Utility function for padding an array by appending `pad_amt` zeros along any `axis`. Non-symmetric. The ideas behind this snippet led to the `np.pad` improvements introduced in NumPy 1.8. This is licensed under the modified BSD.

_pad_asymmetric.py

import numpy as np

def _pad_asymmetric_zeros(arr, pad_amt, axis=-1):
    """Pads `arr` by `pad_amt` along specified `axis`"""
    if axis == -1:
        axis = arr.ndim - 1

    zeroshape = tuple([x if i != axis else pad_amt
                       for (i, x) in enumerate(arr.shape)])

    return np.concatenate((arr, np.zeros(zeroshape, dtype=arr.dtype)),
                          axis=axis)