message: Update number-of-valid-words-in-a-sentence.py
diff: @@ -15,7 +15,7 @@ class Solution(object):
  token = hyphen = 0
  continue
  if sentence[i].isdigit() or \
  - (sentence[i] in '!.,' and not (i == len(sentence)-1 or sentence[i+1] == ' ')) or \
  + (sentence[i] in "!.," and not (i == len(sentence)-1 or sentence[i+1] == ' ')) or \
  (sentence[i] == '-' and not (hyphen == 0 and 0 < i < len(sentence)-1 and sentence[i-1].isalpha() and sentence[i+1].isalpha())):
  token = -1
  continue
  