Confused

Question

So the result of this is 4 despite it supposed to be 3. Confused as to why it's giving 4.

def lengthOfLongestSubstring(s):
Map = []
for char in s:
if char in Map:
pass
else:
Map.append(char)

return len(Map)
Map.clear()

print(lengthOfLongestSubstring('pwwkew'))

Answer 1

from pwkew pwke get appended to Map so len returns 4

instead of pass you should write Map=[] if you are expecting output 3

Answer 2

But I thought len() started at zero shoudn't it have been 3 anyway? Did it double count or something like that?

Answer 3

Length is always starting with one.

Answer 4

(my answer was not really the best...)