question_marks.py

def QuestionsMarks(s):
  qnum = 0
  dig = 0
  has_10 = False
  for ch in s:
    if ch.isdigit():
      if int(ch) + dig == 10:
        if qnum != 3:
          return 'false'
        has_10 = True
      dig = int(ch)
      qnum = 0
    elif ch == '?':
      qnum += 1
  return 'true' if has_10 else 'false'

This code fails the following assertion:

assert(QuestionsMarks("7?6??3?4") == 'true')

If that is what was intended by the question, then I think the challenge question needs to be rewritten. The way I read the question, I thought that we needed to check every sub-string between any pair of numbers in the entire string that could add up to 10.

In fact, I just realized that the test case in the challenge

"5??aaaaaaaaaaaaaaaaaaa?5?a??5" == true

would be false under my reading of the question, so your code does seem to fit what the challenge had in mind, but I will stand by my assertion that the question is unclear.