I disagree with map/filter/reduce being "key" in Python. I've been writing Python for a long time and I never use them. Comprehensions are more pythonic than map+filter, and reduce just doesn't come up. Here's Guido explaining why he wanted to move all three functions out of builtins in Python 3:<p><a href="http://www.artima.com/weblogs/viewpost.jsp?thread=98196" rel="nofollow">http://www.artima.com/weblogs/viewpost.jsp?thread=98196</a>