semvec/pypi-packages huggingface dataset:
positionalonly 0.0.3
positionnal only arguments/parameters
Requires Python: >=3.5

positionnal only arguments/parameters
=====================================

Module to fake positional only arguments (pep 497, Draft).

Let's take the following function as example:

.. code:: python

    def diff(left, right, context=3):
    '''print the diff between `left` and `right` with `context`
    '''
    ...

``right`` and ``left`` are now part of the API, and users may decide to
use ``diff(left=str1, right=str1)``, blocking api changes, so you can't
change the names of the parameters, to for example
``def diff(old, new, context=3)`` without using the C-api.

This module provide a decorator @positionalonly to make all the
default-less parameters of your function positional only, so you can
write:

::

    @positionalonly
    def diff(left, right, context=3):
    ...

Usingit like will raise a TypeError, and the function signature will use
the positional only argument syntax with the ``/`` of pep 497.

::

    >>> diff(right="bar", left="foo")
    TypeError: The following parameters of `diff` are positional only.
    They were used as keywords arguments:
    - 'right' ('bar') should be in 2nd position
    - 'left' ('foo') should be in 1st position

    >>> help(diff)
    Help on function diff in module __main__:

    diff(left, right, /, context=3)

Advanced usage
==============

By default ``positionalonly`` will make the limit between
positional-only and the rest of the arguments just before the first
argument with default. You can tweek this behavior by passing an integer
as parameter indicating the number of argument to make positional-only:

::

    >>> @positionalonly(3)
    ... def diff(old, new, context=3)
    ... pass

    >>> signature(diff)
    diff(left, right, context=3, /)


    >>> @positionalonly(1)
    ... def diff(old, new, context=3)
    ... pass

    >>> signature(diff)
    diff(left, /, right, context=3)

If you are too lazy to count, or are afraid of misscounting,
``positionalonly`` will also decide to put the limit to the first
argument which default value is ``positionalonly`` itself.

::

    >>> @positionalonly
    ... def diff(old, new, end=positionalonly, context=3)
    ... pass

    >>> signature(diff)
    diff(left, right, /, context=3)

    >>> pos_or_kw
    >>> @positionalonly
    ... def diff(old, start=pos_or_kw, context=3)
    ... pass

    >>> signature(diff)
    diff(left, /, right, context=3)

Reasons to use positional only
==============================

Naming of argument, and in particular the function signature can be
helfull for tab completion, and static analysis to understand the code.
While posistional only is usable using ``*args`` it hides all this
information both from the human and the computer.

The default behavior of Python, is to make agument by dafult, positional
an keyword.

This fact often prevent the developer from changing the name without
breaking the API.

This also prevent arbitrary ``**kwargs`` keys as they are be taken by
"positionaly or keyword" arguments.