Basic SI

gistfile1.py

#!/usr/bin/python  

def __unit(val):
    if not val[-1:].isalpha():
        return val

    if len(val) <= 1 or val[-2:-1].isalpha():
        raise RuntimeError('invalid units')

    i = int(val[:-1])
    char = val[-1:]

    multiple_table = {
        'M' : int(10e6), 
        'k' : int(10e3),
        'h' : int(10e2), 
    }
    if not char in multiple_table:
        raise RuntimeError('unsupported unit (%s)' % char)

    return str(multiple_table[char] * i)

print __unit('126k')
print __unit('3M')
print __unit('4')