### Create Punq Container Instance

Source: https://github.com/bobthemighty/punq/blob/main/README.md

Initialize a new Punq dependency injection container. This is the entry point for managing application dependencies. The container must be explicitly created in your application's entrypoint.

```python
import punq

container = punq.Container()
```

--------------------------------

### Register Arbitrary Object with Key

Source: https://github.com/bobthemighty/punq/blob/main/README.md

Register any object instance with a string key in the container. This is the simplest registration method for storing configuration values or singleton instances that don't require instantiation.

```python
container.register("connection_string", instance="postgresql://...")
```

--------------------------------

### Register with Arguments at Registration Time

Source: https://github.com/bobthemighty/punq/blob/main/README.md

Provide constructor arguments during registration without adding them to the container. These arguments will be used whenever the service is resolved.

```python
container.register(Greeter, FileWritingGreeter, path="/tmp/foo", greeting="Hello world")
```

--------------------------------

### Register Singleton Instance

Source: https://github.com/bobthemighty/punq/blob/main/README.md

Register a specific object instance as a singleton in the container. The same instance will be returned every time the service is resolved, ensuring single instantiation.

```python
class FileWritingGreeter:
    def __init__(self, path, greeting):
        self.path = path
        self.message = greeting
        self.file = open(self.path, 'w')

    def greet(self):
        self.file.write(self.message)

one_true_greeter = FileWritingGreeter("/tmp/greetings", "Hello world")
container.register(Greeter, instance=one_true_greeter)
```

--------------------------------

### Resolve Service and Call Method

Source: https://github.com/bobthemighty/punq/blob/main/README.md

Retrieve a registered service from the container and invoke its methods. The container automatically instantiates the concrete implementation class.

```python
config = container.resolve(ConfigReader).get_config()
```

--------------------------------

### Resolve with Runtime Arguments

Source: https://github.com/bobthemighty/punq/blob/main/README.md

Resolve a service while providing additional arguments at resolution time. Arguments not provided at registration time can be supplied when resolving the dependency.

```python
container.register(Greeter, FileWritingGreeter)
greeter = container.resolve(Greeter, path="/tmp/foo", greeting="Hello world")
```

--------------------------------

### Register Service with Implementation Class

Source: https://github.com/bobthemighty/punq/blob/main/README.md

Register an abstract service class with a concrete implementation. The container will resolve requests for the service type by returning instances of the implementation class.

```python
class ConfigReader:
    def get_config(self):
        pass

class EnvironmentConfigReader(ConfigReader):
    def get_config(self):
        return {
            "logging": {
                "level": os.env.get("LOGGING_LEVEL", "debug")
            },
            "greeting": os.env.get("GREETING", "Hello world")
        }

container.register(ConfigReader, EnvironmentConfigReader)
```

--------------------------------

### Register Service with Nested Dependencies

Source: https://github.com/bobthemighty/punq/blob/main/README.md

Register a service that depends on other registered services. Punq automatically resolves and injects dependencies based on type hints in the constructor.

```python
class Greeter:
    def greet(self):
        pass

class ConsoleGreeter(Greeter):
    def __init__(self, config_reader: ConfigReader):
        self.config = config_reader.get_config()

    def greet(self):
        print(self.config['greeting'])

container.register(Greeter, ConsoleGreeter)
container.resolve(Greeter).greet()
```

--------------------------------

### Resolve Registered Object from Container

Source: https://github.com/bobthemighty/punq/blob/main/README.md

Retrieve a previously registered object from the container using its key or type. Returns the exact instance or type that was registered.

```python
conn_str = container.resolve("connection_string")
```

--------------------------------

### Register Class Without Base Interface

Source: https://github.com/bobthemighty/punq/blob/main/README.md

Register a concrete class directly without an abstract base class. Useful for simple services that don't need polymorphism. Dependencies are still automatically injected.

```python
class Greeter:
    def __init__(self, config_reader: ConfigReader):
        self.config = config_reader.get_config()

    def greet(self):
        print(self.config['greeting'])

container.register(Greeter)
container.resolve(Greeter).greet()
```

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