python resettable instance method memoization decorator

Question

I\'m attempting to build a decorator for an instance method of a class that will memoize the result. (This has been done a million times before) However, I\'d like the optio

Answer 1

Building upon the answer to the original question given by @aix I have created a class that I think could improve it. The main feature is that the cached values are stored as a property of the instance whose method is being decorated, hence it is very easy to reset them.

class memoize(object):
  def __init__(self, func):
    #print "Init"
    self.func = func

  def __call__(self, *args):
    #print "Call"
    if not self.func in self.cache:
        self.cache[self.func] = {}
    try:
        return self.cache[self.func][args]
    except KeyError:
        value = self.func(*args)
        self.cache[self.func][args] = value
        return value
    except TypeError:
        # uncachable -- for instance, passing a list as an argument.
        # Better to not cache than to blow up entirely.
        return self.func(*args)

  def __repr__(self):
    """Return the function's docstring."""
    return self.func.__doc__

  def __get__(self, obj, objtype):
    """Support instance methods."""
    #print "Get", obj, objtype
    fn = functools.partial(self.__call__, obj)
    try:
        self.cache = obj.cache
    except:
        obj.cache = {}
        self.cache = obj.cache
    #print self.cache
    return fn

As an example of usage:

class MyClass(object):
    def __init__(self,data):
        self.data = data

    def update(self,data):
        self.data = data
        self.cache = {}

    @memoize
    def func1(self,x):
        print "Computing func1"
        return "I am func1 of %s. Data is %s. x is %s\n" % (self, self.data, x)

    @memoize
    def func2(self,x):
        print "Computing func2"
        return "I am func2 of %s. Data is %s. x is %s\n" % (self, self.data, x)

    def func3(self,x):
        print "Computing func3"
        return "I am func3 of %s. Data is %s. x is %s\n" % (self, self.data, x)

mc1 = MyClass("data1")
mc2 = MyClass("data2")
mc3 = MyClass("data3")

print mc1.func1(1) 
print mc1.func1(1) 
print mc1.func2(1) 
print mc1.func2(1) 
print mc1.func3(1) 
print mc1.func3(1) 

print mc2.func1(1) 
print mc2.func1(1) 
print mc2.func2(1) 
print mc2.func2(1) 
print mc2.func3(1) 
print mc2.func3(1) 

print "Update mc1\n"
mc1.update("data1new")

print mc1.func1(1) 
print mc1.func2(1) 
print mc1.func3(1) 
print mc2.func1(1) 
print mc2.func2(1) 
print mc2.func3(1) 

gets as output:

Computing func1
I am func1 of <__main__.MyClass object at 0x100470fd0>. Data is data1. x is 1

I am func1 of <__main__.MyClass object at 0x100470fd0>. Data is data1. x is 1

Computing func2
I am func2 of <__main__.MyClass object at 0x100470fd0>. Data is data1. x is 1

I am func2 of <__main__.MyClass object at 0x100470fd0>. Data is data1. x is 1

Computing func3
I am func3 of <__main__.MyClass object at 0x100470fd0>. Data is data1. x is 1

Computing func3
I am func3 of <__main__.MyClass object at 0x100470fd0>. Data is data1. x is 1

Computing func1
I am func1 of <__main__.MyClass object at 0x100476050>. Data is data2. x is 1

I am func1 of <__main__.MyClass object at 0x100476050>. Data is data2. x is 1

Computing func2
I am func2 of <__main__.MyClass object at 0x100476050>. Data is data2. x is 1

I am func2 of <__main__.MyClass object at 0x100476050>. Data is data2. x is 1

Computing func3
I am func3 of <__main__.MyClass object at 0x100476050>. Data is data2. x is 1

Computing func3
I am func3 of <__main__.MyClass object at 0x100476050>. Data is data2. x is 1

Update mc1

Computing func1
I am func1 of <__main__.MyClass object at 0x100470fd0>. Data is data1new. x is 1

Computing func2
I am func2 of <__main__.MyClass object at 0x100470fd0>. Data is data1new. x is 1

Computing func3
I am func3 of <__main__.MyClass object at 0x100470fd0>. Data is data1new. x is 1

I am func1 of <__main__.MyClass object at 0x100476050>. Data is data2. x is 1

I am func2 of <__main__.MyClass object at 0x100476050>. Data is data2. x is 1

Computing func3
I am func3 of <__main__.MyClass object at 0x100476050>. Data is data2. x is 1