试图让我的代码只输入数字值，如果它输入一个非数字值，它会打印你输入了一个非数字值，但它不起作用答案

【问题标题】：Trying to get my code to input only digit values and if it inputs a non digit value it prints You have input a non digit value but its not working试图让我的代码只输入数字值，如果它输入一个非数字值，它会打印你输入了一个非数字值，但它不起作用
【发布时间】：2022-01-02 23:02:24
【问题描述】：

它似乎只将小数识别为非数字值，但如果我戴上写一个单词，它会说无法将字符串转换为浮点数-我该如何解决这个问题，我是编程新手

【问题讨论】：

您应该阅读try 和except 作为捕获此类错误的方法。

标签： python string if-statement while-loop

【解决方案1】：

试试这个

selection=input("Select a menu- Input a number:")
if not selection.isdigit():
    print("You have input a non digit value. Select again:")
else:
    selection = float(selection)
    if selection==1:
        print("::menu 1::")
    elif selection==2:
        print("::menu 2::")
    elif selection==3:
        print("::menu 3::")
    elif selection==4:
        exit
    elif selection<=0 or selection>4:
        print("There is no menu",end=" ")
        print(selection)

【讨论】：

【解决方案2】：

我对您的代码进行了一些更改并内联添加了一些 cmets

# We start with None so that it enters the loop at least once
selection = None


# We create loop to keep asking the question until the user provides a number
while not selection:
    selection=input("Select a menu- Input a number:")
    # Check if the number is a decimal
    if selection.isdecimal():
        # I convert to an int since it's more natural
        selection = int(selection)
        # At this point, it will exit the loop
    else:
        # The user has intereed an incorrect value. 
        print("You have input a non integer value. Select again:")
        # We empty selection so that it loops and asks the question again
        selection = None

# Here we have an int
# If the selection is 1, 2 or 3, we display the menu. I use a list, 
# but range(1, 3) would have worked too
if selection in [1, 2, 3]:
    # Note I use an f-string here. You might not have learned about
    # them yet. Requires at least Python 3.6
    # This helps avoid repetition
    print(f"::menu {selection}::")
elif selection==4:
    # always call it like a function
    exit()
else:
    # Any other selection (remember, we know we have an int) should get this message
    print(f"There is no menu {selection}")

【讨论】：

【解决方案3】：

试试这个：

while True:
    selection=input("Select a menu- Input a number:")

if not selection.isdigit():
    print("You have input a non digit value. Select again:")
else:
    selection = int(selection)
    if selection==1:
        print("::menu 1::")
    elif selection==2:
        print("::menu 2::")
    elif selection==3:
        print("::menu 3::")
    elif selection==4:
        print('Exiting...')
        quit()
    else:
        print("There is no menu",end=" ")
        print(selection)

【讨论】：