list comp.py

# so instead of doing this:
my_list = list()
for key in dictionary:
  if dictionary[key] == 'foo':
    my_list.append(key)

# you can use list comprehension to write code like this:
my_list = [key for key in dictionary if dictionary[key] == 'foo']

# both produce the same list of keys, but i think that using list comprehension is a lot more readable.