How to Share Data Between Processes in Python Multiprocessing?

Global Variable Updates Not Returned to Parent in Multiprocessing

In multiprocessing, a new Python instance is created for each process, resulting in distinct global states. Therefore, updates to global variables made by child processes remain invisible to the parent process.

Unpickable Objects

Multiprocessing relies on serialization through pickle. If the objects you wish to exchange cannot be pickled, they cannot be shared between processes. This includes any data stored within Manager objects or transmitted via Queues.

Alternative Approaches

• Custom State Management: Consider using a solution outside of the multiprocessing module, such as shared memory or a database, to manage process-wide state.
• Subclassing and Pickling: If the unpicklable object is a Python class, investigate the possibility of subclassing it and implementing getstate and setstate methods to enable pickling.
• Data Exchange via Queues: Instead of passing unpicklable objects directly, consider transferring the required data as strings or other serializable formats via Queues. This allows child processes to manipulate the data without requiring object serialization.

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