Don't try this at home, kids!

.. _faq-positional-only-arguments:

What does the slash(/) in the parameter list of a function mean?

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A slash in the argument list of a function denotes that the parameters prior to

it are positional-only. Positional-only parameters are the ones without an

externally-usable name. Upon calling a function that accepts positional-only

parameters, arguments are mapped to parameters based solely on their position.

For example, :func:`pow` is a function that accepts positional-only parameters.

Its documentation looks like this::

>>> help(pow)

Help on built-in function pow in module builtins:

pow(x, y, z=None, /)

Equivalent to x**y (with two arguments) or x**y % z (with three arguments)

Some types, such as ints, are able to use a more efficient algorithm when

invoked using the three argument form.

The slash at the end of the parameter list means that all three parameters are

positional-only. Thus, calling :func:`pow` with keyword aguments would lead to

an error::

>>> pow(x=3, y=4)

Traceback (most recent call last):

File "<stdin>", line 1, in <module>

TypeError: pow() takes no keyword arguments

Note that as of this writing this is only documentational and no valid syntax

in Python, although there is :pep:`570`, which proposes a syntax for

position-only parameters in Python.

Numbers and strings

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