14. Iterators & Generators

Lazy Evaluation

What if you need to process 1,000,000,000 rows? A list will crash your RAM. A Generator produces one item at a time.

The yield keyword

Functions that return die. Functions that yield pause.

python
def infinite_numbers():
    n = 0
    while True:
        yield n
        n += 1

gen = infinite_numbers()
print(next(gen)) # 0
print(next(gen)) # 1