在python 2.7中有time.sleep的问题

Question

I'm running this very simple function for testing:

import time
def printnum(ang):
    if ang > 0:
        print(ang)
        time.sleep(3 * abs(ang) / 360)
        print("done")
    if ang < 0:
        print(ang)
        time.sleep(3 * abs(ang) / 360)
        print("done")

When I run it on python 3 it works fine However, on python 2 I get an issue where printnum doesn't work on a wide range of numbers, it doesn't perform the delay... In fact, so far it has only worked with printnum(180) in my tests.

This is weird for a code that is so simple. I've tested on 2 computers. Does it happen to you? Any reason why? Suggestions to make it work? (Other than moving to python 3 which is hard on the hardware I'm working with)

Answer 1

On Python 2, / defaults to truncating integer division when passed int operands, not "true division" (which produces float results). You can fix in one of two ways:

1. Add from __future__ import division to the top of the file to use Python 3 division rules ( / means true division always, where you use // if you really mean floor division)
2. Change either 3 or 360 to float literals so the math is performed float -style, eg time.sleep(3. * abs(ang) / 360) or time.sleep(3 * abs(ang) / 360.)

Answer 2

since ang is probably an integer small enough then 3 * abs(ang) / 360 is an expression where one integer divides another.

Python 2 division is integer division by default so the result is probably 0.

Fix:

3.0 * abs(ang) / 360