精簡版從python中的函數返回時為空

Question

問題是為什么變量測試為空？ 程序將返回正確排序的數組。 但似乎沒有得到分配。

def my_sort(array_to_sort):
    sort = False
    number_of_items = len(array_to_sort)
    print "sorted array: ", array_to_sort

    for i in range(0, number_of_items-1):
        if array_to_sort[i] > array_to_sort[i+1]:
            tmp = array_to_sort[i]
            array_to_sort[i] = array_to_sort[i+1]
            array_to_sort[i+1] = tmp
            sort = True
    if sort == True:
        my_sort(array_to_sort)
    elif sort == False:
        return array_to_sort

if __name__ == '__main__':
    # main()

    arr = [4,5,7,3,2,1]
    test = my_sort(arr)
    print (test)

這將返回以下內容。

sorted array:  [4, 5, 7, 3, 2, 1]
sorted array:  [4, 5, 3, 2, 1, 7]
sorted array:  [4, 3, 2, 1, 5, 7]
sorted array:  [3, 2, 1, 4, 5, 7]
sorted array:  [2, 1, 3, 4, 5, 7]
sorted array:  [1, 2, 3, 4, 5, 7]
None

Answer 1

您忘記了第一個條件的回報：

if sort == True:
    return my_sort(array_to_sort)

同樣，您也不需要將布爾值與布爾值進行比較。 您的代碼應如下所示：

def my_sort(array_to_sort):
    sort = False
    number_of_items = len(array_to_sort)
    print "sorted array: ", array_to_sort

    for i in range(0, number_of_items-1):
        if array_to_sort[i] > array_to_sort[i+1]:
            tmp = array_to_sort[i]
            array_to_sort[i] = array_to_sort[i+1]
            array_to_sort[i+1] = tmp
            sort = True
    if sort:
        return my_sort(array_to_sort)
    else:
        return array_to_sort

if __name__ == '__main__':
    # main()

    arr = [4,5,7,3,2,1]
    test = my_sort(arr)
    print (test)