python count number of unique elements in a list

# Basic syntax:
len(set(my_list))
# By definition, sets only contain unique elements, so when the list
# is converted to a set all duplicates are removed. 

# Example usage:
my_list = ['so', 'so', 'so', 'many', 'duplicated', 'words']
len(set(my_list))
--> 4

# Note, list(set(my_list)) is a useful way to return a list containing
#	only the unique elements in my_list

len(set(["word1", "word1", "word2", "word3"]))
# set is like a list but it removes duplicates
# len counts the number of things inside the set