Regex for managing escaped characters for items like string literals

Question

I would like to be able to match a string literal with the option of escaped quotations. For instance, I\'d like to be able to search \"this is a \'test with escaped\\\' val

Answer 1

If I understand what you're saying (and I'm not sure I do) you want to find the quoted string within your string ignoring escaped quotes. Is that right? If so, try this:

/(?

Basically:

• Start with a single quote that isn't preceded by a backslash;
• Match zero or more occurrences of: backslash then quote or any character other than a quote;
• End in a quote;
• Don't group the middle parentheses (the ?: operator); and
• The closing quote can't be preceded by a backslash.

Ok, I've tested this in Java (sorry that's more my schtick than Python but the principle is the same):

private final static String TESTS[] = {
        "'testing 123'",
        "'testing 123\\'",
        "'testing 123",
        "blah 'testing 123",
        "blah 'testing 123'",
        "blah 'testing 123' foo",
        "this 'is a \\' test'",
        "another \\' test 'testing \\' 123' \\' blah"
};

public static void main(String args[]) {
    Pattern p = Pattern.compile("(? %s%n", test, m.group(1));
        } else {
            System.out.printf("%s doesn't match%n", test);
        }
    }
}

results:

'testing 123' => testing 123
'testing 123\' doesn't match
'testing 123 doesn't match
blah 'testing 123 doesn't match
blah 'testing 123' => testing 123
blah 'testing 123' foo => testing 123
this 'is a \' test' => is a \' test
another \' test 'testing \' 123' \' blah => testing \' 123

which seems correct.