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A decorator to make a function accept keyword arguments only, on both Python 2 and 3.

Project description

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A decorator to make a function accept keyword arguments only, on both Python 2 and 3.

If you are only using Python 3, you don’t need this, you can just do:

def myfunction(*, foo=1, bar=2):
    pass

Why?

If you are making a library (that still supports Python 2), you might want to make all functions in its API take keyword arguments only, for a couple of reasons:

  • To avoid user confusion, e.g. if you take x and y arguments as coordinates, it’s easy to forget which way round to pass them.

  • To make your API easier to extend - you’ll know no callers rely on the positional argument ordering, so can refactor this to make sense.

Installation

Use pip:

pip install kwargs-only

Tested on Python 2.7 and Python 3.6.

Usage

Import the decorator and apply it to a function:

from kwargs_only import kwargs_only

@kwargs_only
def myfunction(foo=1, bar=2):
    pass

Then calling the function with positional arguments will cause it to fail with TypeError:

>>> myfunction(1, 2)
...
TypeError: myfunction should only be called with keyword args

The decorator detects methods and classmethods, by allowing for the first argument to be a positional one if its name is self or cls. kwargs_only should be applied to the function before classmethod is. For example:

class MyClass:

    @classmethod
    @kwargs_only
    def my_class_method(cls, foo=1):
        pass

    @kwargs_only
    def my_instance_method(self, bar=1):
        pass

That’s about all there is to it! Enjoy!

History

Pending Release

1.0.0 (2017-06-18)

  • First release on PyPI, featuring kwargs_only decorator.

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