Extracting string constant from source code in a string using regular expressions in Python

Question

How can I get a string constant from source code in a string?

For example, here is the source code I am trying to process:

var v = "this is string constant + some numbers and \" is also included "

I am unable to get everything inside quotation marks. by using this regular expression: "(.*?)".

I can't get var, v, = or anything else except string character.

Your question doesn't make much sense -- what exactly are you trying to accomplish? — tehsockz, Apr 14 '13 at 16:46
Looks like you're trying to parse some other programming language using Python. Don't do this using regular expressions; it will only lead to heartache. Use a proper parser. — kindall, Apr 14 '13 at 16:48
Possibly related: http://stackoverflow.com/questions/390992/javascript-parser-in-python — Aya, Apr 14 '13 at 16:51
@tehsockz I know that but I want to add this in my language. — Zeeshan Anjum, Apr 14 '13 at 16:55
@tehsockz I want to extract string constant in quotation marks — Zeeshan Anjum, Apr 14 '13 at 16:56
@Kindall thanks I did that for Identifiers, numbers, etc... but for String constant I don't know what to do the main problem is " in " " — Zeeshan Anjum, Apr 14 '13 at 16:59
Regex is a perfect fit for this. Language parsers are *built* using regular expressions, at least for parts of the job, and this is one. — Tim Pietzcker, Apr 14 '13 at 16:59
Could you provide a more clear example of what the desired output should be given the input string? — woemler, Apr 14 '13 at 17:01

score 1 · Answer 1 · answered Apr 14 '13 at 17:00

1

You need to match an opening quote, then anything that's either an escaped character or a normal character (except quotes and backslashes), and then a closing quote:

"(?:\\.|[^"\\])*"

answered Apr 14 '13 at 17:00

Tim Pietzcker

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Yes, was about to write that. There's a difference between _parsing_ a text completely and _extracting_ just some bits from it. – georg Apr 14 '13 at 17:02

score 1 · Accepted Answer · answered Apr 14 '13 at 17:26

Using lookbehind, to make sure the " is not preceded by a \

import re

data = 'var v = "this is string constant + some numbers and \" is also included "\r\nvar v = "and another \"line\" "'
matches = re.findall( r'= "(.*(?<!\\))"', data, re.I | re.M)
print(matches)

Output:

['this is string constant + some numbers and " is also included ', 'and another "line" ']

score 0 · Answer 3 · answered Apr 14 '13 at 17:11

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For get everything inside quotation marks you can try this: "\".+?\"" with re.findall()

answered Apr 14 '13 at 17:11

Navand

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Extracting string constant from source code in a string using regular expressions in Python

3 Answers3