Python 3 - Second Edition

21.4    Generators as Consumers

In Section 21.1, you learned about generators. Generators are special functions that return multiple values in succession so that iteration can be performed over them.

The following example generator generates the first n square numbers:

def square_generator(n):    for i in range(1,n+1):        yield i*ifor q in square_generator(3):    print(q)  

This sample program outputs the numbers 1, 4, and 9 on the screen. Each for loop uses the iterator protocol, so the second for loop in the example is semantically equivalent to the following program:

g = square_generator(3)try:    while True:        v = next(g)        print(v)except StopIteration:    pass  

Here, a generator instance g is created first, and then the next value is read with next(g) until ...