what the hell is happening in that list comprehension? How is the range(a,b) constructed if a,b are defined in a child loop?

you can also just use {} braces instead of [] to directly create a set comprehension without the need of converting the list with set()

The best solution that I've seen so far

Try to not mutate the original array, create a new one and return that.

In other words,I should modify the elements of the array and return it.

You have to reduce that and only "WEST" should remain.

"NORTH", "SOUTH", "SOUTH", "EAST", "WEST", "NORTH", "WEST": array lengths differed, expected.length=1 actual.length=7
Can you please explain to me what is the meaning of this?

I have decoded , encoded and have passed some tests.Why is there such a mistake?
test.assert_equals(c.encode('\xe3\x82\xab\xe3\x82\xbf\xe3\x82\xab\xe3\x83\x8a'), '\xe3\x82\xbf\xe3\x83\xa2\xe3\x82\xbf\xe3\x83\xaf') File "/home/codewarrior/solution.py", line 27, in encode num=new_dict[self.key[i]]%26+new_dict[text[i]] KeyError: '\xe3'

ok,I going to try again.

Print the input to see what happens.

python

Which language?