Python - Compare two lists in a comprehension

Question

I\'m trying to understand how comprehensions work.

I would like to loop through two lists, and compare each to find differences. If one/or-more word(s) is different,

Answer 1

If you want to compare two lists for differences, I think you want to use a set.

s.symmetric_difference(t)   s ^ t   new set with elements in either s or t but not both

example:

>>> L1 = ['a', 'b', 'c', 'd']
>>> L2 = ['b', 'c', 'd', 'e'] 
>>> S1 = set(L1)
>>> S2 = set(L2)
>>> difference = list(S1.symmetric_difference(S2))
>>> print difference
['a', 'e']
>>> 

one-line form?

>>> print list(set(L1).symmetric_difference(set(L2)))
['a', 'e']
>>> 

if you really want to use a list comprehension:

>>> [word for word in L1 if word not in L2] + [word for word in L2 if word not in L1]
['a', 'e']

much less efficient as the size of the lists grow.