product.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
"""
This is a module for mathematical utility functions.
"""
from __future__ import print_function  # This is for Python2

__author__ = "author"
__version__ = "1.0.0"
__copyright__ = "Copyright 2017, Planet Earth"
__license__ = "GPLv2"
__email__ = "mail@example.com"
__status__ = "Development"  # "Prototype", "Development", or "Production"

__all__ = ["product"]

from logging import getLogger, StreamHandler, Formatter
_log = getLogger(__name__)
handler = StreamHandler()
formatter = Formatter(fmt='%(levelname)s:%(name)s:%(message)s')
handler.setFormatter(formatter)
from logging import DEBUG
lv = DEBUG  # This is a log level: CRITICAL, ERROR, WARNING, INFO, or DEBUG
handler.setLevel(lv)
_log.setLevel(lv)
_log.addHandler(handler)

import functools

def product(values):
    """
    Calculate the product of given integers.

    Parameters
    ----------
    values : iterable
        A list of integers

    Returns
    -------
    res : int
        A product

    Examples
    --------
    >>> product([])
    1
    >>> product([2])
    2
    >>> product([2, 3, 4, 5])
    120

    """
    _log.info("function 'product' was called with values={}.".format(str(values)))
    res = functools.reduce(lambda a, b: a * b, values, 1)
    _log.info("a result is {:d}.".format(res))
    return res

def _main():
    import platform
    _log.info("the version is {}.".format(platform.python_version()))
    (major, minor, _) = platform.python_version_tuple()
    if major != '3':
        raise RuntimeError("The version is too old '{}'. Use Python3.".format(platform.python_version()))
    elif int(minor) < 5:
        _log.warn("the version is a bit old '{}'. Use Python3.5 or later.".format(platform.python_version()))

    import argparse
    parser = argparse.ArgumentParser(description='Process some integers.')
    parser.add_argument('integers', metavar='N', type=int, nargs='*', help='an integer for the product')
    args = parser.parse_args()

    print(product(args.integers))


if __name__ == "__main__":
    _main()  # Do nothing except for calling _main

$ python product.py --help
$ python product.py 1 2 3
$ python -m doctest -v product.py