There is a library called threading in Python and it uses threads (rather than just processes) to implement parallelism. This may be surprising news if you know about the Python’s Global Interpreter Lock, or GIL, but it actually works well for certain instances without violating the GIL. And this is all done without any overhead — simply define functions that make I/O requests and the system will handle the rest.
Global Interpreter Lock
The Global Interpreter Lock reduces the usefulness of threads in Python (more precisely CPython) by allowing only one native thread to execute at a time. This made implementing Python easier to implement in the (usually thread-unsafe) C libraries and can increase the execution speed of single-threaded programs. However, it remains controvertial because it prevents true lightweight parallelism. You can achieve parallelism, but it requires using multi-processing, which is implemented by the eponymous library multiprocessing. Instead of spinning up threads, this library uses processes, which bypasses the GIL.
It may appear that the GIL would kill Python multithreading but not quite. In general, there are two main use cases for multithreading:
- To take advantage of multiple cores on a single machine
- To take advantage of I/O latency to process other threads
In general, we cannot benefit from (1) with threading but we can benefit from (2).
