Erle Robotics Learning Python GitBook Free

Conditional statements

if is a conditional statement that executes some specified code after checking if its expression is True.

Practice 1

Run this code and see what happend:

>>> x=10
>>> if x>2 :
...     print "It is a Large number."
...
It is a Large number.

Note, the identation is very important here.

The else statement complements the if statement. An if/else pair says: "If this expression is true, run this indented code block; otherwise, run this code after the else statement."

Unlike if, `else doesn't depend on an expression.

Practice 2

Let's see an example:

>>> if 8 > 9:
...     print "I don't printed!"
... else:
...     print "I get printed!"
...
I get printed!
>>>

elif is short for "else if." It means exactly what it sounds like: "otherwise, if the following expression is true, do this!"

Practice 3

Here you find the example:

>>> if 8 > 9:
...     print "I don't get printed!"
... elif 8 < 9:
...     print "I get printed!"
... else:
...     print "I also don't get printed!"
...
I get printed!