prd

Idiomatic implementation of a Python function that calculates the product of the items from an iterable.

Purpose

A built-in product function that would complement the sum function was rejected, and the built-in math.sum function does not accept iterables that contain values of non-numeric types. This library exports an idiomatic implementation (using functools.reduce) of a product function that can operate on iterables that contain objects of any type for which the multiplication operation is defined (e.g., via a definition of the __mul__ method).

Installation and Usage

This library is available as a package on PyPI:

python -m pip install prd

The library can be imported in the usual ways:

import prd
from prd import prd

Examples

This library exports an idiomatic implementation of a product function (an analog of -- and complement to -- the built-in sum function). This function applies the built-in multiplication operator operator.mul to all of the items from the supplied iterable:

>>> prd([1, 2, 3, 4])
24
>>> prd([2])
2
>>> prd([1.2, 3.4, 5.6])
22.848
>>> prd([])
1

The function is compatible with objects for which the built-in multiplication operator is defined:

>>> class var(str):
...     def __mul__(self, other):
...         return self + ' * ' + other
...     def __rmul__(self, other):
...         return other + ' * ' + self
>>> prd([var('b'), var('c'), var('d')], var('a'))
'a * b * c * d'

The start parameter and the elements found in the iterable can be of different types. It is only required that the output of the multiplication operation can by multiplied with the next element from the iterable:

>>> prd([], 'a')
'a'
>>> prd([1, 2, 3], 'a')
'aaaaaa'
>>> prd(['a', 3], 2)
'aaaaaa'

Development

All installation and development dependencies are fully specified in pyproject.toml. The project.optional-dependencies object is used to specify optional requirements for various development tasks. This makes it possible to specify additional options (such as docs, lint, and so on) when performing installation using pip:

python -m pip install .[docs,lint]

Documentation

The documentation can be generated automatically from the source files using Sphinx:

python -m pip install .[docs]
cd docs
sphinx-apidoc -f -E --templatedir=_templates -o _source .. && make html

Testing and Conventions

All unit tests are executed and their coverage is measured when using pytest (see the pyproject.toml file for configuration details):

python -m pip install .[test]
python -m pytest

Alternatively, all unit tests are included in the module itself and can be executed using doctest:

python src/prd/prd.py -v

Style conventions are enforced using Pylint:

python -m pip install .[lint]
python -m pylint src/prd

Contributions

In order to contribute to the source code, open an issue or submit a pull request on the GitHub page for this library.

Versioning

The version number format for this library and the changes to the library associated with version number increments conform with Semantic Versioning 2.0.0.

Publishing

This library can be published as a package on PyPI by a package maintainer. First, install the dependencies required for packaging and publishing:

python -m pip install .[publish]

Ensure that the correct version number appears in pyproject.toml, and that any links in this README document to the Read the Docs documentation of this package (or its dependencies) have appropriate version numbers. Also ensure that the Read the Docs project for this library has an automation rule that activates and sets as the default all tagged versions. Create and push a tag for this version (replacing ?.?.? with the version number):

git tag ?.?.?
git push origin ?.?.?

Remove any old build/distribution files. Then, package the source into a distribution archive:

rm -rf build dist src/*.egg-info
python -m build --sdist --wheel .

Finally, upload the package distribution archive to PyPI:

python -m twine upload dist/*