python 2.7.3 while循環

Question

我是python的新手。 我需要反復循環，要求用戶選擇一個選項，然后運行命令並重復直到用戶選擇退出。 如果用戶選擇任何其他選項，程序必須一直要求他們選擇一個值，直到他們選擇一個正確的值。 到目前為止，我的計划進展不順利。 如果可能的話，我想保持原狀，如果，elif條件。 有人能夠提供幫助嗎？ 非常感謝！

print """
How do you feel today?
1 = happy
2 = average
3 = sad
0 = exit program
"""

option = input("Please select one of the above options: ")
while option > 0 or option <=3:
    if option > 3:
        print "Please try again"
    elif option == 1:
        print "happy"
    elif option == 2:
        print "average"
    elif option == 3:
        print "sad"
    else:
        print "done"

Answer 1

break命令將為您退出循環 - 但是，就開始控制流而言，它也不是真正推薦的。 但請注意，用戶永遠不能輸入新值，因此您將陷入無限循環。

也許嘗試這個：

running = True

while running:
    option = input("Please select one of the above options: ")
    if option > 3:
        print "Please try again"
    elif option == 1:
        print "happy"
    elif option == 2:
        print "average"
    elif option == 3:
        print "sad"
    else:
        print "done"
        running = False

Answer 2

這是我將如何修改它以實現預期的結果。你在哪里關閉但if和else不應該在循環內:)。

print """
How do you feel today?
1 = happy
2 = average
3 = sad
0 = exit program
"""

option = input("Please select one of the above options: ")
while option >3:
    print "Please try again"
    option = input("Please select one of the above options: ")

if option == 1:
    print "happy"
elif option == 2:
    print "average"
elif option == 3:
    print "sad"
else:
    print "done"

請注意，您可以隨時使用break來停止循環

謝謝Ben

Answer 3

import sys
option = int(input("Please select one of the above options: "))
while not option in (0, 1, 2, 3):
    option = int(input("Please select one of the above options: ")
    if option == 0: sys.exit()
    else: print "Please try again"
if option == 1:
        print "happy"
elif option == 2:
        print "average"
elif option == 3:
        print "sad"

邏輯是如果選項不是0,1,2或3，程序會不斷要求輸入。 如果它在該范圍內，則循環結束並打印結果。 如果輸入為0，則程序使用sys.exit()結束。

或者，您可以使用字典創建更簡單，更短的程序：

import sys
userOptions = {1: 'happy', 2: 'average', 3: 'sad'}
option = int(input("Please select one of the above options: "))
while not option in (0, 1, 2, 3):
    option = int(input("Please select one of the above options: ")
    if option == 0: sys.exit()
    else: print "Please try again"
print userOptions[option]