Python only replace string which is not C++ comment

Question

I want to deal only with string which is NOT C++ comment, here is the pattern to find out C++ comment:

pattern = re.compile(r'//.*?$|/\*.*?\*/|\'(?:\\.|[^\\\'])*\'|"(?:\\.|[^\\"])*"', re.DOTALL | re.MULTILINE)

However, I don't know how to make it to work as my intention.

# Python 3.4.2
s = '''
/****
C++ comments
  //pResMgr->CreateDialogEx();
****/
//pResMgr->CreateDialogEx();
/*//pResMgr->CreateDialogEx();*/

// real code, I want to replace only this following line of code
pResMgr->CreateDialogEx();
'''

newS = s.replace('CreateDialogEx', 'Create')
print(newS)

My expected output is:

/****
C++ comments
  //pResMgr->CreateDialogEx();
****/
//pResMgr->CreateDialogEx();
/*//pResMgr->CreateDialogEx();*/

// real code, I want to replace only this following line of code
pResMgr->Create();

I would not use regex if I were you, I think you'd better iterate over your string removing what is after // until new line and what is after /* until */... and THEN apply regex... — n00dl3
– n00dl3, Commented Jul 13, 2015 at 7:31
@JuniusRendel , how about pResMgr->CreateDialogEx(); // pResMgr->CreateDialogEx();? — O'Skywalker
– O'Skywalker, Commented Jul 13, 2015 at 7:43
@JuniusRendel, pResMgr->CreateDialogEx(); // pResMgr->CreateDialogEx(), as in your advice, I can delete comments at first, it's true, but my result should contain the original unchanged comment. What's the time to add deleted text? — O'Skywalker
– O'Skywalker, Commented Jul 13, 2015 at 8:00
Possible duplicate with stackoverflow.com/questions/16720541/…. — Eenoku
– Eenoku, Commented Jul 13, 2015 at 8:08

Martin Gottweis · Accepted Answer · 2015-07-13 11:08:14Z

2

Didn't test it, but it works it with your case and fundamentally should work. It basically goes throught the text finding newline, // or /* and then handling the cases. Really simple, no regex.

source_code = '''//pResMgr//->CreateDialogEx();'''

def indexOf(string, character):
    return string.index(character) if character in string else 9999999

def replaceNotInComments(string, searchFor, replaceWith):
    result = ''
    nextBreak = 0
    while True:
        nextBreak = min(indexOf(string, '\n'),
                        indexOf(string, '/*'),
                        indexOf(string, '//'))
        if nextBreak == 9999999:
            result += string.replace(searchFor, replaceWith);
            break
        result += string[0:nextBreak].replace(searchFor, replaceWith);

        if nextBreak == indexOf(string, '\n'):
            string = string[nextBreak+1:]

        if nextBreak == indexOf(string, '/*'):
            string = string[nextBreak+2:]
            result += '/*'+string[0:indexOf(string, '*/')+2]
            string = string[indexOf(string, '*/')+2:]

        if nextBreak == indexOf(string, '//'):
            string = string[nextBreak+2:]
            if result != '':
                result += '\n'  
            result += string[0:indexOf(string, '\n')+1]
            string = string[indexOf(string, '\n')+1:]


    return result

result = replaceNotInComments(source_code, 'CreateDialogEx', 'Create')
print(result)

edited Jul 13, 2015 at 11:08

answered Jul 13, 2015 at 8:10

Martin Gottweis

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6 Comments

O'Skywalker Over a year ago

your result changes '/' to '\'! here is your result: \ **** C++ comments //pResMgr->CreateDialogEx(); ****/ pResMgr->CreateDialogEx(); \ *//pResMgr->CreateDialogEx();*/ // real code, I want to replace only this following line of code pResMgr->Create();

Martin Gottweis Over a year ago

oh, that was a typo. Works now?

O'Skywalker Over a year ago

I found a serious issue, if source_code = '''//pResMgr->CreateDialogEx();''', your code still changes source_code

Martin Gottweis Over a year ago

fixed again. btw, you can try to debug the code yourself

O'Skywalker Over a year ago

ouch, I found another bug, suppose input: source_code = 'cout << "hello, money\r\n, new line;"', then output lost '\r\n', it becomes 'cout << "hello, money , new line;"', how can I change your code directly?

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