import re
pattern = r"[0-9]\s*(?:[+-][+-]|\*/)\s*[0-9]"
strings = [
	'This is test 1 -- 1',
	'This is test 2',
	'This is test 3+1',
	'This is test 4 */4'
	]
	
for s in strings:
	res = re.search(pattern, s)
	if not res:
		print("Valid: " + s)