Python 3 Try Except Error Handling With Missing Arguments in Function-CodePudding

I am having trouble dealing with exceptions where the incorrect number of arguments are given when a function is called.

Here's a simplified example:

def func(arg1, arg2):
    return arg1   arg2

func(46)

When the function is called without the correct number of arguments, the following error message is generated:

TypeError: func() missing 1 required positional argument: 'arg2'

I have tried to add a try, except to handle this exception, as follows, but it does not work:

def func(arg1, arg2):
    try:
        return arg1   arg2
    except:
        return 'Incorrect input'

The function still generates the error message, rather than the 'Incorrect input' statement.

How can I have the function return the message 'Incorrect input' when the wrong number of arguments are given when the function is called?

Thanks

CodePudding user response：

The exception happens upon the function call, before entering func so you did not manage to catch it:

def func(arg1, arg2):
        return arg1   arg2

try:
    func(46)
except TypeError:
    print('Incorrect input')

Note the error message you received state it is 'TypeError' so you should catch only this kind of error.

CodePudding user response：

you can create your own try-except like below:

class IncorrectInput(Exception):
    def __init__(self, msg):
        self.msg = msg
    def __str__(self):
        return repr(self.msg)

def func(arg1, arg2 = 0):
    try:
        if type(arg1)!= int or type(arg2)!= int:
            raise IncorrectInput("Incorrect input")
        return arg1   arg2 
    except IncorrectInput as e:
        print(e)
    
    
func('a', 'b')

output:

'Incorrect input'

if you can use if-else instead of try-except. you can try this:

def func(arg1, arg2 = 0):
    if isinstance(arg1, int) and isinstance(arg1, int):
        return arg1   arg2
    else:
        return 'Incorrect input'