Global Interpreter Lock and access to data (eg. for NumPy arrays)

Question

I am writing a C extension for Python, which should release the Global Interpreter Lock while it operates on data. I think I have understood the mechanism of the GIL fairly

Answer 1

Can I access data in a Python object while the thread does not own the GIL?

No you cannot.

Answer 2

Is this safe?

Strictly, no. I think you should move the calls to PyArray_SIZE and PyArray_DATA outside the GIL-less block; if you do that, you'll be operating on C data only. You might also want to increment the reference count on the object before going into the GIL-less block and decrement it afterwards.

After your edits, it should be safe. Don't forget to decrement the reference count afterwards.