# -*- coding: utf-8 -*-
"""
immutablize instance sample
"""
import operator
import types
class A(object):
def __init__(self, a, b):
self.a = a
self.__b = b
def say(self):
print self.a,self.__b
def incr(self):
self.a = self.a + 100
def incr2(self):
self.incr()
def frozen_instance(instance):
def new__(_cls, inst):
return tuple.__new__(_cls, tuple([inst] + inst.__dict__.values()))
def repr__(self):
return repr(self[0])
def getattr__(self, name):
return types.MethodType(self[0].__class__.__dict__[name], self, self[0].__class__)
klass = instance.__class__
nlass = type('Frozen'+klass.__name__,(tuple,),
dict(__new__=new__, __repr__=repr__, __getattr__=getattr__)
)
for i,k in enumerate(instance.__dict__.keys()):
setattr(nlass, k, property(operator.itemgetter(1+i)))
return nlass(instance)
if __name__ == '__main__':
a = A(1, "aaa")
print "[a]"
a.say()
frozen_a = frozen_instance(a)
print "[frozen_a]"
frozen_a.say()
a.incr()
a.say()
frozen_a.incr2()
-----outputs-----
[a]
1 aaa
[frozen_a]
1 aaa
101 aaa
Traceback (most recent call last):
File "fix.py", line 58, in <module>
frozen_a.incr2()
File "fix.py", line 22, in incr2
self.incr()
File "fix.py", line 19, in incr
self.a = self.a + 100
AttributeError: can't set attribute
