Good. Now, let's introduce if statements. They are used to check some conditions and execute different parts of code depending on the results of these conditions:

john_age = 25
user_age = input('How old are you?')

if int(user_age) > john_age:
  print('You are older than John.')

1. We started line #4 with the if keyword.
2. After a space, we provided the condition: user_age must be greater than john_age (recall that user input is always treated as string, so we had to convert user_age to int).
3. After the condition, we need a colon (:).
4. On line #5, we wrote the instruction that should be executed when the condition is met (i.e., when user_age > john_age returns True).

Note that indentation is very important in Python. The code to be executed when the condition is met (i.e., the code after if) must be indented – the lines after if must start with a certain number of spaces (1 or more) or tabs. You can choose any of the two styles, but you have to be consistent.

The PEP8 (Python Enhancement Proposal 8 – the document that gives coding conventions for Python) proposes to use four spaces per indentation level.