import re
theString = "abcABC"
pattern = re.compile(r"(?<![A-Z])[A-Z]{3}(?![A-Z])")
result = pattern.search(theString)
print("Matched string: " + result.group())
aW1wb3J0IHJlCnRoZVN0cmluZyA9ICJhYmNBQkMiCnBhdHRlcm4gPSByZS5jb21waWxlKHIiKD88IVtBLVpdKVtBLVpdezN9KD8hW0EtWl0pIikKcmVzdWx0ID0gcGF0dGVybi5zZWFyY2godGhlU3RyaW5nKQoKcHJpbnQoIk1hdGNoZWQgc3RyaW5nOiAiICsgcmVzdWx0Lmdyb3VwKCkp