BASICS

–  Getting Help :  help(‘for’), help (‘import’), help(‘replace’) , a.replace?

–  Getting Help :  pydoc ( documentation module for python comes with python installation , search for python documentation  or generate html for documentation purpose)  :   ubuntu prompt : $  pydoc for

–  IDE ( Pycharm , )

–   IDE (Jupyter QT console )  – you can get prompts for auto complete methods, example dir(a) live give all methods available for that object )

–  Comments  ( # Single, “””” Triple Quotes for multiple lines “”””)

–  Literal Constants  –  Number or Strings is a Value

–  Types of Numbers

    –  Integers ( Example 0, 1, 23232, -22 ) , 

       Dividing Integer by Integer will give only integer part of the component , Implemented as C longs.  Inorder to return a decimal convert one of the numbers to  decimal  example … 3/2 = 1   and 3/2.0 = 1.5

       A number preceding with a 0 , example 015 is an OCTAL number )  so  5= 05 will return true , but  12 = 012 will not return true

    –  Long Intergers  –  Example   324342234324L  , represented by an I or L at the end

    –  Floating point numbers = >  examples  1.0 , 1.2e-2,  1.1e10,  8.99E4 

       Implemented as C doubles, 

       Returns a float if operations involve number and float ( general tendency is that the when calculation is done for 2 numbers, the most complex form datatype result is obtained )

    –   Octal, Hex constants   ( Octal must start with 0 example 02, Hex must start with 0x examples  0x1ff )

    –    Complex numbers  ( Example  ( 1 + 3j ),  2.0 + 4.0j    ,   always needs to end with a j or J

Python Identifiers 

–    Variables start with A – Z, a -z,   0 or _  ,  CASE SENSITIVE ,   CANNOT have special characters   @, $, % within identifiers, NO DECLARATION of datatype is required.

–    Naming convention  ( Class names start with  upper case and all other lower case ),  STARTING WITH _ indicates the identifier to be PRIVATE, starting with 2 leading underscore indicates that the identifier is STRONGLY PRIVATE,  starting with 2 underscores and ending with 2 ending underscores  LANGUAGE DEFINED special name

–     

Operations on Numbers 

– Arithmetic operators :  a+b, a-b, a/b, a*b

– Modulo :  a%b

– Exponent :  a**b

–   Other elementary numbers not defined in python but in packages like NumPy and SciPy

–  Order of operations is PEMDAS ( Parentheses, Exponents, Multiplication, Division, Addition, Subtraction )

Comparison Operators

 –  a < b ,  a > b , a >= b, a <= b

– Identity tests =>   a == b , a != b 

Bitwise Operators 

–   OR  ( a | b ),  AND (  a & b ) ,  XOR ( a ^ b )

–  Shift bits   LEFT (  a << b ), RIGHT ( a >> b )

Operations on String

–  Python does not support character, even a single letter is treated as a string, 

–  Separation of space will give you ( list of strings ) , example ,  a = ” This is a string ” , a[0] = This,  a[1]= Space a[2] = is

–  String are immutable 

–  Can be defined by a  single or double quote , Double lets you expand the string across multiple lines 

–  String are added by +     ‘abc’ + ‘abc’ = abcabc

–  Strings are multiplied by  ‘abc’ * 3 = ‘abcabcabc’

–  Create a multi line string , use a  \ at the end of the line of the string

–  String Slicing, Indexing  :  a = ” This is a string” ,   a[:3] = “Thi” , a[-1]= “g”, a[2:4] = “is”   ,  Index starts at 0,   [i] get the  i’th letter from the string

–  Membership checking :  in, not in operator    ‘is’ in a   ‘strings’ not in a

–  Formatting Strings using %:   d = ” This is %s, and she is %d years of age” %(‘Tom’, 18 )

–  Functions 

    .capitalize ( Capitalize the first character ),  count( # of times string occurs ), index ( similar to find(), first position of the found string ),  index raises an error but find() does not

     encoding and decoding :  s.encode(encoding=”UTF-8″, errors=’strict’)  , By default in python 3 encoding is UTF-8

     max(), min(), replace(), upper()

Indentation

–   Important in Python, used to identify group of statements,  can be done by adding spaces or tabs

–   its a MUST, as there are no braces

–   Group of statements must be indented by the same amount, the standard indentation is 4 characters.