Python: function parameter combination validation

Question

Trying to validate function parameter combinations. Such that (), (project), (project,field) and (project,field,well) are valid and every other combination (e.g. (field)) is not. If available, arguments will be strings otherwise defaults are None or empty string "". Currently doing poor man's bit mask check...

def make_thing(project=None, field=None, well=None):
    # check for valid p-f-w combinations
    check = (8 if project else 0) + (4 if field else 0) + (1 if well else 0)
    if check not in (0, 8, 8 + 4, 8 + 4 + 1):
        return None

    # continue to do work

Question: What is a proper Pythonic way to do this?

Thank you!

Arume · Accepted Answer · 2020-04-12 00:16:58Z

1

First Suggestion

def make_thing(project=None, field=None, well=None):
    if (not project and field) or (not field and well):
        return

    # continue to do work

Second Suggestion

def make_thing(project=None, field=None, well=None):
    if (bool(project), bool(field), bool(well)) not in (
        (False, False, False),
        (True, False, False),
        (True, True, False),
        (True, True, True),
    ):
        return

    # continue to do work

edited Apr 12, 2020 at 0:16

answered Apr 11, 2020 at 13:30

Arume

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3 Comments

k1m190r Over a year ago

Thank you, but this is difficult to reason about.. at least for me.

Arume Over a year ago

@k1m190r I guess so. A first suggestion may not be Pythonic. I add a second suggestion.

k1m190r Over a year ago

and to continue the craziness itertools.combinations_with_replacement([True, False], 3) ...

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