檢測輸入是int還是str•Python 2.7

Question

**編輯：***已解決！*

編程一個程序，它會告訴你，如果你足夠大，可以投票。而且，當它詢問你的年齡時，如果用戶輸入的是字母而不是數字，我希望它能說某件事，例如「請輸入數字，而不是字母，重新啓動」。這裏是我現在所擁有的代碼：

name = raw_input("What is your name?: ") 
print("") 
print("Hello, "+name+".\n") 
print("Today we will tell you if you are old enough to vote.") 
age = input("How old are you?: ") 
if age >= 18: 
    print("You are old enough to vote, "+name+".") 
elif age < 18: 
    print("Sorry, but you are not old enough to vote, "+name+".") 

Answer 1

你可以嘗試這樣的事情：

name = raw_input("What is your name?: ") 
print("") 
print("Hello, "+name+".\n") 
print("Today we will tell you if you are old enough to vote.") 
while True: 
    try: 
     #get the input to be an integer. 
     age = int(raw_input("How old are you?: ")) 
     #if it is you break out of the while 
     break 
    except ValueError: 
     print("Please enter a number, not a letter. Restart.") 
if age >= 18: 
    print("You are old enough to vote, "+name+".") 
elif age < 18: 
    print("Sorry, but you are not old enough to vote, "+name+".") 

Answer 2

name = raw_input("What is your name?: ") 
print("") 
print("Hello, "+name+".\n") 
print("Today we will tell you if you are old enough to vote.") 
while True: 
    age = raw_input("How old are you?: ") 
    try: 
     age = int(age) 
    except ValueError: 
     print("Please enter a number, not a letter. Restart.") 
    else: 
     break 
if age >= 18: 
    print("You are old enough to vote, "+name+".") 
elif age < 18: # else: 
    print("Sorry, but you are not old enough to vote, "+name+".") 

在try-except-else，我們儘量年齡將從字符串爲整數。如果發生ValueError，則意味着輸入字符串不是合法的整數。如果沒有，那麼我們可以跳出while循環並執行以下任務。

注意1：最好不要在python2中使用input()。請參閱this。

注2：elif是沒用的。只需使用else即可。