Yeah, the stdlib bz2 module does release the GIL for the time of the compression (though it locks the compressor object simultaneously): https://github.com/pyth

Yeah, the stdlib bz2 module does release the GIL for the time of the compression (though it locks the compressor object simultaneously): https://github.com/python/cpython/blob/d4b93e21c2664d6a78e0656e7a7be0807be1c352/Modules/_bz2module.c#L242 https://github.com/python/cpython/blob/d4b93e21c2664d6a78e06...