Cannot unpickle in __main__ in Python 2 about chopsticks

[Ian2020]

Hi, great project. Is there any workaround for this issue?

[lordmauve]

There are several. The cleanest one is is to make sure that the functions you want to call remotely are in a separate module to your __main__ module. This is good organisational practice anyway.

[Ian2020]

Sorry, I should have thought of that before I posted! Thanks very much.

[lordmauve]

If you want a single-file solution, there is one, but it's subtle and cludgey:

Say your script is called my_script.py:

def my_remote_func():
    ...

if __name__ == '__main__':
    from my_script import my_remote_func
    # now my_remote_func is my_script.my_remote_func, which can be unpickled
    from chopsticks.tunnel import Tunnel
    Tunnel(hostname).call(my_remote_func)

[Ian2020]

Very kind of you to provide that snippet - I will use it. Just trying out Chopsticks quickly for first time today and was too lazy to use modules! It's already saved me some time.

[romanlevin]

The same (or a very similar) issue exists in Python 3, with a much less friendly error:

chopsticks.tunnel.RemoteException: Host 'local' raised exception; traceback follows

    Traceback (most recent call last):
      File "bubble.py", line 139, in wrapper
      File "bubble.py", line 152, in handle_call_thread
      File "<frozen importlib._bootstrap>", line 969, in _find_and_load
      File "<frozen importlib._bootstrap>", line 958, in _find_and_load_unlocked
      File "<frozen importlib._bootstrap>", line 664, in _load_unlocked
      File "<frozen importlib._bootstrap>", line 634, in _load_backward_compatible
      File "bubble.py", line 119, in load_module
      File "controller://run.py", line 3, in <module>
      File "<frozen importlib._bootstrap>", line 969, in _find_and_load
      File "<frozen importlib._bootstrap>", line 958, in _find_and_load_unlocked
      File "<frozen importlib._bootstrap>", line 664, in _load_unlocked
      File "<frozen importlib._bootstrap>", line 634, in _load_backward_compatible
      File "bubble.py", line 119, in load_module
      File "controller://chopsticks/tunnel.py", line 358, in <module>
        class SubprocessTunnel(PipeTunnel):
      File "controller://chopsticks/tunnel.py", line 366, in SubprocessTunnel
        '__bubble = sys.stdin.read(%d); ' % len(bubble) +
    TypeError: object of type 'NoneType' has no len()

[lordmauve]

@romanlevin - that's actually caused by issue #6.

Specifically, issue #6 means you can't import chopsticks on the remote host at the moment. If you move your chopsticks imports to the if __name__ == __main__ block, then it should work.

[romanlevin]

@lordmauve oh I see, thanks!

[lordmauve]

The solution to issue #17 will fix this issue also.