The Python equivalent of your JavaScript example is simply:

    def double(x): return x * 2

Python's `lambda` construct creates anonymous functions - its limitations mean it should only be used when anonymity is required. If a function is to be given a name, there is no reason to use a lambda over standard function syntax.

That won't work, you have to use something like partial instead if you want to use the operator module:

    from functools import partial
    import operator
    double = partial(operator.mul, 2)

And at that point I think it would way simpler to just define a normal function.

That don't work since you need to use `partial` on `mul`.

I'm a big fan of the way Haskell manages operators and partial application.

    double :: Num a => a -> a
    double = (2 *)