Python 2.7.5，無限用戶輸入循環，積累總數，應用哨兵？

Question

剛剛開始使用較舊的Python書籍，瞭解循環並嘗試創建一個累積用戶輸入的循環，然後顯示總計。問題是這本書只顯示瞭如何使用範圍做到這一點，我想讓用戶輸入任意數量的數字，然後顯示總數，例如，如果用戶輸入了1,2,3,4，我會需要python輸出10，但我不想讓python綁定到一系列數字。 這裏是我有一個範圍的代碼，正如我上面所述，我需要做這個用戶輸入，而不是被束縛在一個範圍內。我是否也需要爲我想要製作的節目申請一個哨兵？

def main(): 

    total = 0.0 

    print ' this is the accumulator test run ' 
    for counter in range(5): #I want the user to be able to enter as many numbers 
     number = input('enter a number: ') #as they want. 
     total = total + number 
    print ' the total is', total 

main() 

Answer 1

這裏您需要while-loop：

def main(): 
    total = 0.0 
    print ' this is the accumulator test run ' 
    # Loop continuously. 
    while True: 
     # Get the input using raw_input because you are on Python 2.7. 
     number = raw_input('enter a number: ') 
     # If the user typed in "done"... 
     if number == 'done': 
      # ...break the loop. 
      break 
     # Else, try to add the number to the total. 
     try: 
      # This is the same as total = total + float(number) 
      total += float(number) 
     # But if it can't (meaning input was not valid)... 
     except ValueError: 
      # ...continue the loop. 
      # You can actually do anything in here. I just chose to continue. 
      continue 
    print ' the total is', total 
main() 

Answer 2

使用相同的邏輯，只用while循環代替它。退出循環，當用戶鍵入0

def main(): 
    total = 0 
    print 'this is the accumulator test run ' 
    while True: 
     number = input('enter a number: ') 
     if number == 0: 
      break 
     total += number 
    print 'the total is', total 

main() 

---

只是爲了好玩，這裏是一個在線解決方案：

total = sum(iter(lambda: input('Enter number (or 0 to finish): '), 0)) 

如果你想讓它馬上顯示：

print sum(iter(lambda: input('Enter number (or 0 to finish): '), 0)) 

Answer 3

使用while循環循環的次數不定數：

total = 0.0 
print 'this is the accumulator test run ' 
while True: 
    try: 
     # get a string, attempt to cast to float, and add to total 
     total += float(raw_input('enter a number: ')) 
    except ValueError: 
     # raw_input() could not be converted to float, so break out of loop 
     break 
print 'the total is', total 

測試運行：

this is the accumulator test run 
enter a number: 12 
enter a number: 18.5 
enter a number: 3.3333333333333 
enter a number: 
the total is 33.8333333333