to_bytes.py

import re

def to_bytes(value):
    """
    Convert a size string with an exponent into bytes.
    
    Input:
        value (str): Size string
    Output:
        bytes (int): Size in bytes
    """
    units = [ 'B', 'K', 'M', 'G', 'T', 'P', 'E' ]

    # Match any floating point number followed by an optional unit
    m = re.search(r'^([0-9]*\.?[0-9]+)([%s])?b?$' % ''.join(units), value, re.IGNORECASE)
    if not m:
        raise ValueError('invalid format %s' % value)
    num = float(m.group(1))
    if m.group(2):
        unit = m.group(2).upper()
    else:
        unit = 'B'

    # Perform byte calculation
    exp = units.index(unit)
    byte = num * 1024 ** exp
    
    return byte