Convert a number of bytes into a human readable memory usage

humanbytes.py

memory_symbols = ('K', 'M', 'G', 'T', 'P', 'E', 'Z', 'Y')
memory_size = dict(((s,1 << (i+1)*10) for i,s in enumerate(memory_symbols)))

def convert_bytes(b):
    '''Convert a number of bytes into a human readable memory usage'''
    if b is None:
        return '#NA'
    for s in reversed(memory_symbols):
        if b >= memory_size[s]:
            value = float(b) / memory_size[s]
            return '%.1f%sB' % (value, s)
    return "%sB" % b