Dataclass Commands

An alternative command syntax is to use dataclasses with a __call__ method. To support this pattern, Cyclopts provides the "call_if_callable" result action, which can be composed with other result actions.

Basic Example

Here's a simple example using the dataclass command pattern:

# greeter.py
from dataclasses import dataclass, KW_ONLY
from cyclopts import App

app = App(result_action=["call_if_callable", "print_non_int_sys_exit"])

@app.command
@dataclass
class Greet:
    """Greet someone with a message."""

    name: str = "World"
    _: KW_ONLY
    formal: bool = False

    def __call__(self):
        greeting = "Hello" if self.formal else "Hey"
        return f"{greeting} {self.name}."

if __name__ == "__main__":
    app()

Running this application:

$ python greeter.py greet
Hey World.

$ python greeter.py greet Alice
Hey Alice.

$ python greeter.py greet Bob --formal
Hello Bob.

How It Works

The result_action=["call_if_callable", "print_non_int_sys_exit"] creates a pipeline:

call_if_callable: After parsing, Cyclopts creates an instance of the Greet dataclass. This action checks if the result is callable (it is, because of __call__), and calls it with no arguments.
print_non_int_sys_exit: Takes the string returned by __call__ and prints it, then exits.

Without "call_if_callable", the app would try to print the dataclass instance itself instead of calling it and printing the result.