Simple pure python function to return an empty n-byte-aligned array.

empty_aligned.py

import numpy as np

def empty_aligned(shape, dtype='float64', order='C', n=None):
    '''empty_aligned(shape, dtype='float64', order='C', n=None)
    Function that returns an empty numpy array that is n-byte aligned,
    where ``n`` is determined by inspecting the CPU if it is not
    provided.
    The alignment is given by the final optional argument, ``n``. If ``n`` is
    not set then the default alignment is used.
    The rest of the arguments are as per :func:`numpy.empty`.
    '''

    if n is None:
        n = 1

    itemsize = np.dtype(dtype).itemsize

    # Apparently there is an issue with numpy.prod wrapping around on 32-bits
    # on Windows 64-bit. This shouldn't happen, but the following code
    # alleviates the problem.
    if not isinstance(shape, (int, np.integer)):
        array_length = 1
        for each_dimension in shape:
            array_length *= each_dimension

    else:
        array_length = shape

    # Allocate a new array that will contain the aligned data
    _array_aligned = np.empty(array_length*itemsize+n, dtype='int8')

    # We now need to know how to offset _array_aligned
    # so it is correctly aligned
    _array_aligned_offset = (n - _array_aligned.ctypes.data)%n

    array = np.frombuffer(
            _array_aligned[_array_aligned_offset:_array_aligned_offset-n].data,
            dtype=dtype).reshape(shape, order=order)

    return array