In Python you can define conditional statements, known as if-statements. A block of code is executed if certain conditions are met.

Related Course:
Practice Python with interactive exercises

If statements

Consider this application, it executes either the first or second code depending on the value of x.

#!/usr/bin/python
x = 3
if x > 10:
    print("x smaller than 10")
else:
    print("x is bigger than 10 or equal")

If you set x to be larger than 10, it will execute the second code block.   We use indentation (4 spaces) to define the blocks.

A little game: A variable may not always be defined by the user, consider this little game:

age = 24
print "Guess my age, you have 1 chances!"
guess = int(raw_input("Guess: "))
if guess != age:
    print("Wrong!")
else:
    print("Correct")

Conditional operators

A word on conditional operators Do not confuse the assignment operator (=) with the equals operator (==).

Nesting

The most straightforward way to do multiple conditions is nesting:

a = 12
b = 33
if a > 10:
    if b > 20:
        print("Good")

This can quickly become difficult to read, consider combining 4 or 6 conditions.  Luckily Python has a solution for this, we can combine conditions using the and keyword.

guess = 24
if guess > 10 and guess < 20:
    print("In range")
else:
    print("Out of range")

Sometimes you may want to use the or operator.

Operator	Description
!=	not equal
==	equals
>	greater than
<	smaller than