30. Generator functions

Avoid generating large number of values or objects as they may take up memory. Use yield inside a function to generate values or objects as needed. Functions generating collections using yield are more space efficient and faster.

30.1. Don’t do this

def generate_sequential_numbers(n):
    nums = []
    for i in range(n):
        nums.append(i)
    return nums

sum(generate_sequential_numbers(10000000))

30.2. Do this

def generate_sequential_numbers(n):
    for i in range(n):
        yield i

sum(generate_sequential_numbers(10000000))

generate_sequential_numbers = lambda n: (i for i in range(n))

sum(generate_sequential_numbers(10000000))