Introduction

python-safethread uses with branch() as children: to spawn threads. This incorporates exception handling, cancellation, and deadlock detection.

``` from future import shared_module from socket import socket from threadtools import branch

def main(): server_socket = socket(...) server_socket.bind(...) run_server(server_socket)

def run_server(server_socket): with server_socket: # Close the server socket when we exit with branch() as clients: clients.add(handle_client, *server_socket.accept())

def handle_client(client_socket, addr): with client_socket: # Close the client socket when we exit ... utilize client_socket ... data = client_socket.read() ```

You'll end up with a stack something like this:

main - run_server - socket.accept # Main thread |- handle_client - socket.read # First client thread \- handle_client - socket.read # Second client thread

If any one of the threads fails, the rest will be cancelled, and the main thread will wait in the with branch() as clients: line until the children have exited.

Generally, only IO operations (accessing a file or socket) or a condition will react to being cancelled, raising a Cancelled exception (caught by the with branch() as clients:.) CPU-bound operations will ignore it, running to completion (and thus allowing them to leave things in a sane state.)