Problema con le RE....

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  • Alessandro
    #1

    Problema con le RE....

    Problema con le RE....
    Ho questa stringa "3 HOURS, 22 MINUTES, and 28 SECONDS" e la devo
    'dividere' nelle sue tre parti "3 HOURS", "22 MINUTES", "28 SECONDS".
    La cosa mi viene molto con le RE...(inutile la premessa che sono molto
    alle prime armi con RE e Python)
    Qesito perchè se eseguo questo codice
    [color=blue][color=green][color=darkred]
    >>>>regex=re.co mpile("[0-9]+ (HOUR|MINUTE|SE COND)")
    >>>>print regex.findall(" 22 MINUTE, 3 HOUR, AND 28 SECOND")[/color][/color][/color]
    ottengo come output:
    [color=blue][color=green][color=darkred]
    >>>> ['MINUTE', 'HOUR', 'SECOND'][/color][/color][/color]

    e non come mi aspettavo:
    [color=blue][color=green][color=darkred]
    >>>> ['3 MINUTE', '22 HOUR', '28 SECOND'][/color][/color][/color]

    Saluti e grazie mille...
    Alessandro

    Tags: None
    • Xavier Morel
      #2
      Re: Problema con le RE....

      Alessandro wrote:[color=blue]
      > Problema con le RE....
      > Ho questa stringa "3 HOURS, 22 MINUTES, and 28 SECONDS" e la devo
      > 'dividere' nelle sue tre parti "3 HOURS", "22 MINUTES", "28 SECONDS".
      > La cosa mi viene molto con le RE...(inutile la premessa che sono molto
      > alle prime armi con RE e Python)
      > Qesito perchè se eseguo questo codice
      > [color=green][color=darkred]
      > >>>>regex=re.co mpile("[0-9]+ (HOUR|MINUTE|SE COND)")
      > >>>>print regex.findall(" 22 MINUTE, 3 HOUR, AND 28 SECOND")[/color][/color]
      > ottengo come output:
      > [color=green][color=darkred]
      > >>>> ['MINUTE', 'HOUR', 'SECOND'][/color][/color]
      >
      > e non come mi aspettavo:
      > [color=green][color=darkred]
      > >>>> ['3 MINUTE', '22 HOUR', '28 SECOND'][/color][/color]
      >
      > Saluti e grazie mille...
      > Alessandro
      > [/color]
      Would probably be slightly easier had you written it in english, but
      basically the issue is the matching group.

      A match group is defined by the parenthesis in the regular expression,
      e.g. your match group is "(HOUR|MINUTE|S ECOND)", which means that only
      that will be returned by a findall.

      You need to include the number as well, and you can use a non-grouping
      match for the time (with (?: ) instead of () ) to prevent dirtying your
      matched groups.
      [color=blue][color=green][color=darkred]
      >>> pattern = re.compile(r"([0-9]+ (?:HOUR|MINUTE| SECOND))")[/color][/color][/color]

      Other improvements:
      * \d is a shortcut for "any digit" and is therefore equivalent to [0-9]
      yet slightly clearer.
      * You may use the re.I (or re.IGNORECASE) to match both lower and
      uppercase times
      * You can easily handle an optional "s"

      Improved regex:
      [color=blue][color=green][color=darkred]
      >>> pattern = re.compile(r"(\ d+ (?:hour|minute| second)s?)", re.I)
      >>> pattern.findall ("3 HOURS 22 MINUTES 28 SECONDS")[/color][/color][/color]
      ['3 HOURS', '22 MINUTES', '28 SECONDS'][color=blue][color=green][color=darkred]
      >>> pattern.findall ("1 HOUR 22 MINUTES 28 SECONDS")[/color][/color][/color]
      ['1 HOUR', '22 MINUTES', '28 SECONDS']

      If you want to learn more about regular expressions, I suggest you to
      browse and read http://regular-expressions.info/ it's a good source of
      informations, and use the Kodos software which is a quite good Python
      regex debugger.

        Comment

        • Alessandro
          #3
          Re: Problema con le RE....

          Thanks for the reply it's ok!!!
          The language? I selected the wrong newsgroup in my
          newsreader!!!.. .sorry...

          Thanks...

          Alessandro...

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