How to Build a Simple gRPC-Style Data Service in Python

from dataclasses import dataclass
from typing import Optional


@dataclass
class User:
    id: int
    name: str
    email: str


class UserService:
    """Simple gRPC-style service contract for beginner learners."""

    def get_user(self, user_id: int) -> Optional[User]:
        """Simulated gRPC GetUser RPC."""
        # Mock database
        users = {
            1: User(1, "Alice", "alice@example.com"),
            2: User(2, "Bob", "bob@example.com"),
        }
        return users.get(user_id)

    def create_user(self, name: str, email: str) -> User:
        """Simulated gRPC CreateUser RPC."""
        # In real gRPC, this would send a request to a server
        return User(id=3, name=name, email=email)


# gRPC-style message classes
@dataclass
class GetUserRequest:
    user_id: int


@dataclass
class UserResponse:
    user: Optional[User]


if __name__ == "__main__":
    service = UserService()

    # Demonstrate RPC-style calls
    request = GetUserRequest(user_id=1)
    response = UserResponse(user=service.get_user(request.user_id))
    print(f"GetUser(1) -> {response.user}")

    request = GetUserRequest(user_id=99)
    response = UserResponse(user=service.get_user(request.user_id))
    print(f"GetUser(99) -> {response.user}")

    new_user = service.create_user("Charlie", "charlie@example.com")
    print(f"CreateUser -> {new_user}")