为什么我的 while 循环有时会卡住，但有时不会在我的“秘密圣诞老人”程序中？

Question

im trying to create basic secret santa function where u can pass list of names to it and it will automaticlly generate random possibilites but while loop sometimes gets stuck and that's the weird part i can not understand why.

def santa(listi):
    from random import shuffle,choice
    my_dict = {}
    shuffle(listi)
    while len(my_dict) != len(listi):
        person = choice(listi)
        person2= choice(listi)
        if person!= person2 and person2 not in my_dict.values() and person not in my_dict.keys():
            my_dict.update({person:person2})
        else:
            continue
    return my_dict

Answer 1

So whats happening is sometimes it ends up in the case where one person (for example below person "Y") is the receiver and giver of the gift:

<class 'list'>: ['X', 'W', 'Y', 'Z']
<class 'dict'>: {'X': 'W', 'Z': 'X', 'W': 'Z'}

I ran your code several times in the PyCharm debugger before I got to this case. Your while loop condition is:

while len(my_dict) != len(listi):

and as you can see this will never be the case as your code is now locked as the if condition person != person2 will never be passed.

You should take a look at your if condition again and if you cant figure it out mention me in a comment and I'll help you out. A good idea would be to check what possible combinations are left and if only the condition above is met ie Y is the receiver and giver, discard the list and keep going. This will guarantee you will always exit but is by no means optimal.