Question

Sorry for the poor title. I really have no idea how to describe this to a search engine to find out how it works.

class MyClass(object):
    def __init__(self, contents=None):
        self.contents = contents

Specifically, the contents=None parameter.

I’ve been studying Python for about 2 months now, and that part semi-blows my mind. Any help or redirection to a similar, previously asked question will be very appreciated.

Answer 1

That’s a Default Argument Value for a Keyword Argument.

They’re pretty straightforward, as long as they’re not a mutable object like a list or dictionary.

Just in case it was the __init__ method throwing you off — it’s the instance method of a class that gets automatically called when the instance is created. Any arguments you pass when you call the class to create a new instance, like

myclass = MyClass(contents='the_contents')

or

myclass = MyClass('the_contents')

in your example, are passed to the __init__ method.