Question

    def n():
        name = input('What is the missing animal?')
        if name == 'dog':
                print('Well done')
        else:
         print('Sorry this is not right')
         rep= 0 
         while rep < 5:
                  n()
         rep = rep + 1
         if rep == 5:
              print ('You have guessed incorrectly 5 times.)

当我运行此程序并得到错误的答案时，程序会不断重复，而不是重复最多5次。

有什么想法吗？

Answer 1

多么尴尬的递归。：）

问题是rep变量是本地范围的，即没有传递给递归调用。

您应该将while放在外面并使用success变量和while来测试是否需要重新循环。

不需要递归。

编辑：像这样：

def n():
    rep= 0 
    success = 0
    while rep < 5 or success == 1:
        name = input('What is the missing animal?')
        if name == 'dog':
            success = 1
        else:
            print('Sorry this is not right')
            rep = rep + 1
    if rep == 5:
        print ('You have guessed incorrectly 5 times.')
    elif success == 1:
        print('Well done')

抱歉缩进。

Answer 2

def n():
    for rep in range(5):
        name = input('What is the missing animal?')
        if name == 'dog':
            print('Well done')
            break
        else:
            print('Sorry this is not right')
    else:
        print ('You have guessed incorrectly 5 times.')

由于您知道要循环多少次，（或许）更合适。 for 循环的 else 子句处理完成但没有得到正确答案的情况。

Answer 3

你一直在else语句中反复调用n（）方法。我相信这段代码可以满足您的需求：

def n():
    rep= 0
    while rep < 5:
        name = input('What is the missing animal? ')
        if name == 'dog':
            print('Well done')
            break
        else:
            print('Sorry this is not right')
        rep = rep + 1
    if rep >= 5:
        print ('You have guessed incorrectly 5 times.')

这将循环运行5次，除非您得到正确的答案。如果答案是正确的，循环将break，意味着它停止运行。最后，它检查rep是否大于（它永远不会）或等于（在第5个循环中发生）并且如果它已经循环5次则打印结束消息。

Answer 4

这是递归的正确方法。虽然这是尾递归的，所以我会把它打开到像@Prune这样的循环中。

def n(rep=0):
    if n >= 5:
        print ('You have guessed incorrectly 5 times.')
    else:
        name = input('What is the missing animal?')
        if name == 'dog':
            print('Well done')
        else:
            n(rep+1)

为什么while循环在if循环中不起作用？

4 个答案: