Question

I want to know if a function is defined for an instance of a class

class c(object):
  def func(self): pass
cc = c()

>>> is_function_defined_for_instance(cc,'func')
True
>>> is_function_defined_for_instance(cc,'cnuf')
False

my cleanest attempts at the function is:

def is_function_defined_for_instance(instance,function):
  return callable(getattr(instance,function,None))

# returns True iff function is defined for class of instance (not super classes)
def is_function_defined_for_instance(instance,function):
  return bool(instance.__class__.__dict__.get(function))

is there a built-in or a nicer way to accomplish what I’m looking for?

Answer 1

>>> def is_func(instance, func):
    test = getattr(instance, func, None)
    if test and hasattr(test, '__call__'):
        return True

>>> is_func('', 'len')
>>> is_func({}, 'fromkeys')
True

or you could use inspect module:

>>> import inspect
>>> test = getattr(cc, 'func', None)
>>> inspect.ismethod(test)
True