7.5 Designing with Functions

Notes

Break programs into small functions, each with one clear purpose, and give them descriptive names.

• Write a function when you repeat the same steps or when a task can be named clearly.
• Functions can call other functions.

def is_even(n):
return n % 2 == 0

def describe(n):
if is_even(n):
return "even"
return "odd"

print(describe(7))

• is_even(7) is False, so describe(7) returns odd and the program prints odd.
• A function returning True or False is often called a predicate.
• Test each function on its own with several inputs, including edge cases like 0.