dic

Dependency Injection Container for Python 3+ influenced partially by Autofac. dic aims to be a tiny “out of the way” framework to help realise IoC via dependency injection. dic uses Python 3 annotations to provide hints for the components that should be injected.

Documentation

dic documentation is available via Read the Docs.

Install

dic is available via pip:

pip install dic

Features

Currently, dic supports:

1. Constructor injection for classes

2. Factory and Lazy relationships

3. Registration via:

   1. Constructor matching for a registered class

   2. Custom callback

   3. Pre-created instances

4. Lifetime scopes:

   1. Instance per dependency

   2. Single instance

Quick Example

A quick example on how to use dic:

import dic

class SimpleThing(object):
    def say(self, message):
        print(message)

class RequiresThing(object):
    def __init__(self, thing: SimpleThing):
        self.thing = thing

    def say(self, message):
        self.thing.say(message)

# build the container
builder = dic.container.ContainerBuilder()

builder.register_class(SimpleThing)
builder.register_class(RequiresThing, component_scope=dic.scope.SingleInstance)

container = builder.build()

# use the container

# Note there'll only be one of these due to SingleInstance scoping during build
x = container.resolve(RequiresThing)
x.say("my message")

Relationships

dic supports basic relationships:

1. dic.rel.Lazy - don’t create the dependency until it’s first used

2. dic.rel.Factory - the component wants to create other components. Lifetime scopes are respected. Supports custom arguments.

Using a factory:

import dic

class SimpleThing(object):
    def __init__(self, special_argument):
        self.special_argument = special_argument

class BuildsThings(object):
    def __init__(self, thing_factory: dic.rel.Factory(SimpleThing)):
        self.thing_factory = thing_factory

    def build_me_a_thing(self):
        # builds a new thing using the injected factory
        # Note that custom arguments can be provided here
        self.thing_factory(special_argument="My super special argument")

# build the container
builder = dic.container.ContainerBuilder()

builder.register_class(SimpleThing)
builder.register_class(BuildsThing)

container = builder.build()

# use the container

x = container.resolve(BuildsThing)

# use it
thing = x.build_me_a_thing()
# ...

FAQ

1. Is dic thread-safe?

Yes. dic.rel.Lazy and dic.container.Container.resolve() are thread-safe. As a result, do not store the component_context given to register_callback callbacks, as thread-safety is enforced at the container.resolve() level.

2. Can I define my own scopes?

Yes. Derive a scope from dic.scope.Scope. Scopes can be used to provide lifetime for a calling thread, for example