simple serializer and deserializer for Python

custom-serializer.py

import re
 
class Serializer(object):
    def __init__(self):
        self.s, self.r = "", {}
 
    def write(self, o):
        self.s += self.to_s(o); return self.s
    
    def to_s(self, o):
        if o is None: return "N"
        if o is True: return "T"
        if o is False: return "F"
        if isinstance(o, int): return "I%i" % o
        if isinstance(o, str): return "S%r" % o
        if id(o) in self.r: return "R%i" % self.r[id(o)]
        self.r[id(o)] = len(self.r)
        if isinstance(o, tuple): return self.seq_to_s("(", o)
        if isinstance(o, list): return self.seq_to_s("[", o)
        if isinstance(o, dict): return self.seq_to_s("{", o.items())
        raise ValueError, o
    
    def seq_to_s(self, tp, l):
        return "%s%s;" % (tp, "".join(self.to_s(e) for e in l))
 
class Deserializer(object):
    def __init__(self, s):
        self.t = iter(re.findall(r"[NTFISR(\[{;]|-?\d+|'[^']*'|\"[^\"]*\"", s)).next
        self.r = {}
    
    def read(self, t=None):
        if t is None: t = self.t()
        if t == "N": return None
        if t == "T": return True
        if t == "F": return False
        if t == "I": return int(self.t())
        if t == "S": return self.t()[1:-1].decode("string-escape")
        if t == "R": return self.r[int(self.t())]
        if t == "(": return self.register(tuple(self.read_seq([])))
        if t == "[": return self.read_seq(self.register([]))
        if t == "{": d = self.register({}); d.update(self.read_seq([])); return d
        raise ValueError, t
        
    def read_seq(self, seq):
        t = self.t()
        while t != ';':
            seq.append(self.read(t)); t = self.t()
        return seq
    
    def register(self, o):
        self.r[len(self.r)] = o; return o