Skip to main content
This is a pre-production deployment of Warehouse. Changes made here affect the production instance of PyPI (
Help us improve Python packaging - Donate today!

A Python implementation of the Maybe pattern.

Project Description

A Python implementation of the Maybe pattern.


pip install pymaybe

Getting Started

from pymaybe import maybe
first_name = maybe(deep_hash)['account']['user_profile']['first_name'].or_else("<unknown>")


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.

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

>>> maybe(None);

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

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

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

>>> maybe(None).is_some()

>>> maybe(None).is_none()

>>> 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")

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

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

>>> nested_dict = maybe(nested_dict)
>>> nested_dict['store']['name']
>>> nested_dict['store']['address']
>>> 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:

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

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

Examples & Use Cases

The Maybe pattern helps you avoid nasty try..except blocks. Consider the following code:

url = rss.load_feeds()[0].url.domain
except (TypeError, IndexError, KeyError, AttributeError):
url = “”

With Maybe you could simply do:

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

Getting the current logged in user’s name. Without maybe:

def get_user_zipcode():
    address = getattr(request.user, 'address', None)
    if address:
        return getattr(address, 'zipcode', '')

    return ''

With maybe:

def get_user_zipcode():
    return maybe(request.user).address.zipcode.or_else('')


0.1.0 (2015-01-11)

  • First release on PyPI.

Release History

This version
History Node


History Node


History Node


History Node


History Node


History Node


History Node


Download Files

Download the file for your platform. If you're not sure which to choose, learn more about installing packages.

Filename, Size & Hash SHA256 Hash Help File Type Python Version Upload Date
(7.8 kB) Copy SHA256 Hash SHA256
Wheel 2.7 Sep 28, 2015
(16.7 kB) Copy SHA256 Hash SHA256
Source None Sep 28, 2015

Supported By

Elastic Elastic Search Pingdom Pingdom Monitoring Dyn Dyn DNS Sentry Sentry Error Logging CloudAMQP CloudAMQP RabbitMQ Kabu Creative Kabu Creative UX & Design Google Google Cloud Servers Fastly Fastly CDN StatusPage StatusPage Statuspage DigiCert DigiCert EV Certificate