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Python Regular Expressions in Python Introduction to Regular Expressions Players Dictionary and Class

Posted by Alexander Davison
Alexander Davison
65,469 Points

"Bummer! `players` doesn't seem to be a regex object". Hunh?

What's wrong with this code? Is it related to something with the regex string or is it related to my function call? Please explain :)

Any help appreciated.

Thanks, Alex

players.py 
import re

string = '''Love, Kenneth: 20
Chalkley, Andrew: 25
McFarland, Dave: 10
Kesten, Joy: 22
Stewart Pinchback, Pinckney Benton: 18'''

players = re.match(r'''
    (?P<last_name>[a-zA-Z]+),\s
    (?P<first_name>[a-z-A-Z]):\s
    (?P<score>\d+)
''', string, re.MULTILINE)

Tagging Chris Freeman

1 Answer

Chris Freeman
MOD
Chris Freeman
Treehouse Moderator 68,423 Points
Chris Freeman
Chris Freeman
Treehouse Moderator 68,423 Points

When the match isn't found, a None is returned which results in the error seen.

There are some errors in the regex:

  • to use the plus sign signifying "one or more", you need to wrap the set of characters in parens. Do this for both the first and last name sets.
  • since one of the first and last names includes a space, add a \s in the character set
  • add the switch re.VERBOSE to ignore the extra white space in the regex. Remember to include a pipe symbol between the re switches.
  • include a start-of-line anchor ^ at the start of the pattern to align properly for the multiline matching
Alexander Davison
Alexander Davison
65,469 Points

It is still producing the same error, sadly.

Here's my code:

import re

string = '''Love, Kenneth: 20
Chalkley, Andrew: 25
McFarland, Dave: 10
Kesten, Joy: 22
Stewart Pinchback, Pinckney Benton: 18'''

players = re.match(r'''
    (?P<last_name^(a-zA-Z)+),\s
    (?P<first_name>^(a-z-A-Z)+):\s
    (?P<score>^\d+)
''', string, re.MULTILINE|re.VERBOSE)
Chris Freeman
Chris Freeman
Treehouse Moderator 68,423 Points
Chris Freeman
Chris Freeman
Treehouse Moderator 68,423 Points

Sorry. I was misleading about the parens and the plus sign. You can use the plus sign also on a square bracket character set as in you original code for last_name. A plus is also needed in the same manner on the first_name.

  • Still need a \s added into the first_name and last_name character sets.
  • when matching on a hyphen it is usually best to put it as the first character in the set so it isn't confused with a character range.
  • only a single caret ^ is needed in front of the first group paren.

Here is one solution:

players = re.match(r'''
    ^(?P<last_name>[a-z\sA-Z]+),\s
    (?P<first_name>[-a-z\sA-Z]+):\s
    (?P<score>\d+)
''', string, re.MULTILINE|re.VERBOSE)
Alexander Davison
Alexander Davison
65,469 Points

Thank you! I understand now.

However, I'm still confused on the ^ and why you need it... What's it for?

Chris Freeman
Chris Freeman
Treehouse Moderator 68,423 Points
Chris Freeman
Chris Freeman
Treehouse Moderator 68,423 Points

The caret ^ matches the beginning of the line or each line start in re.MULILINE. More at docs

Alexander Davison
Alexander Davison
65,469 Points

Thanks!