Methods with the same name in one class in Python

Question

You can have a function that takes in a variable number of arguments.

def my_method(*args, **kwds):
    # Do something

# When you call the method
my_method(a1, a2, k1=a3, k2=a4)

# You get:
args = (a1, a2)
kwds = {'k1':a3, 'k2':a4}

So you can modify your function as follows:

def my_method(*args):
    if len(args) == 1 and isinstance(args[0], str):
        # Case 1
    elif len(args) == 2 and isinstance(args[1], int):
        # Case 2
    elif len(args) == 2 and isinstance(args[1], str):
        # Case 3

You can't. There are not overloads or multimethods or similar things. One name refers to one thing. As far as the language is concerned anyway, you can always emulate them yourself... You could check types with isinstance (but please do it properly - e.g. in Python 2, use basestring to detect both strings and unicode), but it's ugly, generally discouraged and rarely useful. If the methods do different things, give them different names. Consider polymorphism as well.

Short answer: you can't (see this previous discussion). Typically you'd use something like (you could add more type checking and reorder):

def my_method(self,parameter_A, parameter_B=None):
  if isinstance(parameter_B, int):
    print parameter_A * parameter_B
  else:
    print parameter_A
    if parameter_B is not None:
      print parameter_B

Using Python 3.5 or higher, you can use @typing.overload to provide type annotations for overloaded functions/methods.

From the docs:

@overload
def process(response: None) -> None:
    ...
@overload
def process(response: int) -> tuple[int, str]:
    ...
@overload
def process(response: bytes) -> str:
    ...
def process(response):
    <actual implementation>

You can try multimethods in Python:

http://www.artima.com/weblogs/viewpost.jsp?thread=101605

But I don't believe multimethod is a way to go. Rather objects that you pass to a method should have common interface. You are trying to achieve method overloading similar to the one in C++, but it is very rarely required in Python. One way to do this is a cascade of ifs using isinstance, but that's ugly.