Parse items from text file

Question

I have a text file that includes data inside {[]} tags. What would be the suggested way to parse that data so I can just use the data inside the tags?

Example text file would look like this:

'this is a bunch of text that is not {[really]} useful in any {[way]}. I need to {[get]} some items {[from]} it.'

I would like to end up with 'really', 'way', 'get', 'from' in a list. I guess I could use split to do it.. but seems like there might be a better way out there. I have seen a ton parsing libraries, is there one that would be perfect for what I want to do?

Answer 1

I would use regular expressions. This answer assumes that none of the tag characters {}[] appear within other tag characters.

import re
text = 'this is a bunch of text that is not {[really]} useful in any {[way]}. I need to {[get]} some items {[from]} it.'

for s in re.findall(r'\{\[(.*?)\]\}', text):
    print s

Using the verbose mode in python regular expressions:

re.findall('''
    \{   # opening curly brace
    \[   # followed by an opening square bracket
    (    # capture the next pattern
    .*?  # followed by shortest possible sequence of anything
    )    # end of capture
    \]   # followed by closing square bracket
    \}   # followed by a closing curly brace
    ''', text, re.VERBOSE)

Answer 2

This is a job for regex:

>>> import re
>>> text = 'this is a bunch of text that is not {[really]} useful in any {[way]}. I need to {[get]} some items {[from]} it.'
>>> re.findall(r'\{\[(\w+)\]\}', text)
['really', 'way', 'get', 'from']

Answer 3

slower, bigger, no regular expresions

the old school way :P

def f(s):
    result = []
    tmp = ''
    for c in s:
        if c in '{[':
            stack.append(c)
        elif c in ']}':
            stack.pop()
            if c == ']':
                result.append(tmp)
                tmp = ''
        elif stack and stack[-1] == '[':
            tmp += c
    return result

>>> s
'this is a bunch of text that is not {[really]} useful in any {[way]}. I need to {[get]} some items {[from]} it.'
>>> f(s)
['really', 'way', 'get', 'from']

Answer 4

Another way

def between_strings(source, start='{[', end=']}'):
    words = []
    while True:
        start_index = source.find(start)
        if start_index == -1:
            break
        end_index = source.find(end)
        words.append(source[start_index+len(start):end_index])
        source = source[end_index+len(end):]
    return words


text = "this is a bunch of text that is not {[really]} useful in any {[way]}. I need to {[get]} some items {[from]} it."
assert between_strings(text) == ['really', 'way', 'get', 'from']