Difference between set of strings doesn't work

Question

First of all thanks for the help, I'm trying to fix this problem for days.

File myStopWords.txt:

è
ad
più
a
b
c
17

My code:

stopWord = set(open("<...>/myStopwords.txt").read().split("\n"))
oldWords = set(["a","b","ad", "è", "più","17","horse"])

print( oldWords.difference(stopWord) )

Results:

{'horse', 'ad', 'più', 'è'}

Why aren't "ad" , "è" , "più" subtracted from the set ?

The result should be {horse} .

Answer 1

Thank you. As suggested in previous comments, this is the solution:

1) Convert the text file in UTF-8.

2)

fname = '<...>/myStopwords.txt'

with open(fname, encoding='utf-8') as f:
    content = f.readlines()

stopWord = [x.strip() for x in content] 


oldWords = set(["a","b","ad", "è", "più","17","horse"])
print( oldWords.difference(stopWord) )