Why does Python not look at the whole strings(sorted)?

Question

I am trying to solve the google python class exercises. But i am kinda stuck on this one because i dont know why python looks at the characters themselfs and not at the whole string. Can someone tell me why Python looks at the characters and not the strings?

# B. front_x
# Given a list of strings, return a list with the strings
# in sorted order, except group all the strings that begin with 'x' first.
# e.g. ['mix', 'xyz', 'apple', 'xanadu', 'aardvark'] yields
# ['xanadu', 'xyz', 'aardvark', 'apple', 'mix']
# Hint: this can be done by making 2 lists and sorting each of them
# before combining them.
def front_x(words):
for word in words:
if word[0:1] == "x":
Liste = []
Liste += word
else:
Liste2 = []
Liste2 += word

return sorted(Liste) + sorted(Liste2)
words = ['mix', 'xyz', 'apple', 'xanadu', 'aardvark']
print(front_x(words))

output :
['a', 'a', 'd', 'n', 'u', 'x', 'a', 'a', 'a', 'd', 'k', 'r', 'r', 'v']

Answer 1

Try this:
Liste.append(word)
And:
Liste2.append(word)
Where you use +=

Answer 2

A string is just an array of characters if you think about it. So `Liste = []` will make an empty array and `Liste += word` will add the two arrays together.
It's quirky but it is what it is. What you probably want to do is `Liste.append(word)`.
I can see another mistake in your code but I hope this brings you a step further :P