Python function with many optional arguments

Question

I currently have a function with many optional arguments, something like this:

def many_argument_function(required1, required2, optional1=1, optional2=2,
                           optional3=None, optional4="Test", optional5="g",
                           optional6=2, optional7=(0, 255, 0), optional8=0.5):
                           # Do stuff

But in reality, it has over 20 optional arguments which take five lines even with 120 character line limit.

Is there a design pattern to simplify this/make it prettier?

P.S. I have considered making a separate configuration file for this function, but then calling it would be annoying since most of the time only one or two optional arguments are used.

EDIT1: I don't want to use kwargs as I want names of arguments and default values visible in my IDE (PyCharm)

Possible duplicate of Is there a way to pass optional parameters to a function? — stovfl
– stovfl, Commented Sep 24, 2018 at 16:31
I don't want to use kwargs as I want names and default values visible in IDE — Rizhiy
– Rizhiy, Commented Sep 24, 2018 at 16:34
couldn't you put your optionals into a list and pass the list — vash_the_stampede
– vash_the_stampede, Commented Sep 24, 2018 at 16:35
@vash_the_stampede In python if you have a list as a default for an argument it is mutable, so can't do that. — Rizhiy
– Rizhiy, Commented Sep 24, 2018 at 16:37
No i'm saying don use a default and just pass a list containing all the default variables, if you have changes you can make a list copy with the change, and pass that — vash_the_stampede
– vash_the_stampede, Commented Sep 24, 2018 at 16:38

chepner · Accepted Answer · 2018-09-24 16:59:54Z

There's nothing wrong with just listing one parameter per line.

def many_argument_function(
        required1,
        required2,
        optional1=1,
        optional2=2,
        optional3=None,
        optional4="Test",
        optional5="g",
        optional6=2,
        optional7=(0, 255, 0),
        optional8=0.5
    ):

    """
    This function does some stuff.
    """

    # Do stuff

PEP 8 endorses this style of indentation, and although its own example puts multiple parameters on a single line, I find it much easier to scan a large list of parameters if each is on its own line.

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