What is the best way of allocating array of bytes in Cython and passing it back to Python?

Question

I have a Cython function like cdef generate_data(size) where I'd like to:

• initialise an array of bytes of length size
• call external (C) function to populate the array using array ptr and size
• return the array as something understandable by Python (bytearray, bytes, your suggestions)

I have seen many approaches on the internet but I'm looking for the best/recommended way of doing this in my simple case. I want to:

• avoid memory reallocations
• avoid using numpy
• ideally use something that works in Python 3 and 2.7, although a 2.7 solution is good enough.

I'm using Cython 0.20.

Answer 1

For allocating memory, I have you covered.

After that, just take a pointer (possibly at the data attribute if you use cpython.array.array like I recommend) and pass that along. You can return the cpython.array.array type and it will become a Python array.