For loop only executes 1 time, though given a range of 5

问题

I have the following code:

def input_scores():
scores = []
y = 1
for num in range(5):
    score = int(input(print('Please enter your score for test %d: ' %y)))

    while score < 0 or score > 100:
        print ('Error --- all test scores must be between 0 and 100 points')
        score = int(input('Please try again: '))
    scores.append(score)
    y += 1
    return scores   

When I run it, the output is as follows:

Please enter your score for test 1: 
None

Then I'll enter the test score next to None, as, say 95 It then runs through the rest of the program without prompting me for the next test score to add to the scores list. I'm really curious why that is

Thanks in advance for taking the time to help

Sincerely, ~Dustin

回答1:

your return statement is indented too much, causing the function to return on the first iteration. It needs to be outside of the for block. This code works:

def input_scores():
    scores = []
    y = 1
    for num in range(5):
        score = int(input('Please enter your score for test %d: ' %y))
        while score < 0 or score > 100:
            print ('Error --- all test scores must be between 0 and 100 points')
            score = int(input('Please try again: '))
        scores.append(score)
        y += 1
    return scores

回答2:

You return from inside the loop. Move return scores one indent left.

回答3:

You indentation of the code seems whacky. It looks like the return statement is inside the scope of the for loop. So after the first iteration the return statement takes you out of the function completely.

回答4:

You're returning scores at the end of each loop iteration (so in other words, after the first loop iteration finishes, you return all the scores thereby exiting the function, and the loop).

Change your code to be:

for num in range(5):
    # ...
return scores    # Note the indentation is one tab less than the loop's contents

回答5:

Others have correctly pointed out that the indentation of your return statement was causing the problem. Also, you might want to try it like this, using len(scores) to control the loop, as @max suggested:

def input_scores(num_tests=5, max=100, min=0):
    scores = []
    while len(scores) < num_tests:
        score = int(input('Please enter your score for test {0}: '.format(len(scores)+1)))
        if score < min or score > max: 
            print ('Error --- all test scores must be between 0 and 100 points.')
        else:
            scores.append(score)
    return scores

来源：https://stackoverflow.com/questions/9970005/for-loop-only-executes-1-time-though-given-a-range-of-5