4. map

map is an iterable object that provides an extremely useful technique to apply a function on all elements of a list. For instance, I have found this very handy where in I want a bunch of consecutive Integers that represent a Year to be column indexes of a dataframe. What is happening here is that a range of consecutive integers starting from 2006 and ending at 2015, have all been converted into a list of strings, using map.

>>> list(map(str, range(2006, 2016)))
['2006', '2007', '2008', '2009', '2010', '2011', '2012', '2013', '2014', '2015']