\u00a0\u00a0 # Guardian pattern<\/strong>
\n~\u00a0\u00a0\u00a0 if len(prl) < 1 :<\/strong>
\n~\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 continue\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #if the line has less the one word -> continue<\/strong><\/em>
\n~\u00a0\u00a0\u00a0 if prl[0] != ‘da’ :
\n~\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 print(‘ignore’)<\/em>
\n~\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 continue<\/em>
\n~\u00a0\u00a0\u00a0 print(prl[2])<\/em><\/p>\n
or another way like the following<\/p>\n
~abc = open(‘file.txt’)<\/em>
\n~<\/em>
\n~for riga in abc:<\/em>
\n~\u00a0\u00a0\u00a0 riga = riga.rstrip()<\/em>
\n~\u00a0\u00a0\u00a0 print(‘riga’, riga)
\n~\u00a0\u00a0\u00a0 if riga == ‘ ‘ :<\/strong>
\n~\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 continue\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #if the line is a blank skip the line<\/strong><\/em>
\n~\u00a0\u00a0\u00a0 prl = riga.split()<\/em>
\n~\u00a0\u00a0\u00a0 print(‘parola’, prl<\/em>
\n~\u00a0\u00a0\u00a0 if prl[0] != ‘da’ :
\n~\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 print(‘ignore’)<\/em>
\n~\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 continue<\/em>
\n~\u00a0\u00a0\u00a0 print(prl[2])<\/em><\/p>\n
coming back to the guardian line we can get ready of the extra, and make the guardian stronger, in this case if we try to print (in the last piece of code) a line with less than 2 words it will TB<\/p>\n
~abc = open(‘file.txt’)<\/em>
\n~<\/em>
\n~for riga in abc:<\/em>
\n~\u00a0\u00a0\u00a0 riga = riga.rstrip()<\/em>
\n~\u00a0\u00a0\u00a0 prl = riga.split()<\/em>
\n~\u00a0\u00a0\u00a0 # Guardian a little stronger<\/strong><\/em>
\n~\u00a0\u00a0\u00a0 if len(prl) < 3 :\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #by changing\u00a0 to 3 it will skip all the line will less than 3<\/em><\/strong>
\n~\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 continue<\/em><\/strong>
\n~\u00a0\u00a0\u00a0 if prl[0] != ‘da’ :<\/em>
\n~\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 continue<\/em>
\n~\u00a0\u00a0\u00a0 print(prl[2])<\/em><\/p>\n
or we can compound the guardian like this<\/p>\n
~abc = open(‘file.txt’)<\/em>
\n~<\/em>
\n~for riga in abc:<\/em>
\n~\u00a0\u00a0\u00a0 riga = riga.rstrip()<\/em>
\n~\u00a0\u00a0\u00a0 prl = riga.split()<\/em>
\n~\u00a0\u00a0\u00a0 # Guardian in a compund statement<\/strong><\/em>
\n~\u00a0\u00a0\u00a0 if len(prl) < 3 or prl[0] != ‘da’ :\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #be careful as it runs in order<\/em><\/strong>
\n~\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 continue<\/em><\/strong>
\n~\u00a0\u00a0\u00a0 print(prl[2])<\/em><\/p>\n
 <\/p>\n
#9 – dictionaries or Collections<\/h2>\n
list: linear collection of value (in order), index are [number]
\ndictionaries: “database” of value each with it’s own value (no specific order), index {word}
\nIf you look for a key that doesn\/t exist will result in TB<\/p>\n
~ create dictionaries<\/h3>\n
~x = dict()\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0\u00a0\u00a0 #create a dictionaries or you can use: x = { }<\/strong><\/em>
\n~x[‘pr’] = 3\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \u00a0 #add 3 and name it pr<\/em>
\n~x[‘dpp’] = 6\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \u00a0 \u00a0\u00a0 #add 6 and name it dpp<\/em>
\n~print(x)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #{‘pr’ : 3, ‘dpp’ : 6}<\/em>
\n~print(x[‘dpp’])\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \u00a0 \u00a0\u00a0 #6<\/em>
