python_start.py

SUFFIXES = {1000: ['KB','MB','GB','TB','PB','EB','ZB','YB'],
             1024: ['KiB','MiB','GiB','TiB','PiB','EiB','ZiB','YiB']}

def approximate_size(size,a_kilobyte_is_1024_bytes=True):
    '''Conver a file size to human-readable form

    keyword arguments:
    size -- file size in byes
    a_kilobyte_is_1024_bytes -- if True(default),use multiples of 1024
                                if False, use multiples of 1000
    
    Returns: string

    '''
    if size < 0:
        raise ValueError('number must be non-negative')
    
    multiple = 1024 if a_kilobyte_is_1024_bytes else 1000
    for suffix in SUFFIXES[multiple]:
        size /= multiple
        if size < multiple:
            return '{0:.1f} {1}'.format(size,suffix)
    
    raise ValueError('number too large')

if __name__ == "__main__":
    print(approximate_size(1000000000000, False))
    print(approximate_size(1000000000000))