[fabioz]

Actually, you get the speed increase if using threads on python with numpy because numpy will release the GIL internally, so, operations using numpy will actually run in parallel (i.e.: c libraries can release the GIL and do get the performance benefits when using multiple processors -- although yes, when you get back to running python code that won't be parallel due to the GIL).

[blitzar]

My genuine deep love for numpy extends to them doing these things without me knowing anything about it.

[KeplerBoy]

That's something I worry about when reading about future Python releases without GIL.

Will people just throw more and more threads at unfathomably slow Python code to get somewhat fast results?