Remember that duck typing + default values + args + kwargs is usually more idiomatic than function overloading in python.

Don't try to code in python like you code in another language.

Also, think about what your API is conveying. Overloading may make it less clear.

The snippet from this article is a good example of when not to do it:

    def area (l, b): 
      return length * breadth;


    def area(r):
      return 3.14 * radius * radius

Here, you have 2 functions that do 2 fundamentally different things. One is calculating an area for a circle. The other one is for a rectangle. When you have 2 different signatures, it's often a sign the process is very different, and you should signal that in your API.

If you scan code using those, your brain cannot quickly parse it. It needs to process "area(), ok but of what, well, it has only x param, so I guess this is for z". The overloading gimmick has little value for the reader, but a real cost (not to mention in python it actually slows the run time)

The better solution is simply to make it explicitly 2 functions with good names:

    def rectangle_area (l, b): 
      return length * breadth;

Or, most likely, put them in separated namespaces (using a module or a class), which does the same.

    import circle

    circle.area(r)       

It's very easy to abuse overloading because it tickles our need for refactoring. But it's a tool to solve a problem, not an end by itself.