When I define a list and try to change a single item like this:

list_of_lists = [['a', 'a', 'a'], ['a', 'a', 'a'], ['a', 'a', 'a']]
list_of_lists[1][1] = 'b'
for row in list_of_lists:
    print row

It works as intended. But when I try to use list comprehension to create the list:

row = ['a' for range in xrange(3)]
list_of_lists = [row for range in xrange(3)]
list_of_lists[1][1] = 'b'
for row in list_of_lists:
    print row

It results in an entire column of items in the list being changed. Why is this? How can I achieve the desired effect with list comprehension?