\n~x[‘dpp’] = x[‘dpp’] + 1 \u00a0\u00a0 #to edit dpp<\/em>
\n~print(x)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #{‘pr’ : 3, ‘dpp’ : 7}<\/em><\/p>\n
~ counting from string<\/h3>\n
~x = dict()<\/em>
\n~x[‘primo’] = 1<\/em>
\n~x[‘sesto’] = 1\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \u00a0 \u00a0 \u00a0 \u00a0\u00a0 #assign a number 1 to a word to start the count<\/em>
\n~print(x)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #x = {‘primo’: 1, ‘sesto’: 1}<\/em>
\n~x[‘sesto’] = x[‘sesto’] + 1<\/em>
\n~print(x)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #x = {‘primo’: 1, ‘sesto’: 2}<\/em><\/p>\n
on an existing one<\/p>\n
~x = dict()
\n~lista = [‘casa’, ‘topo’, ‘cane’, ‘topo’, ‘topo’]
\n~for nome in lista :
\n~\u00a0\u00a0\u00a0 if nome not in x:
\n~\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 x[nome] = 1
\n~\u00a0\u00a0\u00a0 else :
\n~\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 x[nome] = x[nome] + 1
\n~print(x)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #{‘casa’: 1, ‘topo’: 3, ‘cane’: 1}
\n<\/em><\/p>\n
~ get<\/h3>\n
Used to simplify if…else… <\/strong>with one line only<\/p>\n
~x = dict()
\n~lista = [‘casa’, ‘topo’, ‘cane’, ‘topo’, ‘topo’]
\n~for nome in lista :
\n~\u00a0\u00a0\u00a0 x[nome] = x.get(nome, 0) +1<\/strong>
\n~print(x)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #{‘casa’: 1, ‘topo’: 3, ‘cane’: 1}<\/em><\/p>\n
~ a counting pattern program in general<\/h3>\n
~x = dict()
\n~print (‘enter line of text:’)
\n~riga = input(‘ ‘)
\n~
\n~lista = riga.split()
\n~
\n~print(‘words:’, lista)
\n~
\n~print(‘counting…’)
\n~for nome in lista :
\n~\u00a0\u00a0\u00a0 x[nome] = x.get(nome, 0) +1
\n~print(x)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/em><\/p>\n
~ retrieving lists of keys<\/h3>\n
~x = {‘casa’: 1, ‘topo’: 3, ‘cane’: 1}<\/em>
\n~print(list<\/strong>(x))\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 \u00a0 \u00a0 \u00a0 # [‘casa’: 1, ‘topo’: 3, ‘cane’: 1]<\/em>
\n~print(x.keys{}<\/strong>)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 # [‘casa’: 1, ‘topo’: 3, ‘cane’: 1]
\n~print(x.values{}<\/strong>)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 # [1, 3, 1]
\n~print(x.items()<\/strong>)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 # [(‘casa’: 1), (‘topo’: 3), (‘cane’: 1)]<\/em><\/p>\n
~ two iteration variables<\/h3>\n
~x = {‘casa’: 1, ‘topo’: 3, ‘cane’: 1}
\n~for aa,bb in x.items() :
\n~\u00a0\u00a0\u00a0 print(aa, bb)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #[(aa: bb), (‘aa: bb), (aa: bb)]<\/em><\/p>\n
#a counting program with what we learned so far<\/h2>\n
~file = input(‘enter file:’)<\/em>
\n~handle = open(file)<\/em>
\n~<\/em>
\n~conto = dict()<\/em>
\n~for riga in handle:<\/em>
\n~\u00a0\u00a0\u00a0 nome = riga.split()<\/em>
\n~\u00a0\u00a0\u00a0 for parola in nome:<\/em>
\n~\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 conto[parola] = conto.get(parola, 0) +1<\/em>
\n~<\/em>
\n~grandeconto = None<\/em>
\n~grandeparola = None<\/em>
\n~for parola,conto in conto.items() :<\/em>
\n~\u00a0\u00a0\u00a0 if grandeconto is None or conto > grandeconto :<\/em>
\n~\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 grandeparola = parola<\/em>
\n~\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 grandeconto = conto<\/em>
\n~<\/em>
\n~print(grandeparola, grandeconto)<\/em><\/p>\n
 <\/p>\n
#10 – Tuples<\/h2>\n
Tuples are the fast and efficient counterparts of directories and lists, that is because they are immutable and therefore can’t be modified.
