Function to find all permutations of a given string

allPermutations.py

#########################################################################
# Finds all permutations of a given string by using a tree-structure    #
# It sets two counters, i and j with 0 < i <= j < length(string)        #
# While keeping i fixed, iterates j through the remaining characters,   #
# swapping each one with the character at i and adding it to a list     #
# if the new string isn't on the list. Example shown below for 'abc'    #
#                                                                       #
#                                   (abc)                               #
#                                |    |   |                             #
#                            |        |      |                          #
#                        |            |           |                     #
#                     |               |               |                 #
#                   (abc)           (bac)           (cba)               #
#                   |   |           |   |           |   |               #
#               (abc)   (acb)   (bac)   (bca)   (cba)   (cab)           #
#                                                                       #
#########################################################################


def search(list, platform): # Find out if given string/number is in list
    for i in range(len(list)):
        if list[i] == platform:
            return True
    return False

def swap(s, pos1, pos2): # Swap characters of a string
    str_list = list(s)
    d1 = str_list[pos1]
    str_list[pos1] = str_list[pos2]
    str_list[pos2] = d1

    return "".join(str_list)

def permutations(string):
    perms = [string]    # List to store all permutations
    for k in perms:     # Iterate through current permutations
        for i in range(0, len(string)): #Original char to swap
            for j in range(i, len(string)): #Secondary char to swap
                temp = swap(k, i, j)
                if not search(perms, temp):
                    perms.append(temp)
    return perms



s = "abcd"
x = permutations(s)
#x.sort()