if the names is an empty list, then f will be "-1". I think this will cause problem

You are welcome. Happy coding :)

@Chris0lsen, map and filter are present in Python by default, while reduce is a part of functools module only in Python 3.

@nagendra226, want to learn? Then google stuff, and use it - nobody's going to spoonfeed you, and nobody will help you with dumb questions all the time (especially, when google can find approximately 81,400 pages in just 0.43 seconds if you search for "what is functools").

functools is a PYthon library that gives the user access to functional programming methods such as map, filter and reduce

I've fixed the test cases anyway, so your code should work now.

I am not modifying any input

I dont know how to modify

Pick one.

Don't use .popitem() because you're messing up the tests with it.

The line, k = m.popitem() modifies the input.

Don't modify the input.

Please don't raise an issue if there is a promblem with your code. Post a question instead.
Also, make sure you flag your post as a spoiler if it contains your code.

Check your indenting.