Small Functions.

Fourth class. A large task is easier to read when you split it into small, clearly named functions.

def base(n):
    return n * 2

def bonus(n):
    return n + 1

def total(n):
    return base(n) + bonus(n)

Each function does one job. total assembles the parts. That makes fixing and checking calmer.

Common mistake: one huge function with everything inside; or copying the same formula in three places instead of a helper.