Regex: How to match sequence of key-value pairs at end of string

I am trying to match key-value pairs that appear at the end of (long) strings. The strings look like (I replaced the "\n")

my_str = "lots of blah
          key1: val1-words
          key2: val2-words
          key3: val3-words"

so I expect matches "key1: val1-words", "key2: val2-words" and "key3: val3-words".

The set of possible key names is known.
Not all possible keys appear in every string.
At least two keys appear in every string (if that makes it easier to match).
val-words can be several words.
key-value pairs should only be matched at the end of string.
I am using Python re module.

I was thinking

re.compile('(?:tag1|tag2|tag3):')

plus some look-ahead assertion stuff would be a solution. I can't get it right though. How do I do?

Thank you.

/David

Real example string:

my_str = u'ucourt métrage pour kino session volume 18\nThème: O sombres héros\nContraintes: sous titrés\nAuthor: nicoalabdou\nTags: wakatanka productions court métrage kino session humour cantat bertrand noir désir sombres héros mer medine marie trintignant femme droit des femmes nicoalabdou pute soumise\nPosted: 06 June 2009\nRating: 1.3\nVotes: 3'

EDIT:

Based on Mikel's solution I am now using the following:


my_tags = ['\S+'] # gets all tags
my_tags = ['Tags','Author','Posted'] # selected tags
regex = re.compile(r'''
    \n                     # all key-value pairs are on separate lines
    (                      # start group to return
       (?:{0}):            # placeholder for tags to detect '\S+' == all
        \s                 # the space between ':' and value
       .*                  # the value
    )                      # end group to return
    '''.format('|'.join(my_tags)), re.VERBOSE)

regex.sub('',my_str) # return my_str without matching key-vaue lines
regex.findall(my_str) # return matched key-value lines

The negative zero-width lookahead is (?!pattern).

It's mentioned part-way down the re module documentation page.

(?!...)

Matches if ... doesn’t match next. This is a negative lookahead assertion. For example, Isaac (?!Asimov) will match 'Isaac ' only if it’s not followed by 'Asimov'.

So you could use it to match any number of words after a key, but not a key using something like (?!\S+:)\S+.

And the complete code would look like this:

regex = re.compile(r'''
    [\S]+:                # a key (any word followed by a colon)
    (?:
    \s                    # then a space in between
        (?!\S+:)\S+       # then a value (any word not followed by a colon)
    )+                    # match multiple values if present
    ''', re.VERBOSE)

matches = regex.findall(my_str)

Which gives

['key1: val1-words ', 'key2: val2-words ', 'key3: val3-words']

If you print the key/values using:

for match in matches:
    print match

It will print:

key1: val1-words
key2: val2-words
key3: val3-words

Or using your updated example, it would print:

Thème: O sombres héros 
Contraintes: sous titrés 
Author: nicoalabdou 
Tags: wakatanka productions court métrage kino session humour cantat bertrand noir désir sombres héros mer medine marie trintignant femme droit des femmes nicoalabdou pute soumise 
Posted: 06 June 2009 
Rating: 1.3 
Votes: 3

You could turn each key/value pair into a dictionary using something like this:

pairs = dict([match.split(':', 1) for match in matches])

which would make it easier to look up only the keys (and values) you want.

More info:

来源：https://stackoverflow.com/questions/5323703/regex-how-to-match-sequence-of-key-value-pairs-at-end-of-string

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key-value