How to extract span in re.finditer method in python?

Question

the results of re.finditer is as below.

[i for i in result]
=[<re.Match object; span=(0, 10), match='sin theta '>,
 <re.Match object; span=(12, 18), match='cos x '>,
 <re.Match object; span=(20, 26), match='e ^ x '>,
 <re.Match object; span=(26, 32), match='f( x )'>,
 <re.Match object; span=(37, 45), match='log_ {x}'>]

Here, I used the code i.span instead of i, but I just got something as below.

[<function Match.span(group=0, /)>,
 <function Match.span(group=0, /)>,
 <function Match.span(group=0, /)>,
 <function Match.span(group=0, /)>,
 <function Match.span(group=0, /)>]

I'm gonna extract span in re.finditer. like (0,10), (12,18), ...

Help me please!

I defined the function for getting re.finditer The code is as below.

import re
def convert_ftn_to_token(seq):
    va = '[a-z]{1,}'

    ftn_lst = ['sin','cos','tan','log_', 'e ?\^'] 
    ftn_lst = [ftn + ' ?\{? ?' + va +' ?\}?' for ftn in ftn_lst]
    ftn_lst2  = [chr(i) for i in range(65,91)] + [chr(i) for i in range(97,123)]
    ftn_lst2 = [ftn + ' ?\( ?' + va + ' ?\)' for ftn in ftn_lst2]


    ftn_c = re.compile(
        '|'.join(ftn_lst2) +'|'+
        '|'.join(ftn_lst)
    )

    return re.finditer(ftn_c,seq)

i.span for i in results

Shorn · Answer 1 · 2023-02-16T09:03:13.753

0

You can use start() and end() in regex's Match object, documentation about it here. They correspond to the lower and upper bound of span respectively. As for the grouping stated in the docs, that only applies if you are intending to use the grouping functionality of Match. If you intend to get the span of the entire match, you can simply do match.start() and match.end(), where match is the match object returned by the regex.

Another option is using span() of the same Match object. Note this is different from just span which will give you the memory address rather than actually call the function. Doing match.span() will give you a tuple of the start and end. Taking your first match object as an example this would return (0,10)

edited Feb 16 '23 at 09:03

answered Feb 16 '23 at 08:58

Shorn

718
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Thanks for answer. but when I use start or end method, the result is `[, , , , ]` the same. – junsu lee Feb 16 '23 at 09:04
@junsulee **you need to call these methods**. You aren't calling them. – juanpa.arrivillaga Feb 16 '23 at 09:06
are you doing it with the brackets as `start()` or just `start`? Although slightly different from what I expect to see, it looks like the output is a function pointer rather than the function result which can occur if the function isn't invoked. You want to include the `()`. – Shorn Feb 16 '23 at 09:06

score 0 · Accepted Answer · answered Feb 16 '23 at 09:05

0

.span is a method, not an attribute. You want .span() which will give the start, end tuple.

answered Feb 16 '23 at 09:05

juanpa.arrivillaga

88,713
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It's also an attribute. – Kelly Bundy Feb 16 '23 at 09:57

How to extract span in re.finditer method in python?

2 Answers2