code: def method_cache(method, cache_wrapper=None):
      """
      Wrap lru_cache to support storing the cache data in the object instances.
  
      Abstracts the common paradigm where the method explicitly saves an
      underscore-prefixed protected property on first call and returns that
      subsequently.
  
      >>> class MyClass:
      ...     calls = 0
      ...
      ...     @method_cache
      ...     def method(self, value):
      ...         self.calls += 1
      ...         return value
  
      >>> a = MyClass()
      >>> a.method(3)
      3
      >>> for x in range(75):
      ...     res = a.method(x)
      >>> a.calls
      75
  
      Note that the apparent behavior will be exactly like that of lru_cache
      except that the cache is stored on each instance, so values in one
      instance will not flush values from another, and when an instance is
      deleted, so are the cached values for that instance.
  
      >>> b = MyClass()
      >>> for x in range(35):
      ...     res = b.method(x)
      >>> b.calls
      35
      >>> a.method(0)
      0
      >>> a.calls
      75
  
      Note that if method had been decorated with ``functools.lru_cache()``,
      a.calls would have been 76 (due to the cached value of 0 having been
      flushed by the 'b' instance).
  
      Clear the cache with ``.cache_clear()``
  
      >>> a.method.cache_clear()
  
      Same for a method that hasn't yet been called.
  
      >>> c = MyClass()
      >>> c.method.cache_clear()
  
      Another cache wrapper may be supplied:
  
      >>> cache = functools.lru_cache(maxsize=2)
      >>> MyClass.method2 = method_cache(lambda self: 3, cache_wrapper=cache)
      >>> a = MyClass()
      >>> a.method2()
      3
  
      Caution - do not subsequently wrap the method with another decorator, such
      as ``@property``, which changes the semantics of the function.
  
      See also
      http://code.activestate.com/recipes/577452-a-memoize-decorator-for-instance-methods/
      for another implementation and additional justification.
      """
      cache_wrapper = cache_wrapper or functools.lru_cache()
  
      def wrapper(self, *args, **kwargs):
          # it's the first call, replace the method with a cached, bound method
          bound_method = types.MethodType(method, self)
          cached_method = cache_wrapper(bound_method)
          setattr(self, method.__name__, cached_method)
          return cached_method(*args, **kwargs)
  
      # Support cache clear even before cache has been created.
      wrapper.cache_clear = lambda: None
  
      return wrapper
  
imports: import types
  import functools
label_desc: Use image node_id 1 for calling a global function with example usage: method_cache(method, cache_wrapper) and returns: wrapper, cached_method