Python generator yields same value each call

问题

I want this generator to yield the cosine of each successive value from a list, but am getting the same value each time.

import math     
angles = range(0,361,3)

# calculate x coords:    
def calc_x(angle_list):
    for a in angle_list:
        yield round(radius * cos(radians(a)), 3) 

Yields the same value with each call: Why is this and how do I fix it?

>>>calc_x(angles).next()
5.0
>>>calc_x(angles).next()
5.0
>>>calc_x(angles).next()
5.0

回答1:

Every time you call calc_x you create a new generator. What you need to do is create one and then keep using it:

calc = calc_x(angles)
next(calc)
next(calc)
# etc.

来源：https://stackoverflow.com/questions/15216972/python-generator-yields-same-value-each-call