Dependency injection

>>> from diapyr import DI, types
>>>
>>> class Config: pass
>>>
>>> class Database:
...
...     @types(Config)
...     def __init__(self, config):
...         self.conninfo = config.conninfo
...
>>> class Server:
...
...     @types(Config, Database)
...     def __init__(self, config, database):
...         self.port = config.port
...         self.database = database
...
...     def serve_forever(self):
...         print(self.port)
...
>>> config = Config()
>>> config.conninfo = 'dbname=test user=postgres'
>>> config.port = 8000
>>> with DI() as di:
...     di.add(config)
...     di.add(Database)
...     di.add(Server)
...     di(Server).serve_forever()
8000