如何在Python函数返回布尔值中使用tryexcept？

Question

我需要使用try-except来验证日期和时间的输入字符串。输入格式应为MM/DD/YYYY HH:MM:SS。如果validate函数返回false，则它无效。我尝试了无效的输入，但try-except没有按预期工作。没有打印错误消息。我的代码怎么了？如何修复它？谢谢

def validate_user_input(input_string):
    # check the input validation

    validation = True
    if input_string[2] != "/" or input_string[5] != "/":
        validation = False
    elif int(date) > 31 or int(date) < 1:
        validation = False
    elif int(month) > 12 or int(month) < 1:
        validation = False
    elif int(hour) < 0 or int(hour) > 24:
        validation = False
    elif int(minute) < 0 or int(minute) > 59:
        validation = False
    elif int(second) < 0 or int(second) > 59:
        validation = False
    return validation


input = input("Please input a date and time within the format of MM/DD/YYYY HH:MM:SS")
# get the information from the input

year = input[6:10]
month = input[0:2]
date = input[3:5]
hour = input[11:13]
minute = input[14:16]
second = input[17:19]

# try-except
try:
    validate_user_input(input) == False
    print("Your input is valid!")
except:
    print("Error: the input date and time is invalid!")

Answer 1

改用if语句。这应该比使用try和except更简单

if validate_user_input(input) == False:
    print("Your input is valid!")
else:
    print("Error: the input date and time is invalid!")

Answer 2

# try-except
try: 
    validate_user_input(input) == False
    print("Your input is valid!")
except:
    print("Error: the input date and time is invalid!")

似乎您要验证输入的日期&；输入的时间。但是这些代码行没有任何作用。它不做任何事情就检查情况，@dogman288回答：让它发生。我想建议图书馆打电话python-dateutil。在几行代码中，您可以非常轻松地进行验证，我希望这将节省您的时间。只需评论相关输出

from dateutil.parser import parse
from dateutil.parser._parser import ParserError


def validate_user_input(input_string: str):
    try:
        parse(input_string)
        print("Your input is valid!")
    except ParserError as error:
        print(error)


validate_user_input("12/31/2005 23:59:6")  # Your input is valid!
validate_user_input("13/31/2005 23:59:6")  # month must be in 1..12: 13/31/2005 23:59:6
validate_user_input("12/32/2005 23:59:6")  # day is out of range for month: 12/32/2005 23:59:6
validate_user_input("12/31/200511111 23:59:6")  # year 200511111 is out of range: 12/31/200511111 23:59:6
validate_user_input("12/31/2005 24:59:6")  # hour must be in 0..23: 12/31/2005 24:59:6
validate_user_input("12/31/2005 23:61:6")  # minute must be in 0..59: 12/31/2005 23:61:6
validate_user_input("12/31/2005 23:59:61")  # second must be in 0..59: 12/31/2005 23:59:61
validate_user_input("")  # String does not contain a date: 
validate_user_input("some_string")  # Unknown string format: some_string

Answer 3

except仅当一个异常被抛出而未被较早的try-except捕获时，才会捕获该异常。代码中没有raise任何内容，因此except块永远不会运行。当validate_user_input函数返回False时，您应该抛出一个错误，可能是ValueError：

try:
    if not validate_user_input(input):
        raise ValueError("Bad input")
except:
    ...