\nThey use () <\/strong>and they can also be more than one variable (on the left) like so (as long as the list on the right have the same number): (x, y) = (4, ‘tom’)
\n<\/em>Or in the case of directories they assume the pair (key and value for example).<\/p>\n
Tuples can be compared <> True False<\/strong> and it will do that by the first difference python finds (from left to right).<\/p>\n
~fhand = open(‘file.txt’)<\/em>
\n~cnt = dict()<\/em>
\n~for riga in fhand:<\/em>
\n~\u00a0\u00a0\u00a0 prle = line.split()<\/em>
\n~\u00a0\u00a0\u00a0 for pr in prle:<\/em>
\n~\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 cnt[pr] = cnt.get(pr, 0) +1\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #extrapolate each word<\/em>
\n~<\/em>
\n~lst = list()<\/em>
\n~for k, v in cnt.items() :<\/em>
\n~\u00a0\u00a0\u00a0 ntup = (v, k)<\/em>
\n~\u00a0\u00a0\u00a0 lst.append(ntup)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #create a tuple inside a dict word, word count with all the word<\/em>
\n~<\/em>
\n~lst = sorted(lst, reverse=True)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #reverse : word count, word<\/em>
\n~<\/em>
\n~for v, k in lst[:5] :<\/em>
\n~\u00a0\u00a0\u00a0 print(k, v)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #print top 5 used word and count<\/em><\/p>\n
simplified way
\n<\/em><\/p>\n
~fhand = open(‘file.txt’)<\/em>
\n~cnt = dict()<\/em>
\n~for riga in fhand:<\/em>
\n~\u00a0\u00a0\u00a0 prle = line.split()<\/em>
\n~\u00a0\u00a0\u00a0 for pr in prle:<\/em>
\n~\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 cnt[pr] = cnt.get(pr, 0) +1<\/em>
\n~<\/em>
\n~print( sorted( [ (v,k) for k,v in cnt.items() ] ) )\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #reduces the code lines<\/strong> <\/em>
\n~<\/em>
\n~for v, k in lst[:5] :<\/em>
\n~\u00a0\u00a0\u00a0 print(k, v)<\/em><\/p>\n
 <\/p>\n
#11 – Regular expression<\/h2>\n
Note: they are not essential for using python but it's worth knowing them\r\nI will eventually come back to them but for now:<\/pre>\n
Regular expression (regex or regexp) provide a concise way of looking for strings text files.
\nThey use their own characters and written in a formal language<\/p>\n
They are not part of standard python; to use them type import re<\/strong>
\nSome example : re.search()<\/strong> which is similar to find() and re.findall()<\/strong> combination between find() and slicing<\/p>\n
~Quick Guide for regex<\/h3>\n
https:\/\/www.py4e.com\/lectures3\/Pythonlearn-11-Regex-Handout.txt<\/p>\n
^\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #matches the beginning<\/em> of the line
\n$\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #matches the end<\/em> of the line
\n.\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #matches any<\/em> character
\n\\s\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #matches whitespaces<\/em>
\n\\S\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #matches any non whitespaces
\n<\/em>*\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #Repeats <\/em>a character zero or more times [longer string]
\n*? \u00a0 \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #Repeats <\/em>a character zero or more times (non-greedy) [shorter string]
\n+ \u00a0\u00a0 \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #Repeats <\/em>a character one or more times
\n+? \u00a0\u00a0 \u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #Repeats <\/em>a character one or more times (non-greedy)
\n[aeiou]\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #matches a single characther in the listed set<\/em> 
\n<\/em>[^XYZ]\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #matches a single characther not in<\/em> the listed set<\/em>
\n[a-z0-9]\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #the set of character can include a range<\/em>
\n(\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #indicates where string extraction<\/em> is to start
\n)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #indicates where string extraction<\/em> is to end<\/p>\n
wild card characters<\/p>\n
.*\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #matches any characters many number of time<\/p>\n
 <\/p>\n
#12 – Networked Programs<\/h2>\n
[6:22:40]<\/pre>\n
*Dr. Book on the subject: Introduction To Networking<\/pre>\n
 <\/p>\n
We operate on the Transport layer of the TCP\/IP protocol.
