About generator in Python

Question

def fib(max):
    n, a, b = 0, 0, 1
    while n < max:
        yield b
        a, b = b, a + b
        n = n + 1     
    return 'done'

print(next(fib(6)))
print(next(fib(6)))
print(next(fib(6)))

the result is 1，1，1. However, if I change the content in print() as below:

f = fib(6)
print(next(f))
print(next(f))
print(next(f))

the result will be 1, 1, 2. Why does this happen?

You create new generators each time. You do see that difference, don't you? — Martijn Pieters, Jan 15 '17 at 14:19
You might also want to remove the 'done' following your return statement... — José Sánchez, Jan 15 '17 at 14:25
@Rawing thank U for your advice.Thanks to Jim who had already helped me improve my question. I will notice it next time:) — Eva Red, Jan 15 '17 at 16:03

Dimitris Fasarakis Hilliard · Accepted Answer · 2017-01-15T14:27:16.743

The call print(next(fib(6))) always creates a new instance of the fib generator and yields one value from it, you then discard it.

On the other hand:

f = fib(6)
print(next(f))
print(next(f))
print(next(f))

creates an instance f of the generator fib and yields three values from it.

Also, using max as the parameter name is frowned about since, in the local scope at least, you're masking a built-in function that has the same name.

About generator in Python

1 Answers1