python: what happens when an object is passed in multiprocessing.Process?

Question

p = Process(target=f, args=(myObject,))
p.start()
p.join()

From experimentation, inside of function f(), I can access myObject fine and its members appears to be intact, even though presumably we're in a different process. Printing id(myObject) in the current function and in f() returns the same number.

Is Python secretly performing IPC when myObject is accessed inside of f()?

Answer 1

As Winston wrote: on Unix the process will be forked and the forked process is basically a full copy of the parent process (that's why the id is identical).

Answer 2

The actual process depends on whether you are running unix or windows.

On *nix, fork() is used which creates a complete copy of your process.

On windows, I believe the object is pickled (see the pickle module) and sent over some IPC channel.