Python: how to share an object instance across multiple invocations of a script

Question

I'm use a library which provides a python interface to an external program. This allows me to create:

foo = Foo()

The code above starts a new instance of the Foo program that I can control from within python.

I have a python scripts which needs to be invoked multiple times and depending on external parameters, tell a single instance of the external Foo program to do different things. Obvious I can't do

foo = Foo() everytime,

since that creates a new instance of Foo every time my script runs.

What I want to do is to create foo= Foo() once, and have multiple invocations share the same instance. Currently I'm thinkibng of just creating it once, serialize it, and have my scripts deserialize it. Does this approach work? Is there a better alternative?

Thanks!!

Community · Accepted Answer · 2017-05-23 12:04:24Z

3

This can be done if you follow an approach similar to that given in this answer. Or you can use Pyro, which is compared to multiprocessing in this answer.

edited May 23, 2017 at 12:04

CommunityBot

11 silver badge

answered Jun 26, 2011 at 1:43

Vinay Sajip

100k15 gold badges184 silver badges196 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Zach Kelling · Accepted Answer · 2011-06-26 02:44:39Z

1

You might be able to use pickle. Here's a simple example:

import os, pickle

class Foo(object):
    def __init__(self, bar):
        self.bar = bar

# use previous pickled instance if found
if os.path.exists('foo.pickle'):
    with open('foo.pickle') as f:
        foo = pickle.load(f)
else:
    foo = Foo(42)

# print current foo.bar
print foo.bar

# change foo.bar and pickle
foo.bar = raw_input('new bar: ')
with open('foo.pickle', 'w') as f:
    pickle.dump(foo, f)

answered Jun 26, 2011 at 2:44

Zach Kelling

54.1k15 gold badges112 silver badges108 bronze badges

3 Comments

wk1989 Over a year ago

I tried doing that actually, I got a message saying "Can't pickle 'lock' object: <thread.lock object at ... >". I'm looking into it now.

Zach Kelling Over a year ago

Yeah, it has limitations which you may/may not be able to work around to do what you want: docs.python.org/library/…

lunixbochs Over a year ago

if you're using a lock, you probably need to take another path like sockets or pipes to provide locked access to your class

Keith · Accepted Answer · 2011-06-26 05:31:55Z

0

You can change the design so that Foo() just connects you to an existing process, and then you create a new function, call it startFoo() that you previously call once (or if Foo() fails). Even better would be to make the program that Foo() connects to a service that you connect to over a socket. You might also want to just switch to the multiprocessing module.

answered Jun 26, 2011 at 5:31

Keith

43.2k11 gold badges62 silver badges77 bronze badges

1 Comment

wk1989 Over a year ago

Yeah I think that's what i'll have to do seeing as I can't serialize the the Foo object easily.

Collectives™ on Stack Overflow

Python: how to share an object instance across multiple invocations of a script

3 Answers 3

Comments

3 Comments

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

3 Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related