zope-component

from zope.interface import Interface, implementer from zope.component import provideUtility, getUtility, queryUtility, ComponentLookupError # 1. Define an Interface class IGreeter(Interface): """The Greeter interface provides a greeting method.""" def greet(name: str) -> str: """Say hello to the given name.""" # 2. Implement the Interface @implementer(IGreeter) class HelloGreeter: """A simple greeter component.""" def greet(self, name: str) -> str: return f"Hello, {name}!" # 3. Register the Utility # A utility is a component looked up by an interface and an optional name. # We can register an instance of the Greeter. my_greeter_instance = HelloGreeter() provideUtility(my_greeter_instance, IGreeter, name='default-greeter') # You can also register without a name for a singleton utility for the interface provideUtility(HelloGreeter(), IGreeter) # No name, becomes default for IGreeter # 4. Look up and use the Utility # Using getUtility (raises ComponentLookupError if not found) try: default_greeter = getUtility(IGreeter) print(f"Default greeting: {default_greeter.greet('World')}") except ComponentLookupError: print("Default greeter not found.") try: named_greeter = getUtility(IGreeter, name='default-greeter') print(f"Named greeting: {named_greeter.greet('Alice')}") except ComponentLookupError: print("Named greeter not found.") # Using queryUtility (returns None if not found, or a default value if specified) missing_greeter = queryUtility(IGreeter, name='non-existent') print(f"Querying missing greeter (should be None): {missing_greeter}") fallback_greeter = queryUtility(IGreeter, name='non-existent', default='Fallback') print(f"Querying with fallback: {fallback_greeter}")