Converts a human-readable memory string (e.g. "256 GiB") into an integral byte count.

parse_memory_string.py

import re

def parse_memory_string(mem_str):
        """
        Returns the number of bytes represented by a string ``mem_str`` matching the following
        regex: ::

                r'^(0|[1-9][0-9]*) (byte|bytes|KiB|MiB|GiB|TiB)'

        If ``mem_str`` does not match this regex, then ``None`` is returned.
        """

        memory_regex = r'^(0|[1-9][0-9]*) (byte|bytes|KiB|MiB|GiB|TiB)'
        mem_pat      = re.compile(memory_regex)
        match        = mem_pat.match(mem_str)

        if match is None:
                return

        assert len(match.groups()) == 2
        base = int(match.groups()[0])
        
        return base * {
                'byte':  1,
                'bytes': 1,
                'KiB':   2 ** 10,
                'MiB':   2 ** 20,
                'GiB':   2 ** 30,
                'TiB':   2 ** 40
        }[match.groups()[1]]