why is the phone_pattern getting matched but phone_patt isnt??i think \1 refers to group 1...am i wrong??

Question

import re
no = "345-678-091"
phone_pattern = re.compile('\d{3}-\d{3}-\d{3}')
phone_patt = re.compile("(\d{3})-\1-\1")
print(phone_pattern.search(no))
print(phone_patt.search(no))

Answer 1

"(\d{3})-\1-\1" will match if it finds three digits followed by a hyphen and then the same three digits again, a hyphen and the same three digits again.

It won't match 345-678-091 but it would match 345-345-345.