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!

Alternatives api is just a syntax sugar for selecting alternative variants from some set of values

Project Description

Alternatives api

Alternatives basics

Alternatives api is just a syntax sugar for selecting alternative variants from some set of values.
The main thing is alternative class that implements late call on callbacks.
This allow to apply boolean logic on callbacks without being executed::

a1 = Alternative(lambda: a)
b1 = Alternative(lambda: b)

a_b = a1 | b1
assert isinstance(a_b, Alternative)
assert bool(a_b) is (a or b)

Also you can note, in the example above, that alternative can provide python truth when it's needed by
calling callbacks and evaluating boolean expressions.

Alternatives usage

How it may be used::

os_centos() or os_windows(): 'php',
os_ubuntu(): 'php5'

Here one of values will be selected: php or php5.

Alternative is object, that's why we can use it as dictionary key.

In the example above you can see one_of() method:

.. automodule:: pywizard.api
:members: one_of

Another style of evaluating alternatives is all_of:

.. automodule:: pywizard.api
:members: all_of

And nobody restrict you from creating your own alternatives selection style.
Use source of one_of, all_of as reference.

Checks declaration

*Check* is just a python function that return boolen with added annotation on it::

def os_linux():
Checks if it is linux-like os.
info = os_info()
return 'linux' in info['platform']

.. note::
As function is annotated there is some extra work needed to provide correct documentation for this function.
@alternative handles copying __doc__ transparently for your function. But, you should take care
of specifying correct method signature in first line of docstring.

Release History

This version
History Node


Download Files

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

File Name & Hash SHA256 Hash Help Version File Type Upload Date
(5.0 kB) Copy SHA256 Hash SHA256
Source Dec 6, 2013

Supported By

WebFaction WebFaction Technical Writing Elastic Elastic Search Pingdom Pingdom Monitoring Dyn Dyn DNS Sentry Sentry Error Logging CloudAMQP CloudAMQP RabbitMQ Heroku Heroku PaaS Kabu Creative Kabu Creative UX & Design Fastly Fastly CDN DigiCert DigiCert EV Certificate Rackspace Rackspace Cloud Servers DreamHost DreamHost Log Hosting