Weaving Numbers In Python

I am trying to write a code which returns a list of all possible woven numbers from two user inputted numbers. For Example,

if A = 27 and B = 54 then there are four numbers that can be woven

2574

5247

7425

4752

Weaving a number can be done by weaving from the beginning, starting with A, weaving from the beginning, starting with B, weaving from the end, starting with A, weaving from the end, starting with B. While weaving two numbers A and B, if all the digits of A are weaved and some more digits are there in B, the remaining digits of B are just appended at the end.

I am trying

num_a = input()
num_b = input()
weaved_nums = []

def permutations(string):
    if len(string) == 1:
        return string

    recursive_perms = []
    for c in string:
        for perm in permutations(string.replace(c,'',1)):
            recursive_perms.append(c+perm)

    return set(recursive_perms)

num_a_perms = list(permutations(num_a))
num_b_perms = list(permutations(num_b))

def weave(num_1, num_2):
    new_string = ''
    for i in range(len(min([num_1, num_2], key = len))):
        new_string += num_1[i] + num_2[i]
    new_string += max(num_1, num_2, key=len)[len(num_1):]
    weaved_nums.append(new_string)

for i in range(len(num_a_perms)):
    for k in range(len(num_b_perms)):
        weave(num_a_perms[i], num_b_perms[k])
        weave(num_b_perms[k], num_a_perms[i])
        

print(weaved_nums)

However my program returns

['2475', '4257', '2574', '5247', '7425', '4752', '7524', '5742']

for inputs 27 and 54