Shuffle a python list without using the built-in function

问题

I'm working on writing two different shuffle functions.

The first shuffle function must take a list and return a new list with the elements shuffled into a random order.

This is what I have so far for the first shuffle function-

def shuf(List):
    import random
    newList=[]
    for i in List:
        i=random.randrange(len(List))
        newList+=i
    return newList

The second shuffle function takes a list as a parameter and shuffles the list in place.

I know how to do it with the built-in function but I'm not allowed to use it.

回答1:

You might find that this implementation for shuffling suits your needs. Make sure that you note the difference between the two functions before using them.

import copy
import random


def main():
    my_list = list(range(10))
    print(my_list)
    print(shuffle(my_list))
    print(my_list)
    shuffle_in_place(my_list)
    print(my_list)


def shuffle(container):
    new_container = copy.copy(container)
    shuffle_in_place(new_container)
    return new_container


def shuffle_in_place(container):
    for index in range(len(container) - 1, 0, -1):
        other = random.randint(0, index)
        if other == index:
            continue
        container[index], container[other] = container[other], container[index]


if __name__ == '__main__':
    main()

回答2:

Plan: Go through the list from the beginning starting with element 0; find a new random position for it, say 6, put 0’s value in 6 and 6’s value in 0. Move on to element 1 and repeat this process, and so on through the rest of the list

import random
iteration = random.randint(2, 100)
temp_var = 0
while iteration > 0:
    # We will be swapping the value of i for j.
    # And then setting j to what i was using the temp_var place holder.
    for i in range(1, len(my_list)): # have to use range with len()
        for j in range(1, len(my_list) - i):
            # Using temp_var as my place holder so I don't lose values
            temp_var = my_list[i]
            my_list[i] = my_list[j]
            my_list[j] = temp_var

        iteration -= 1

来源：https://stackoverflow.com/questions/17489477/shuffle-a-python-list-without-using-the-built-in-function