Sorting

Every Python list has a sort method that sorts it in place. If you don’t want to mess up your list, you can use the sorted function, which returns a new list:

x = [4, 1, 2, 3]
y = sorted(x)     # is [1, 2, 3, 4], x is unchanged
x.sort()          # now x is [1, 2, 3, 4]

By default, sort (and sorted) sort a list from smallest to largest based on naively comparing the elements to one another.

If you want elements sorted from largest to smallest, you can specify a reverse=True parameter. And instead of comparing the elements themselves, you can compare the results of a function that you specify with key:

# sort the list by absolute value from largest to smallest
x = sorted([-4, 1, -2, 3], key=abs, reverse=True)  # is [-4, 3, -2, 1]

# sort the words and counts from highest count to lowest
wc = sorted(word_counts.items(),
          key=lambda (word, count): count,
          reverse=True)