Python的NameError：名字「北」不是文字遊戲

Question

定義我爲我的基於文本的遊戲的代碼和我收到一個錯誤說

line 1, in <module> 
userInput = input("Please enter a direction in which to travel: ") 
File "<string>", line 1, in <module> 
NameError: name 'north' is not defined 

這裏是我的代碼

userInput = input("Please enter a direction in which to travel: ") 
Map = { 
    'north':'that way leads to the kitchen', 
    'south':'that way leads to the dining room', 
    'east':'that way leads to the entry', 
    'west':'that way leads to the living room' 
} 
if userInput == north: 
    print Map['north'] 
elif userInput == south: 
    print Map['south'] 
elif userInput == east: 
    print Map['east'] 
elif userInput == West: 
    print Map['west'] 
elif userInput == '': 
    print "Please specify a various direction." 
else: 
    quit 

感謝您的幫助

Answer 1

當使用Python 2時，您應始終使用raw_input()來獲取來自用戶的輸入。

input()相當於eval(raw_input());因此，你的代碼試圖找到一個名爲「北」，當你鍵入它的變量。

然而，在Python 3，input()的作用一樣raw_input()做在Python 2

---

你也應該將您的輸入與字符串進行比較，而不是您創建的變量。例如，if userInput == north應該是if userInput == 'north'。這使得'north'成爲一個字符串。

你可以只總結一下你的代碼：

print Map.get(userInput, 'Please specify a various direction') 

Answer 2

此行

if userInput == north: 
    ... 

是要求命名userInput變量是否是一樣的變量north。

但是您尚未定義名爲north的變量。該行應該與這樣的字符串'north'進行比較。

if userInput == 'north': 
    ... 

但是，您可以在像這樣的字典鍵中測試用戶輸入。我已將你的常數改爲全部大寫。

MAP = { 
    'north':'that way leads to the kitchen', 
    'south':'that way leads to the dining room', 
    'east':'that way leads to the entry', 
    'west':'that way leads to the living room' 
} 
userInput = raw_input("Please enter a direction in which to travel: ") 
if userInput in MAP.keys(): 
    print MAP[userInput] 

此外，正如在另一個答案中提到的，raw_input比輸入更安全。

另一種方法是像這樣捕獲KeyError。

MAP = { 
    'north':'that way leads to the kitchen', 
    'south':'that way leads to the dining room', 
    'east':'that way leads to the entry', 
    'west':'that way leads to the living room' 
} 
userInput = raw_input("Please enter a direction in which to travel: ") 
try: 
    print MAP[userInput] 
except KeyError: 
    print 'What?' 

或重複，直到有效的輸入提供這樣的（並使其不區分大小寫）：

MAP = { 
    'north':'that way leads to the kitchen', 
    'south':'that way leads to the dining room', 
    'east':'that way leads to the entry', 
    'west':'that way leads to the living room' 
} 
while True: 
    userInput = raw_input("Please enter a direction in which to travel: ").lower() 
    try: 
     print MAP[userInput] 
     break 
    except KeyError: 
     print '%s is not an option' % userInput