How to correct unbalanced parenthesis error in regular expression?

Question

I am learning regular expression through Al Sweigart\'s automate the boring stuff course on udemy, lesson 29. I get an error saying \"unbalanced parenthesis at position 414 (lin

Answer 1

You need to fix this line (\d{2,5}))? # extension number part (optional). Clearly it needs to either add/remove a parenthesis.

Changing that line to (\d{2,5})? will fix the unbalanced parenthesis error.

Answer 2

Please note the unbalance that will probably give you an idea how to fix it.

     # Types of number 415-555-0000, 555-0000, (415) 555-0000, 555-0000 ext 12345,
     # ext. 12345, x12345
     (                             # (1 start)
          (                             # (2 start), area code (optional)
               ( \d\d\d )                    # (3)
            |  ( \( \d\d\d \) )              # (4)
          )?                            # (2 end)
          ( \s | - )                    # (5), first separator
          \d\d\d                        # first 3 digits
          -                             # separator
          \d\d\d\d                      # last 4 digits
          (                             # (6 start), extension word part (optional)
               (                             # (7 start)
                    ext
                    ( \. )?                       # (8)
                    \s
               )                             # (7 end)
            |  x
          )                             # (6 end)
          ( \d{2,5} )                   # (9), extension number part (optional)
     )?                            # (1 end)
=    )  <-- Unbalanced  ')'