if/elif/else 語句

Question

我的程序/項目是關於詢問用戶他是否足夠高可以乘坐過山車並提供“是”或“否”答案的陳述。 我的問題是，如果用戶輸入的不是是或否，我希望它說：“請輸入是或否。” 我的代碼一直有效，直到我嘗試插入該語句。 如何插入該語句而不會出現錯誤。

rc1 = input('Are you tall enough to ride this roller coaster? ')
if rc1 == 'no':
    print('Please exit the ride!')
elif rc1 == 'yes':
    rc2 = int(input('How tall are you? '))
if rc2 <= 119:
    print('You are not tall enough for this ride!')
else:
    print('Enter and enjoy the ride!')

Answer 1

只是一些快速的事情。 就像上面一樣，while 循環是 go 不斷提示用戶的好方法，直到您以所需格式輸入並且您的 rc2 變量在 if 語句中定義並且不可用於比較，因此需要提前定義它適用於您的第二個條件。 像這樣的東西：

rc1 = input('Are you tall enough to ride this roller coaster? ')
rc2 = 0
while str.lower(rc1) not in ('yes', 'no'):
    print('Please answer yes or no')
    rc1 = input('Are you tall enough to ride this roller coaster? ')
if rc1 == 'no':
    print('Please exit the ride!')
elif rc1 == 'yes':
    rc2 = int(input('How tall are you? '))
if rc2 <= 119:
    print('You are not tall enough for this ride!')
else:
    print('Enter and enjoy the ride!')

Answer 2

我添加了一個 while 循環，看起來如下所示：

answer = None
rc2 = None
while answer not in ("yes", "no"):
    answer = input('Are you tall enough to ride this roller coaster? ')
    if answer == "yes":
        rc2 = int(input('How tall are you? '))
    elif answer == "no":
        print('Please exit the ride!')
    else:
        print("Please enter yes or no.")
    
if rc2 <= 119:
    print('You are not tall enough for this ride!')
else:
    print('Enter and enjoy the ride!')

Answer 3

這是我的解決方案：

rc1 = input('Are you tall enough to ride this roller coaster? ')
rc2 = None
if rc1 == 'no':
    print('Please exit the ride!')
elif rc1 == 'yes':
    rc2 = int(input('How tall are you? '))
if rc2 != None:
    if rc2 <= 119:
        print('You are not tall enough for this ride!')
    else:
        print('Enter and enjoy the ride!')

或者

rc1 = input('Are you tall enough to ride this roller coaster? ')
if rc1 == 'no':
    print('Please exit the ride!')
elif rc1 == 'yes':
    rc2 = int(input('How tall are you? '))
    if rc2 <= 119:
        print('You are not tall enough for this ride!')
    else:
        print('Enter and enjoy the ride!')

您必須在開始時初始化rc2變量。 您收到錯誤的原因是程序正在檢查rc2是否小於或等於 119，而它甚至不知道變量是什么。 rc2僅在rc1等於 yes 時存在。 為了以后使用它， rc2必須存在，無論條件如何。

Answer 4

我還得到了一個快速清潔的解決方案，比我應該擁有的更多。 感謝您的幫助

rc1 = input('Are you tall enough to ride this roller coaster? ')
while rc1 not in ('yes', 'no'):
    print('Please enter yes or no.' )
    rc1 = input('Are you tall enough to ride this roller coaster? ')
if rc1 == 'no':
    print('Please exit the ride!')
elif rc1 == 'yes':
    rc2 = int(input('How tall are you? '))
    if rc2 <= 119:
        print('You are not tall enough for this ride!')
    else:
        print('Enter and enjoy the ride!')