A cheat sheet for Python I made a while ago.

python_cheat_sheet.py

#Python Cheat Sheet

#Any thing preceded by a '#' is a comment and won't be executed like this line here

#Variables are names defined by the programmer that hold values
WonderfulVariableByMe = 5
#There are some reserved words like: for, if, def, while, break, ... that cannot be used to name a variable
#A variable name must not contain spaces and must never start with a number
#Variable names are case-sensitive: modar does not equal Modar

#Variable values can be 
# Single Values:
# 	1- linear: 
#		An integer 5, 4, 0, -4, ...
#		A floating point number 2.5, -2.6, 14.0, ...
#		A character 'a', 'A', 'e', ... 
#			Think how can we represent a single quote character ' 
# 	2- boolean:
#		Either (True or False) or (1 or 0)
# 	3- string:
#		A sequence of characters with the help of escape character you can represent any text
#		\'	single quote
#		\"	double quote
#		\\	backslash
#		\n	new line
#		\r	carriage return
#		\t	tab
#		Important: Visit [http://www.tutorialspoint.com/python/python_strings.htm]
#		for more information on accessing values in strings and some common strings operations
print 'Modar\\genius' #prints: Modar\genius
print 'Modar is \'Genius\'' #prints: Modar is 'Genius'
print 'Modar \nis \nGenius' #prints in separate lines: Modar is Genius
#	4- function: forget about it now
#	5- class object: more details later
# Multiple Values:
# 	6- list
# 	7- tuple
# 	8- dictionary
#	Important: Visit [http://www.tutorialspoint.com/python/python_variable_types.htm]
#	and only read python lists, python tuples, python dictionary

#Arithmetic operators
#	The usual arithmetic we know: +, -, *, /, ...
x = 5
y = 7
z = x * y
print z #prints: 35

#comparison operators
#	Used to compare values and always return boolean (either True or False):
#		== is equal
#		!= is not equal (sometimes we use <> instead of != although they have same meaning)
#		<  less than
#		>  greater than
# 		<= less than or equal
#		>= greater than or equal
#		in is value in list
#		is are they the same
a = 1
b = 2
c = 1
s = [1, 3, 4]

x = a == b #x = False
x = a != b #x = True
x = a is c #x = False (Although they have the same values but a is not the same as c)
x = b <  a #x = False
x = a >  7 #x = False
x = a <= b #x = True
x = a >= c #x = True (since they are equal)
x = a in s #x = True (since 1 is an element in s) 

#combining boolean expressions
#	and
#	or
# 	not
x = (a < b) and (b < c) #x = False because one of the conditions is false
x = (a < b) or (b < c)  #x = True because one of the conditions is true
x = not (a < b) #x = False because (a < b) is True; and not True is False

#Decision Making:
#	using if condition
if a < b:
	print 'Yes, a is less than b'
#	Note: the colons ':' and the indentation before print
if a > b:
	print 'Yes, a is less than b'
print 'Modar'
#	Modar will be printed regardless of whether the condition is satisfied or not
#	because it is not part of the condition and we know that by the indentation
#	You can also nest conditions as you want:
if a < b:
	print 'Yes, a is less than b'
	if b > 10:
		print 'And b is greater than 10'

#	The full syntax of if conditions
if a == b:
	print 'a equal b'
elif a < b:
	print 'a is less than b'
else:
	print 'a is greater than b'
#	elif means else if which means if all above conditions were not satisfied  
#	You can add as many elif as you want
if a < b:
	print 'ddd'
elif b > c:
	print 'eee'
elif c > a:
	print 'hhh'

#Loops: you can find tutorial on loops at the end of this document
#	while loop
while a < 10:
	print 'a is still less than 10'
	a = a + 1
print 'now a is equal to 10'

#	for loop
myList = [5, 7, 6, 3]

#	to print all elements of myList
for a in myList:
	print a

#	to reach elements in the list
for i in range(len(myList)):
	myList[i] = myList[i] + 1
print myList

#You can also nest loops
lol = [[1,2,3],[4,5,6],[7,8,9]]
for x in lol:
	for y in x:
		print y
#this will print all elements of all lists in lol

#Functions
#	functions are piece of code that take input(s) and return output
#	This function takes any number and returns the next number
def func(input):
	a = input + 1
	return a
# 	to use it
n = 5
next = func(n)
print next

#	it can take many input
def add(x, y):
	a = x + y
	return a
print add(1, 2) #prints: 3
print add(10, 5) #prints: 15

#or it can take no input
def prnt():
	print 'function that takes no input and return nothing'
prnt() #this will print the sentence above

#Classes
#	You don't have to concern yourself too much with classes
#	All what you need to know is that you can think of them as libraries of function
#	E.g. the class named math has a lot of functions like sin and cos
#		 [this is not 100% accurate but you can think of it like that]
import math
x = math.sin(maht.pi/2) # x = 1 because sin(pi/2) is one

#----------------------------------------------------------------------------------------------------------
#Loops Tutorial
#	The most basic loop is while loop
while a != 10:
	print 'a is still not equal to 10'
	a = a + 1
print 'now a is equal to 10'
#	while loop will keep looping as long as the condition is satisfied
#	some wile loop will loop forever because the condition can never be satisfied
while a == 0:
	print 'a is still not equal to 0'

#	It is a common thing that we sometimes need to go through all elements of a list
myList = [5, 2, 6, 1, 8]

listLength = len(myList)
i = 0
while i < listLength:
	a = myList[i]
	print a
	i = i + 1
#	The previous code took 6 lines of code and this become tedious if because we need that a lot

#	sometimes we need to go through all elements but we also need to modify them
i = 0
while i < listLength:
	a = myList[i]
	a = a + 1
	i = i + 1
print myList
#	this will print the old list as is and will not change any value
#	because (a) takes a copy of the element and not the element itself
i = 0
while i < listLength:
	myList[i] = myList[i] + 1
	i = i + 1
print myList #prints: [6, 3, 7, 2, 9]

#	Since working with list is tiresome, the introduction of a new kind of loop helped us a lot; for loop
for a in myList:
	print a
#	and that is it only two lines to print the content of the list

#	to modify the list we cannot do the following
for a in myList:
	a = a + 1
print myList
# 	because a is a copy and not the element itself. Instead, we do this
r = [0, 1, 2, 3, 4]
for i in r:
	myList[i] = myList[i] + 1
print myList
# 	this is better but also tiresome because you need additional list from 0 up to the length of your list
#	so python has provided us with a really nice function called range
r = range(5) # r = [0, 1, 2, 3, 4]
for i in r: 
	myList[i] = myList[i] + 1
print myList
#	or even better
for i in range(listLength): 
	myList[i] = myList[i] + 1
print myList

#----------------------------------------------------------------------------------------------------------
#Extras
#	List comprehension [Set Notation]
#	you can loop through all the elements of a list and apply some operations on them to construct a new list
myList = [2,1,5,6,8,9,4]
incrementedList = [element+1 for element in myList] # [3,2,6,7,9,10,5]
#	you can also apply conditions and do a lot of stuff with it like thresholding
thresholdedList = [element for element in myList if element>0 and element<5]