https://github.com/ekampf/pymaybe

A Python implementation of the Maybe pattern
https://github.com/ekampf/pymaybe

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A Python implementation of the Maybe pattern

• Host: GitHub
• URL: https://github.com/ekampf/pymaybe
• Owner: ekampf
• License: bsd-3-clause
• Created: 2015-07-13T06:09:07.000Z (over 9 years ago)
• Default Branch: master
• Last Pushed: 2022-12-26T19:44:22.000Z (about 2 years ago)
• Last Synced: 2024-12-28T14:11:29.498Z (9 days ago)
• Language: Python
• Size: 53.7 KB
• Stars: 208
• Watchers: 7
• Forks: 6
• Open Issues: 7
• Metadata Files:
  • Readme: README.rst
  • Changelog: HISTORY.rst
  • Contributing: CONTRIBUTING.rst
  • License: LICENSE

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README

        
===============================

PyMaybe

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A Python implementation of the Maybe pattern.

Installation

------------

.. code::

    pip install pymaybe

Getting Started

---------------

.. code::

    from pymaybe import maybe

    first_name = maybe(deep_hash)['account']['user_profile']['first_name'].or_else("")

Documentation

-------------

Maybe monad is a programming pattern that allows to treat None values that same way as non-none values.

This is done by wrapping the value, which may or may not be None to, a wrapper class.

The implementation includes two classes: *Maybe* and *Something*.

*Something* represents a value while *Nothing* represents a None value.

There's also a method *maybe* which wraps a regular value and and returns *Something* or *Nothing* instance.

.. code::

    >>> maybe("I'm a value")

    "I'm a value"

    >>> maybe(None);

    None

Both *Something* and *Nothing* implement 4 methods allowing you to test their real value: *is_some*, *is_none*, *get* and *or_else*

.. code::

    >>> maybe("I'm a value").is_some()

    True

    >>> maybe("I'm a value").is_none()

    False

    >>> maybe(None).is_some()

    False

    >>> maybe(None).is_none()

    True

    >>> maybe("I'm a value").get()

    "I'm a value"

    >>> maybe("I'm a value").or_else(lambda: "No value")

    "I'm a value"

    >>> maybe(None).get()

    Traceback (most recent call last):

    ...

    Exception: No such element

    >>> maybe(None).or_else(lambda: "value")

    'value'

    >>> maybe(None).or_else("value")

    'value'

In addition, *Something* and *Nothing* implement the Python magic methods allowing you to treat them as dictionaries:

.. code::

    >>> nested_dict = maybe(nested_dict)

    >>> nested_dict['store']['name']

    'MyStore'

    >>> nested_dict['store']['address']

    None

    >>> nested_dict['store']['address']['street'].or_else('No Address Specified')

    'No Address Specified'

All other method calls on *Something* are forwarded to its real *value*:

.. code::

    >>> maybe('VALUE').lower()

    'value'

    >>> maybe(None).invalid().method().or_else('unknwon')

    'unknwon'

Examples & Use Cases

--------------------

The Maybe pattern helps you avoid nasty try..except blocks.

Consider the following code:

.. code::

    try:

        url = rss.load_feeds()[0].url.domain

    except (TypeError, IndexError, KeyError, AttributeError):

        url = "planetpython.org"

With Maybe you could simply do:

.. code::

    url = maybe(rss).load_feeds()[0]['url'].domain.or_else("planetpython.org")

Getting the current logged in user's name.

Without maybe:

.. code::

    def get_user_zipcode():

        address = getattr(request.user, 'address', None)

        if address:

            return getattr(address, 'zipcode', '')

        return ''

With maybe:

.. code::

    def get_user_zipcode():

        return maybe(request.user).address.zipcode.or_else('')

Further Reading

---------------

* `Option (Scala) `_

* `Maybe (Java) `_

* `Maybe pattern (Python recipe) `_

* `Data.Maybe (Haskell) `_

* `Maybe (Ruby) `_

Copyright and License

---------------------

Copyright 2015 - `Eran Kampf `_

* Free software: BSD license

* Documentation: https://pymaybe.readthedocs.org.

* Code is hosted on `GitHub `_