Skip to main content

Simplistic dependency injection container for python

Project description

This package provides a simple inversion-of-control container.

Install with

pip install pythonioc

Quick Start

The main idea is: services are registered to a service-registry and can be injected into users of that service (which can of course be services themselves).

You have two options:

  1. use a global registry (never create a registry yourself)
  2. use a local registry

Examples are below, more details will follow.

Global Registry

import pythonioc

# register your service with a default name (here: 'someService', see Notes On Names)
class SomeService(object):

    # called when the service is auto-instantiated.
    def postInit(self):

class DifferentService(object):

# for classes which we cannot decorate:

# when we don't even have the class (or don't care about lazy-initialization)

class ServiceUser(object):
    # inject the dependency by class
    service = pythonioc.Inject(SomeService)

    # inject the dependency by name (for cyclic dependencies)
    service2 = pythonioc.Inject('DifferentNameService')

 myUser = ServiceUser()

 myUser.service # --> automatically created and injected service instance.

 # explicitly get a service

Local Registry

class Service(object):

    # this will make the service registry inject a service named "someOtherService" which
    # comes from class SomeOtherService
    _someOtherService = None

    def __init__(self):

    # will be called after everything is injected
    def postInit(self):

    # will be called right before the object is destroyed (the registry's clean
    # method is called)
    def preDestroy(self):

class SomeOtherService(object):

# let's register our services
reg = ServiceRegistry()

Once everything is registered, a service can be injected by

class WiredUser(object):


    def __init__(self, *args):

wiredUser = reg.createWired(WiredUser, 'arg1', 'arg2')

Wired objects are not automatically part of the service registry, only if added by calling reg.registerServiceInstance.

Wired objects can inject their own service registry, so they can create wired objects on the fly:

class WiredUser(object):

class UserCreator(object):

    def createUser(self):
        return self._serviceRegistry.createWired(WiredUser)

userCreator = reg.createWired(UserCreator)

# create some wired users
userA = userCreator.createUser()
userB = userCreator.createUser()

Notes on Names

Services added to the registry need a name. If no name is provided, the class’ name (or the instance’s class name) is used. The name’s first character is lowered by convention.


import pythonioc

class MyService(object):

pythonioc.registerService(MyService)            # --> name is 'myService'
pythonioc.registerServiceInstance(MyService())  # --> name is 'myService'
pythonioc.registerService(MyService, serviceName='customName') # --> name is 'customName'
pythonioc.registerServiceInstance(MyService(), serviceName='customName2')  # --> name is 'customName2'

Notes on Dependency Cycles

Generally, dependency cycles are resolved by lazily initializing services. Critical cycles can still occur, when two services depend on each other within their postInit-methods that are executed after initialization. Those cycles are detected by keeping track of the currently running postInit methods and throwing an exception.

The service creation is thread safe, so accessing a non-initialized service with a long-running init or postInit method from two different threads will block one of the threads.


Bug reports, suggestions for improvements etc. are always welcome!

Project details

Download files

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

Source Distribution

pythonioc-0.4.1.tar.gz (10.5 kB view hashes)

Uploaded source

Supported by

AWS AWS Cloud computing Datadog Datadog Monitoring Facebook / Instagram Facebook / Instagram PSF Sponsor Fastly Fastly CDN Google Google Object Storage and Download Analytics Huawei Huawei PSF Sponsor Microsoft Microsoft PSF Sponsor NVIDIA NVIDIA PSF Sponsor Pingdom Pingdom Monitoring Salesforce Salesforce PSF Sponsor Sentry Sentry Error logging StatusPage StatusPage Status page