如何防止循環中的布爾值無限循環？

Question

我有一些代碼是這樣：

maybeYes = raw_input("Please enter Yes to continue.") 
    if maybeYes != "Yes": 
     print "Try again." 
     # ask for input again 
    else: 
     pass 

我填，我希望把它再次要求輸入什麼？

Answer 1

你應該直接在循環中執行raw_input。

while True: 
    result = raw_input("...") 
    if result != "Yes": 
     print "Try again." 
     continue 
    else: 
     break 

Answer 2

它在我看來像你想在這裏一個無限循環。

maybeYes = raw_input("Please enter Yes to continue.") 
while maybeYes != "Yes": 
    maybeYes = raw_input("Please try again.") 

但是，您可以隨時添加計數器/轉義。

maybeYes = raw_input("Please enter Yes to continue.") 
attempts = 0 
while maybeYes != "Yes" and attempts < 10: 
    maybeYes = raw_input("Please try again.") 
    attempts += 1 

Answer 3

這將循環打印wrong直到用戶類型yes，Yes，YEs，YES，yEs或yeS作爲輸入對YES檢查之前轉換爲大寫，那麼你的代碼就可以繼續...

while raw_input("Please enter Yes to start: ").upper() != 'YES': 
     print 'Wrong' 

print 'Correct' 

#Carry on here 

輸出：

Please enter Yes to start: nowg 
Wrong 
Please enter Yes to start: wggwe 
Wrong 
Please enter Yes to start: Yes 
Correct