Skip to main content

Tiny util for creating tensorflow-like context managers for default instances of classes

Project description

https://badge.fury.io/py/defaultcontext.svg https://travis-ci.org/bogdan-kulynych/defaultcontext.svg?branch=master

Tiny util for creating tensorflow-like context managers for default instances of classes.

Installation

You can install defaultcontext using pip:

pip install defaultcontext

Usage

The library provides the with_default_context class decorator which simply does two things:

  • Adds static method Class.get_default() which returns the default object in the current context block.

  • Adds method instance.as_default() to the class, which manages a context within which the instance becomes default

This is useful for creating psuedo-global objects that can be accessed from any code executed within a given context block without passing such objects around.

This idea is inspired by Graph and Session classes from Google’s tensorflow.

Basic usage:

from defaultcontext import with_default_context


@with_default_context
class Environment:
    def __init__(self, name):
        self.name = name

    def __str__(self):
        return 'Environment %s' % self.name


with Environment(name='A').as_default():
    print(Environment.get_default())      # A

with Environment(name='B').as_default():
    print(Environment.get_default())      # B

print(Environment.get_default())          # None

If with_default_context was called without parameters the global default value of a class will be None. The global default can be added using global_default_factory:

def make_default_env():
    return Environment(name='default')

@with_default_context(global_default_factory=make_default_env)
class Environment:
    def __init__(self, name):
        self.name = name

    def __str__(self):
        return self.name

Environment.get_default()                      # default

with Environment(name='custom').as_default():
    print(Environment.get_default())           # custom

Environment.get_default()                      # default

Alternatively, if the class can be constructed without arguments, global default can be set to Class() by setting use_empty_init to True:

@with_default_context(use_empty_init=True)
class Environment:
    def __init__(self, name='default'):
        self.name = name

    def __str__(self):
        return self.name

Environment.get_default()                      # default

with Environment(name='custom').as_default():
    print(Environment.get_default())           # custom

Environment.get_default()                      # default

Download files

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

Source Distribution

defaultcontext-1.1.0.tar.gz (8.4 kB view hashes)

Uploaded Source

Built Distribution

defaultcontext-1.1.0-py2.py3-none-any.whl (10.0 kB view hashes)

Uploaded Python 2 Python 3

Supported by

AWS AWS Cloud computing and Security Sponsor Datadog Datadog Monitoring Fastly Fastly CDN Google Google Download Analytics Microsoft Microsoft PSF Sponsor Pingdom Pingdom Monitoring Sentry Sentry Error logging StatusPage StatusPage Status page