https://github.com/ivankorobkov/python-inject
Python dependency injection
https://github.com/ivankorobkov/python-inject
Last synced: 16 days ago
JSON representation
Python dependency injection
- Host: GitHub
- URL: https://github.com/ivankorobkov/python-inject
- Owner: ivankorobkov
- License: apache-2.0
- Created: 2010-02-08T06:46:16.000Z (over 15 years ago)
- Default Branch: master
- Last Pushed: 2024-11-29T10:39:23.000Z (11 months ago)
- Last Synced: 2025-03-03T19:40:45.381Z (8 months ago)
- Language: Python
- Homepage:
- Size: 463 KB
- Stars: 716
- Watchers: 18
- Forks: 81
- Open Issues: 23
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGES.md
- License: LICENSE
Awesome Lists containing this project
- awesome-dependency-injection-in-python - Inject - Python dependency injection. [🐍, Apache License 2.0]. (Software / DI Frameworks / Containers)
- awesome-starts - ivankorobkov/python-inject - Python dependency injection (Python)
README
# python-inject [](https://travis-ci.org/ivankorobkov/python-inject)
Dependency injection the python way, the good way.
## Key features
* Fast.
* Thread-safe.
* Simple to use.
* Does not steal class constructors.
* Does not try to manage your application object graph.
* Transparently integrates into tests.
* Autoparams leveraging type annotations.
* Supports type hinting in Python 3.5+.
* Supports Python 3.9+ (`v5.*`), 3.5-3.8 (`v4.*`) and Python 2.7–3.5 (`v3.*`).
* Supports context managers.
## Python Support
| Python | Inject Version |
|---------|----------------|
| 3.9+ | 5.0+ |
| 3.6-3.8 | 4.1+, < 5.0 |
| 3.5 | 4.0 |
| < 3.5 | 3.* |
## Installation
Use pip to install the lastest version:
```bash
pip install inject
```
## Autoparams example
`@inject.autoparams` returns a decorator which automatically injects arguments into a function
that uses type annotations. This is supported only in Python >= 3.5.
```python
@inject.autoparams
def refresh_cache(cache: RedisCache, db: DbInterface):
pass
```
There is an option to specify which arguments we want to inject without attempts of
injecting everything:
```python
@inject.autoparams('cache', 'db')
def sign_up(name, email, cache: RedisCache, db: DbInterface):
pass
```
It is also acceptable to use explicit curly braces notation (`@inject.autoparams()`)
for non-parameterized decorations — it will be treated the same as `@inject.autoparams`.
## Step-by-step example
```python
# Import the inject module.
import inject
# `inject.instance` requests dependencies from the injector.
def foo(bar):
cache = inject.instance(Cache)
cache.save('bar', bar)
# `inject.params` injects dependencies as keyword arguments or positional argument.
# Also you can use @inject.autoparams in Python 3.5, see the example above.
@inject.params(cache=Cache, user=CurrentUser)
def baz(foo, cache=None, user=None):
cache.save('foo', foo, user)
# this can be called in different ways:
# with injected arguments
baz('foo')
# with positional arguments
baz('foo', my_cache)
# with keyword arguments
baz('foo', my_cache, user=current_user)
# `inject.param` is deprecated, use `inject.params` instead.
@inject.param('cache', Cache)
def bar(foo, cache=None):
cache.save('foo', foo)
# `inject.attr` creates properties (descriptors) which request dependencies on access.
class User(object):
cache = inject.attr(Cache)
def __init__(self, id):
self.id = id
def save(self):
self.cache.save('users', self)
@classmethod
def load(cls, id):
return cls.cache.load('users', id)
# Create an optional configuration.
def my_config(binder):
binder.bind(Cache, RedisCache('localhost:1234'))
# Configure a shared injector.
inject.configure(my_config)
# Instantiate User as a normal class. Its `cache` dependency is injected when accessed.
user = User(10)
user.save()
# Call the functions, the dependencies are automatically injected.
foo('Hello')
bar('world')
```
## Context managers
Binding a class to an instance of a context manager (through `bind` or `bind_to_constructor`)
or to a function decorated as a context manager leads to the context manager to be used as is,
not via with statement.
```python
@contextlib.contextmanager
def get_file_sync():
obj = MockFile()
yield obj
obj.destroy()
@contextlib.asynccontextmanager
async def get_conn_async():
obj = MockConnection()
yield obj
obj.destroy()
def config(binder):
binder.bind_to_provider(MockFile, get_file_sync)
binder.bind(int, 100)
binder.bind_to_provider(str, lambda: "Hello")
binder.bind_to_provider(MockConnection, get_conn_sync)
inject.configure(config)
@inject.autoparams()
def example(conn: MockConnection, file: MockFile):
# Connection and file will be automatically destroyed on exit.
pass
```
## Usage with Django
Django can load some modules multiple times which can lead to
`InjectorException: Injector is already configured`. You can use `configure(once=True)` which
is guaranteed to run only once when the injector is absent:
```python
import inject
inject.configure(my_config, once=True)
```
## Testing
In tests use `inject.configure(callable, clear=True)` to create a new injector on setup,
and optionally `inject.clear()` to clean up on tear down:
```python
class MyTest(unittest.TestCase):
def setUp(self):
inject.configure(lambda binder: binder
.bind(Cache, MockCache()) \
.bind(Validator, TestValidator()),
clear=True)
def tearDown(self):
inject.clear()
```
## Composable configurations
You can reuse configurations and override already registered dependencies to fit the needs
in different environments or specific tests.