\nTCP connection, called also Sockets are the endpoint of the bidirectional inter-process communication flows across the internet.
\nTCP port number are basically extension of the process(eg: 10.10.10.10:80). There is a maximum of 65535 ports
\nThere are some common TCP ports such as:<\/p>\n
    \n
  • [21] FTP = File tranfer<\/li>\n
  • [22] SSH = Secure login<\/li>\n
  • [23] Telnet = Login<\/li>\n
  • [25] SMTP = Mail<\/li>\n
  • [53] DNS = Domain Name<\/li>\n
  • [80] HTTP<\/li>\n
  • [109\/110] POP = Mail Retrivial<\/li>\n
  • [143\/220\/993] IMAP = Mail Retrivial<\/li>\n<\/ul>\n
    ~Sockets in Python<\/h3>\n
    Python as built-in support for TCP sockets<\/p>\n
    ~import sockets\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #You need to import the library<\/em>
    \n~mysock = socket.socket(socket.AF_INET, socket.sock_stream)\u00a0\u00a0\u00a0\u00a0\u00a0 \u00a0 \u00a0\u00a0 #Create a socket<\/em>
    \n~mysock.connect( (‘data.py4e.org’, 80) )\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #Extend the socket (it can have no answer)<\/em><\/p>\n
    ~Application Protocol<\/h3>\n
    Application Layer1 –> Transport Layer1 —-> Transport Layer2 –> Application Layer2 [for transferring data]<\/p>\n
    Using HTTP (Read read the RFC to know the rules of the protocol)<\/p>\n
    ~Writing a Web Browser<\/h3>\n
    ~import socket<\/em>
    \n~<\/em>
    \n~mysock = socket.socket(socket.AF_INET, socket.sock_stream)
    \n~mysock.connect( (‘data.py4e.org’, 80) )
    \n~cmd = ‘GET http:\/\/data.py4e.org\/romeo.txt HTTP\/1.0\\n\\n’.encode()\u00a0\u00a0\u00a0\u00a0 #specified data to go accross
    \n~mysock.send(cmd)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #send data
    \n~
    \n~while True:\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #start receiving data
    \n~\u00a0\u00a0\u00a0 data = mysock.recv(512)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #at 512 characters per block
    \n~\u00a0\u00a0\u00a0 if (len(data) < 1):
    \n~\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 break\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #if data less than 1 means it’s done so break
    \n~\u00a0\u00a0\u00a0 print(data.decode())\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #print the decoded version of the data
    \n~mysock.close()\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #close the connection
    \n<\/em><\/p>\n
    ~Character and String<\/h3>\n
    Till now we used the ASCII (American Standard Code for Information Interchange) , which uses Latin characters.
    \nIt’s 1Byte or 8bits per character, and they are sorted by order.
    \nTo check the number value associate with each character (https:\/\/en.wikipedia.org\/wiki\/ASCII):
    \nprint(ord(‘H’))\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #72\u00a0\u00a0\u00a0\u00a0 H was assigned with number 72<\/em><\/p>\n
    Different from ASCII we have UNICODE which can represent every character on the world.
    \nthe problem is that uses UTF-32 Fix length for each character (4bytes or 32bits).
    \nThey were able to compressed down to UTF-16 fixed length (2bytes) although still too large.
    \nAnd finally we have UTF-8 with uses dynamic length, from 8 to 32bits. Because of that it also compatible with ASCII and is the most used on the web.<\/p>\n
    Because we are sending bytes, when we are working with Python we need to encode <\/strong>(in UTF-8) data to send, and when we receive data we need to\u00a0decode\u00a0<\/strong>before printing them.
