This one-liner is great, it lists the commands you have used by popularity. At present, the 'cd' command wins in my history file with 140. Followed by ls (93) and ssh (56). What are your top 3 commands

Snippet source: ibm

Builds and prints a list of all links in a specified webpage

Quick way to get the users home directory in Unix/Linux and Windows

Decompress a .tar.bz2 archive in Pytho

Computes the difference between two dates in seconds

Reads well formed RSS entries using standard python libraries

Reads a file line by line using Python in 3 lines

Very fast method for extracting all of the unique items from a list while preserving their original ordering.

Introduction
This function is a function that returns a function. You pass it a function, and it returns a function that takes a collection as a parameter and applies your function to it. The difference between this and map is that this returns a function that you can use again which takes a collection as a parameter.

For Example
If I had a collection c, and a function p that prints its argument, I can create a visitor function using the following:
printVisitor=createVisitor(p)

Then any time I want to print a collection I just type:
printVisitor(c)

A Better Example
If you were writing an IRC server you would probably have many functions that operated on a list of users, such as ban,makeop, etc. You could create those functions in a manor similar to the following:

banUsers=createVisitor(ban)
makeOperators=createVisitor(makeop)

Then in a seperate file you could use these functions as if they were regular functions.

you would type banUsers(users) to ban, or makeOperators(users) to promote those users.

Recursively removes files or directories with a given name, using find.

I most frequently use it to remove 'CVS' or '.svn' directories from sourcepackages that still have the versioning information in them.