bgb snapshot reader

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# vim: sts=4 sw=4 et

import sys
from struct import unpack
from array import array

def read_snspshot(snapshot_name):
    def readasciiz(f):
        res = b''
        ch = f.read(1)
        while (ch != b'') and (ch != b'\x00'):
            res = res + ch
            ch = f.read(1)
        return res.decode('u8')

    def readblock(f):
        len = unpack('<L', f.read(4))[0]
        if len == 0:
            return None
        if len == 1:
            return [len, unpack('B', f.read(1))[0]]
        elif len == 2:
            return [len, unpack('<H', f.read(2))[0]]
        elif len == 4:
            return [len, unpack('<L', f.read(4))[0]]
        else:
            data = array('B')
            data.fromfile(f, len)
            return data

    snapshot = {}
    with open(snapshot_name, 'rb') as f:
        name = readasciiz(f)
        while (name):
            data = readblock(f)
            snapshot[name] = data
            name = readasciiz(f)
    return snapshot

# read the snapshot to the dict
snapshot = read_snspshot(sys.argv[1])

# pretty-print the snapshot dict
for k, v in snapshot.items():
    if v is None: 
        print(k)
    elif type(v) is array:
        if len(v) <= 16:
            print("{} [{:s}]".format(k, ', '.join(['0x{:02x}'.format(x) for x in v])))
        else:
            print("{} ARRAY[{:d}]".format(k, len(v)))
    elif type(v) is list:
        print("{} 0x{:0{}x}".format(k, v[1], v[0] * 2))