Question

I’m working on making a small Python module. I want this module to return errors, if any occur. What is the proper or standard way to create error objects in Python?

Edit: I’m not really sure how to create my own errors, surely because i am not sure how errors work (i just know how to catch them in try: ... except: ...).
So right now i made draft error messages, errors are strings. When something goes unexpected i print the and return None. I guess that’s not the proper way 🙂

Example:

    ...
    self.IsNotStringError = "Args was not a string."
    ...

def myMethod(self, args)
    """ Args must be a string. """
    if not isinstance(args, str):
       print IsNotStringError
       return None
    else:
        do things...

Edit(bis): On reading the answers below, i have looked further into Python documentation. There is a tutorial on how to make user-defined exceptions.

Example from the documentation:

class MyError(Exception):
    def __init__(self, value):
    self.value = value
    def __str__(self):
        return repr(self.value)

Answer 1

You can create your own exception class by inheriting Exception:

class YourError( Exception ): pass

next just raise it whenever you need to:

raise YourError("error message")