Python

Indentation

Python is an indented language, so the code indentation matters. A good practice is to indent with 4 spaces (if you mix spaces and tabs the code won't work.

Operators

Arithmetic

+    Addition
-    Substraction
*    Multiplication
/    Division
**   Power
%    Reminder
//   Floor division (Reminder is removed)

Comparison

==   Equal 
!=   Not equal
>    Greater
>=   Greater or equal
<    Smaller
<=   Smaller or equal
<>   Similar to !=

Assignment

=    Simple assignment
+=   Add and as
-=   Substract and  assignment
*=   Multiply and assignment
/=   Divide and assignment
%=   Modulus and assignment
**=  Exponent and assignment
//=  Floor Divisionn and assignment

Bitwise operators

They perform operations on binary terms. a= 8 → 100; b= 9 → 101; a & b → 100

$    Binary AND
|    Binary OR
^    Binary XOR
~    Binary complement
<<   Binary left shift
>>   Binary right shift

Logic

and
or
not

Membership operators

in
not in

Variables

String

String assingment:
MyString = 'Hello World' OR MyString = "Hello World"
Strings can be subset sliced:

MyString = "Hello world"
MyString[0:4]

Hel

in operator: to check if a substring is contained in a string

String library:

str.lower()
str.upper()
str.capitalize() → Uppercases 1st char
str.center(width[, fillchar])
str.startswith(preffix[, start[, end]])
str.endswith(suffix[, start[, end]])
str.find(substring[, start[, end]])
str.lstrip([chars])
str.rstrip([chars])
str.strip([chars])
str.replace(old, new[, count])

len(MyString) → returns the lenght of a string

Collections

Dictionary

Key - Value pairs,

Conditional

if/elif/else

if a < 10:
    print "Less than 10"
elif a >= 10 and a < 20:
    print "a greater or equal to 10 and less than 20"
else:
    print "a greater or equal to 20"

try/except/finally

try:
    file = open("test.txt")
except:
    print "Could not open file"
finally:
    print "This part will be executed at the end whether the open fails or not"

Loops

For

NumberList = [1, 3, 7, 12, 24]
for number in NumberList:
    print number

Another way:

for i in range(0, len(NumberList)-1):
    print NumberList[i]

while

CtrlNum = 7
while CtrllNum > 3:
    print CtrlNum
    CtrlNum -= 1

Functions

All arguments in Python are passed by reference, if you change a variable value inside a function it will be changed at the calling function.

def MyFunction(formal_arg, optional_arg = None, *variable_lenght_args):
    print formal_arg
    if optional_arg:
        print optional_arg
    for arg in variable_lenght_args:
        print arg