Well, for one I believe they pre-date comprehensions. Having them as functions is also occasionally useful for partial application, e.g.

  from functools import partial
  to_strings = partial(map, str)
  # vs
  def to_strings(seq):
      return (str(elem) for elem in seq)

I can see it together with partial, yes, that's when it can become a bit cleaner. Another reason why I use map is when I want to use multiprocessing or multithreading (with IO heavy functions). But on a fine grained level of code I find it really hurts readability compared to comprehensions.

Or this:

    def to_strings(seq):
        return map(str, seq)

Generally, when the operation I'm applying to each element happens to already be a named function, I find "map(f, seq)" preferable to "(f(x) for x in seq)".

Coming from Ruby it's easier to use map, because it's what Ruby's standard library offers.

However comprehensions are not that harder when one finally decides to understand how they work. Not as readable as map() IMHO. Example:

Ruby

    [1, 2, 3].map {|x| x*x} # object.method(args)

vs Python

    [x*x for x in [1, 2, 3]]

where we have the function first, then the definition of the variable, then the data. This is the opposite of the object.method OO notation and using a variable before defining it is not what we usually do. But it's almost the usual mathematical notation "for i in set do f(i)" with the function at the beginning.

Not a big deal.

About a problem raised in a comment of the post (which is from 2009): this is Guido (2009) about the lack of tail call optimization in Python http://neopythonic.blogspot.it/2009/04/tail-recursion-elimin...

In my experience filter/map are used by people who just don't know about comprehensions, or are not used to having them available. It takes some time to start using them where properly.