程序沒有任何返回

Question

我看到這個Flowchart，並決定製作一個程序。問題是，如果我第一次輸入「否」，它只會返回「去外部」。所有其他人返回「無」。即時通訊使用Python 2.7

def waitawhile(): 
    print "Wait a while" 
    rain2 = raw_input("Is it still raining?") 
    if rain2.lower() == "no": 
     return "Go Outside" 
    elif rain2.lower() == "yes": 
     waitawhile() 
def Raining(): 
    print "Is it raining?" 
    rain = raw_input() 
    if rain.lower() == "no": 
     return "Go Outside" 
    elif rain.lower() == "yes": 
     print "Have Umbrella?" 
     umbrella = raw_input() 
     if umbrella.lower == "yes": 
      return "Go Outside" 
     elif umbrella.lower() == "no": 
      waitawhile() 
print Raining() 

Answer 1

問題是與您的通話waitawhile（來自Raining和waitawhile本身）。調用它之後，您將丟棄返回值並不返回任何內容。

waitawhile() 

到：要解決這個問題，呼叫從改變

return waitawhile() 

確保，兩個功能，也沒有辦法到達函數的結尾而不執行return聲明。

Answer 2

你的程序有三個問題，在它們被固定如下：

def waitawhile(): 
    print "Wait a while" 
    rain2 = raw_input("Is it still raining?") 
    if rain2.lower() == "no": 
     return "Go Outside" 
    elif rain2.lower() == "yes": 
     return waitawhile() 
def Raining(): 
    print "Is it raining?" 
    rain = raw_input() 
    if rain.lower() == "no": 
     return "Go Outside" 
    elif rain.lower() == "yes": 
     print "Have Umbrella?" 
     umbrella = raw_input() 
     if umbrella.lower() == "yes": 
      return "Go Outside" 
     elif umbrella.lower() == "no": 
      return waitawhile() 
print Raining() 

作如下處理：

>>> ================================ RESTART ================================ 
>>> 
Is it raining? 
yes 
Have Umbrella? 
yes 
Go Outside 
>>> ================================ RESTART ================================ 
>>> 
Is it raining? 
yes 
Have Umbrella? 
no 
Wait a while 
Is it still raining?yes 
Wait a while 
Is it still raining?no 
Go Outside 
>>> 

在你的程序的問題是邏輯上的錯誤，所以解釋將不顯示您出現語法錯誤：

1. 您使用.lower而不是.lower()在i f條件，它將永遠是假的。
2. 您忽略了waitawhile()方法的回報，而您必須將它們返回到print方法。