import re


def mixed_sort(list_of_elements):
    """
    https://arcpy.wordpress.com/2012/05/11/sorting-alphanumeric-strings-in-python/

    Args:
       a list of

    Returns:
      list: ordered list

    Example::

        a = ['A1','A10','A2','A20']
        mixed_sort(a)
        > ['A1','A2', 'A10', 'A20']

    """
    convert = lambda text: int(text) if text.isdigit() else text
    alphanum_key = lambda key: [convert(c) for c in re.split("([0-9]+)", key)]
    return sorted(list_of_elements, key=alphanum_key)