Extracting multiple substring from a string

Question

I have a complicated string and would like to try to extract multiple substring from it.

The string consists of a set of items, separated by commas. Each item has an identifier (id-n) for a pair of words inside which is enclosed by brackets. I want to get only the word inside the bracket which has a number attached to its end (e.g. 'This-1'). The number actually indicates the position of how the words should be arrannged after extraction.

#Example of how the individual items would look like
id1(attr1, is-2) #The number 2 here indicates word 'is' should be in position 2
id2(attr2, This-1) #The number 1 here indicates word 'This' should be in position 1
id3(attr3, an-3) #The number 3 here indicates word 'an' should be in position 3
id4(attr4, example-4) #The number 4 here indicates word 'example' should be in position 4
id5(attr5, example-4) #This is a duplicate of the word 'example'

#Example of string - this is how the string with the items looks like
string = "id1(attr1, is-1), id2(attr2, This-2), id3(attr3, an-3), id4(attr4, example-4), id5(atttr5, example-4)"

#This is how the result should look after extraction
result = 'This is an example'

Is there an easier way to do this? Regex doesn't work for me.

I can't make sense of your example. Could you try describing it a different way? — DaoWen
– DaoWen, Commented Jun 12, 2013 at 4:00
@DaoWen - Sorry the string itself is a little complicated. It's difficult to describe it. — Cryssie
– Cryssie, Commented Jun 12, 2013 at 4:19
@IgnacioVazquez-Abrams - the number attached to the end of the second word in the brackets. — Cryssie
– Cryssie, Commented Jun 12, 2013 at 4:20

Burhan Khalid · Accepted Answer · 2013-06-12 04:43:00Z

2

A trivial/naive approach:

>>> z = [x.split(',')[1].strip().strip(')') for x in s.split('),')]
>>> d = defaultdict(list)
>>> for i in z:
...    b = i.split('-')
...    d[b[1]].append(b[0])
...
>>> ' '.join(' '.join(d[t]) for t in sorted(d.keys(), key=int))
'is This an example example'

You have duplicated positions for example in your sample string, which is why example is repeated in the code.

However, your sample is not matching your requirements either - but this results is as per your description. Words arranged as per their position indicators.

Now, if you want to get rid of duplicates:

>>> ' '.join(e for t in sorted(d.keys(), key=int) for e in set(d[t]))
'is This an example'

edited Jun 12, 2013 at 4:43

answered Jun 12, 2013 at 4:35

Burhan Khalid

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3 Comments

nhahtdh Over a year ago

example is repeated, though, which is not what OP wants.

Burhan Khalid Over a year ago

well if you want to be technical, his example isn't actually what he wants either since the words are switched around.

nhahtdh Over a year ago

I would take that as a typo. But the requirement about same position is stated quite clearly, though.

Dan Allan · Accepted Answer · 2013-06-12 04:50:07Z

2

Why not regex? This works.

In [44]: s = "id1(attr1, is-2), id2(attr2, This-1), id3(attr3, an-3), id4(attr4, example-4), id5(atttr5, example-4)"

In [45]: z = [(m.group(2), m.group(1)) for m in re.finditer(r'(\w+)-(\d+)\)', s)]

In [46]: [x for y, x in sorted(set(z))]
Out[46]: ['This', 'is', 'an', 'example']

edited Jun 12, 2013 at 4:50

answered Jun 12, 2013 at 4:29

Dan Allan

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2 Comments

nhahtdh Over a year ago

You failed to detect that example is repeated (same position of 4) and only one of them should be kept.

Dan Allan Over a year ago

OK, I have revised borrowing set from Burahn's answer.

Klaus-Dieter Warzecha · Accepted Answer · 2013-06-12 07:01:29Z

OK, how about this:

sample = "id1(attr1, is-2), id2(attr2, This-1), 
          id3(attr3, an-3), id4(attr4, example-4), id5(atttr5, example-4)"


def make_cryssie_happy(s):
    words = {} # we will use this dict later
    ll = s.split(',')[1::2]
    # we only want items like This-1, an-3, etc.

    for item in ll:
        tt = item.replace(')','').lstrip()
        (word, pos) = tt.split('-')
        words[pos] = word
        # there can only be one word at a particular position
        # using a dict with the numbers as positions keys 
        # is an alternative to using sets

    res = [words[i] for i in sorted(words)]
    # sort the keys, dicts are unsorted!
    # create a list of the values of the dict in sorted order

    return ' '.join(res)
    # return a nice string


print make_cryssie_happy(sample)

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