How Can I Retrieve Return Values from Child Processes in Multiprocessing?

How to Capture Return Values from Process-Based Functions in Multiprocessing

In multiprocessing applications, a common need arises to retrieve the return values of functions executed by child processes. The reason this isn't readily accessible is that child processes cannot directly pass back values to the main process. However, there are techniques to effectively capture these values.

In the given example, a list of worker processes is created to perform specific tasks and return their process numbers. However, when attempting to access the return values from the Process objects stored in the "jobs" list, it becomes evident that these values are not directly stored in their attributes.

To overcome this challenge, a different approach is required. One effective solution involves the use of a shared variable, such as a dictionary. This shared variable allows communication between the child processes and the main process.

In the modified example, a Manager is created to manage the shared memory among processes. A dictionary, return_dict, is initialized and passed as an argument to the worker function. Within the worker, the process number is assigned as the key and the process number itself as the value.

Once all processes complete their execution, the main process joins the child processes and then accesses the shared return_dict. By iterating over its values, the desired return values of the child processes are obtained. This approach effectively captures the return values through inter-process communication.

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