```python
def base_config(binder):
# ... more dependencies registered here
binder.bind(Validator, RealValidator())
binder.bind(Cache, RedisCache('localhost:1234'))
def tests_config(binder):
# reuse existing configuration
binder.install(base_config)
# override only certain dependencies
binder.bind(Validator, TestValidator())
binder.bind(Cache, MockCache())
inject.configure(tests_config, allow_override=True, clear=True)
```
## Thread-safety
After configuration the injector is thread-safe and can be safely reused by multiple threads.
## Binding types
**Instance** bindings always return the same instance:
```python
redis = RedisCache(address='localhost:1234')
def config(binder):
binder.bind(Cache, redis)
```
**Constructor** bindings create a singleton on injection:
```python
def config(binder):
# Creates a redis cache singleton on first injection.
binder.bind_to_constructor(Cache, lambda: RedisCache(address='localhost:1234'))
```
**Provider** bindings call the provider on injection:
```python
def get_my_thread_local_cache():
pass
def config(binder):
# Executes the provider on each injection.
binder.bind_to_provider(Cache, get_my_thread_local_cache)
```
**Runtime** bindings automatically create singletons on injection, require no configuration.
For example, only the `Config` class binding is present, other bindings are runtime:
```python
class Config(object):
pass
class Cache(object):
config = inject.attr(Config)
class Db(object):
config = inject.attr(Config)
class User(object):
cache = inject.attr(Cache)
db = inject.attr(Db)
@classmethod
def load(cls, user_id):
return cls.cache.load('users', user_id) or cls.db.load('users', user_id)
inject.configure(lambda binder: binder.bind(Config, load_config_file()))
user = User.load(10)
```
## Disabling runtime binding
Sometimes runtime binding leads to unexpected behaviour. Say if you forget
to bind an instance to a class, `inject` will try to implicitly instantiate it.
If an instance is unintentionally created with default arguments it may lead to
hard-to-debug bugs. To disable runtime binding and make sure that only
explicitly bound instances are injected, pass `bind_in_runtime=False` to `inject.configure`.
In this case `inject` immediately raises `InjectorException` when the code
tries to get an unbound instance.
## Keys
It is possible to use any hashable object as a binding key. For example:
```python
import inject
inject.configure(lambda binder: \
binder.bind('host', 'localhost') \
binder.bind('port', 1234))
```
## Why no scopes?
I've used Guice and Spring in Java for a lot of years, and I don't like their scopes.
`python-inject` by default creates objects as singletons. It does not need a prototype scope
as in Spring or NO_SCOPE as in Guice because `python-inject` does not steal your class
constructors. Create instances the way you like and then inject dependencies into them.
Other scopes such as a request scope or a session scope are fragile, introduce high coupling,
and are difficult to test. In `python-inject` write custom providers which can be thread-local,
request-local, etc.
For example, a thread-local current user provider:
```python
import inject
import threading
# Given a user class.
class User(object):
pass
# Create a thread-local current user storage.
_LOCAL = threading.local()
def get_current_user():
return getattr(_LOCAL, 'user', None)
def set_current_user(user):
_LOCAL.user = user
# Bind User to a custom provider.
inject.configure(lambda binder: binder.bind_to_provider(User, get_current_user))
# Inject the current user.
@inject.params(user=User)
def foo(user):
pass
```
## Links
* Project: https://github.com/ivankorobkov/python-inject
## License
Apache License 2.0
## Contributors
* Ivan Korobkov [@ivankorobkov](https://github.com/ivankorobkov)
* Jaime Wyant [@jaimewyant](https://github.com/jaimewyant)
* Sebastian Buczyński [@Enforcer](https://github.com/Enforcer)
* Oleksandr Fedorov [@Fedorof](https://github.com/Fedorof)
* cselvaraj [@cselvaraj](https://github.com/cselvaraj)
* 陆雨晴 [@SixExtreme](https://github.com/SixExtreme)
* Andrew William Borba [@andrewborba10](https://github.com/andrewborba10)
* jdmeyer3 [@jdmeyer3](https://github.com/jdmeyer3)
* Alex Grover [@ajgrover](https://github.com/ajgrover)
* Harro van der Kroft [@wisepotato](https://github.com/wisepotato)
* Samiur Rahman [@samiur](https://github.com/samiur)
* 45deg [@45deg](https://github.com/45deg)
* Alexander Nicholas Costas [@ancostas](https://github.com/ancostas)
* Dmitry Balabka [@dbalabka](https://github.com/dbalabka)
* Dima Burmistrov [@pyctrl](https://github.com/pyctrl)