    \nstring –encode–><\/strong> bytes\u00a0\u00a0\u00a0\u00a0\u00a0 ||\u00a0\u00a0\u00a0\u00a0 bytes –decode–><\/strong> string<\/em><\/p>\n
    ~urllib (easier HTTP)<\/h3>\n
    ~import urllib.request, urllib.parse, urllib.error\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #import libraries<\/em>
    \n~<\/em>
    \n~fhand = urllib.request.urlopen(‘http:\/\/data.py4e.org\/romeo.txt’)\u00a0\u00a0\u00a0\u00a0 #open, encode and loop<\/em>
    \n~for line in fhand:<\/em>
    \n~\u00a0\u00a0\u00a0 print(line.decode().strip())\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #decode the received data<\/em><\/p>\n
    you can also use it for .html to read web pages<\/p>\n
    ~import urllib.request, urllib.parse, urllib.error\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 <\/em>
    \n~<\/em>
    \n~fhand = urllib.request.urlopen(‘http:\/\/data.py4e.org\/romeo.html<\/strong>‘)\u00a0\u00a0 <\/em>
    \n~for line in fhand:<\/em>
    \n~\u00a0\u00a0\u00a0 print(line.decode().strip())
    \n<\/em><\/p>\n
    ~web scraping or crawling<\/h3>\n
    Note: be carefull as not every site allow you to use a program to watch their website<\/p>\n
    Beautiful Soup <\/strong>is a program that crawl the pages. It compensate all the error can occurr by retriving webpages.
    \nNote: Beutiful soup has to be installed ( https:\/\/pypi.python.org\/pypi\/beautifulsoup4 )<\/p>\n
    ~import urllib.request, urllib.parse, urllib.error\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #import libraries<\/em>
    \n~from bs4 import BeautifulSoup\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #import BS
    \n~
    \n~url = input(‘Enter -‘)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #url to crawl
    \n~html = urllib.request.urlopen().read()\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #open and read the html
    \n~soup = BeautifulSoup(html, ‘html.parser’)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #retrive data trough BS
    \n~
    \n~tags = soup(‘a’)\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0 #retrive anchor tags
    \n~for tag in tags:
    \n~\u00a0\u00a0\u00a0 print(tag.get(‘href’, None))<\/em><\/p>\n
     <\/p>\n
    #13 – Using Web Servicies<\/h2>\n
    [7:24:10]<\/pre>\n
    To be continued............<\/pre>\n","protected":false},"excerpt":{"rendered":"
    PY4E – Python For Everybody Learning Python with Dr.Chuck free course First of all I would like to thank D. Chuck for sharing his knowledge by creating this free online […]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"iawp_total_views":16,"footnotes":""},"categories":[33,19,37],"tags":[36,34,20],"class_list":["post-163","post","type-post","status-publish","format-standard","hentry","category-python","category-software","category-study-notes","tag-code","tag-python","tag-software"],"_links":{"self":[{"href":"https:\/\/paradoxa.me\/index.php\/wp-json\/wp\/v2\/posts\/163","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/paradoxa.me\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/paradoxa.me\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/paradoxa.me\/index.php\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/paradoxa.me\/index.php\/wp-json\/wp\/v2\/comments?post=163"}],"version-history":[{"count":43,"href":"https:\/\/paradoxa.me\/index.php\/wp-json\/wp\/v2\/posts\/163\/revisions"}],"predecessor-version":[{"id":223,"href":"https:\/\/paradoxa.me\/index.php\/wp-json\/wp\/v2\/posts\/163\/revisions\/223"}],"wp:attachment":[{"href":"https:\/\/paradoxa.me\/index.php\/wp-json\/wp\/v2\/media?parent=163"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/paradoxa.me\/index.php\/wp-json\/wp\/v2\/categories?post=163"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/paradoxa.me\/index.php\/wp-json\/wp\/v2\/tags?post=163"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}