how to remove c++ comments from a cpp file?

**Gary Herron** · Jan 26 '07, 09:15 AM

Re: how to remove c++ comments from a cpp file?

Frank Potter wrote:

I only want to remove the comments which begin with "//".
I did like this, but it doesn't work.
>
r=re.compile(ur "//[^\r\n]+$", re.UNICODE|re.V ERBOSE)
f=file.open("my cpp.cpp","r")
f=unicode(f,"ut f8")
r.sub(ur"",f)
>
Will somebody show me the right way?
Thanks~~
>
>

If you expect help with a problem, it would be nice if you told us what
the problem is. What error did you get?

But even without that I see lots of errors:

You must import re before you use it:
import re

Open a file with open((..) not file.open(...).

Once you open the file you must *read* the contents and operate on that:
data = f.read()

Then you ought to close the file:
f.close()

Now you can do your sub on the string in data -- but note, THIS WON'T
CHANGE data, but rather returns a new string which you must assign to
something:

new_data = r.sub(ur"", data)

Then do something with the new string.

Also I fear your regular expression is incorrect.

Cheers,
Gary Herron

**Frank Potter** · Jan 26 '07, 10:05 AM

Re: how to remove c++ comments from a cpp file?

On Jan 26, 5:08 pm, Gary Herron <gher...@island training.comwro te:

Frank Potter wrote:

I only want to remove the comments which begin with "//".
I did like this, but it doesn't work.

>

r=re.compile(ur "//[^\r\n]+$", re.UNICODE|re.V ERBOSE)
f=file.open("my cpp.cpp","r")
f=unicode(f,"ut f8")
r.sub(ur"",f)

>

Will somebody show me the right way?
Thanks~~If you expect help with a problem, it would be nice if you told us what

the problem is. What error did you get?
>
But even without that I see lots of errors:
>
You must import re before you use it:
import re
>
Open a file with open((..) not file.open(...).
>
Once you open the file you must *read* the contents and operate on that:
data = f.read()
>
Then you ought to close the file:
f.close()
>
Now you can do your sub on the string in data -- but note, THIS WON'T
CHANGE data, but rather returns a new string which you must assign to
something:
>
new_data = r.sub(ur"", data)
>
Then do something with the new string.
>
Also I fear your regular expression is incorrect.
>
Cheers,
Gary Herron

Thank you.
I'm very sorry because I was in a hurry when I post this thread.
I'll post again my code here:

Code:

import re

f=open("show_btchina.user.js","r").read()
f=unicode(f,"utf8")

r=re.compile(ur"//[^\r\n]+$", re.UNICODE|re.VERBOSE)
f_new=r.sub(ur"",f)

open("modified.js","w").write(f_new.encode("utf8"))

And, the problem is, it seems that only the last comment is removed.
How can I remove all of the comments, please?

**Gabriel Genellina** · Jan 26 '07, 10:45 AM

Re: how to remove c++ comments from a cpp file?

At Friday 26/1/2007 06:54, Frank Potter wrote:

>

Code:

>import re
>
>f=open("show_btchina.user.js","r").read()
>f=unicode(f,"utf8")
>
>r=re.compile(ur"//[^\r\n]+$", re.UNICODE|re.VERBOSE)
>f_new=r.sub(ur"",f)
>
>open("modified.js","w").write(f_new.encode("utf8"))
>

>
>And, the problem is, it seems that only the last comment is removed.
>How can I remove all of the comments, please?

Note that it's not as easy as simply deleting from // to end of line,
because those characters might be inside a string literal. But if you
can afford the risk, this is a simple way without re:

f = open("show_btch ina.user.js","r ")
modf = open("modified. js","w")
for line in f:
uline=unicode(l ine,"utf8")
idx = uline.find("//")
if idx==0:
continue
elif idx>0:
uline = uline[:idx]+'\n'
modf.write(ulin e.encode("utf8" ))
modf.close()
f.close()

--
Gabriel Genellina
Softlab SRL

_______________ _______________ _______________ _____
Preguntá. Respondé. Descubrí.
Todo lo que querías saber, y lo que ni imaginabas,
está en Yahoo! Respuestas (Beta).
¡Probalo ya!

Yahoo

http://www.yahoo.com.ar/respuestas

**Frank Potter** · Jan 26 '07, 11:15 AM

Re: how to remove c++ comments from a cpp file?

Thank you!

On Jan 26, 6:34 pm, Gabriel Genellina <gagsl...@yahoo .com.arwrote:

Code:

>[QUOTE]
f=open("show_btchina.user.js","r").read()
f=unicode(f,"utf8")
	
		
			
			
			
				At Friday 26/1/2007 06:54, Frank Potter wrote:
>
	
		
			
			
			
				
	Code:
	import re

			
		
	

			
		
	
>[QUOTE]
r=re.compile(ur"//[^\r\n]+$", re.UNICODE|re.VERBOSE)
f_new=r.sub(ur"",f)[/QUOTE]
>[QUOTE]
open("modified.js","w").write(f_new.encode("utf8"))
[/QUOTE]

>

And, the problem is, it seems that only the last comment is removed.
How can I remove all of the comments, please?Note that it's not as easy as simply deleting from // to end of line,

because those characters might be inside a string literal. But if you
can afford the risk, this is a simple way without re:
>
f = open("show_btch ina.user.js","r ")
modf = open("modified. js","w")
for line in f:
uline=unicode(l ine,"utf8")
idx = uline.find("//")
if idx==0:
continue
elif idx>0:
uline = uline[:idx]+'\n'
modf.write(ulin e.encode("utf8" ))
modf.close()
f.close()
>
--
Gabriel Genellina
Softlab SRL
>
_______________ _______________ _______________ _____
Preguntá. Respondé. Descubrí.
Todo lo que querías saber, y lo que ni imaginabas,
está en Yahoo! Respuestas (Beta).
¡Probalo ya!http://www.yahoo.com.ar/respuestas[/QUOTE]

**Laurent Rahuel** · Jan 26 '07, 03:35 PM

Re: how to remove c++ comments from a cpp file?

And using the codecs module

Code:

import codecs

f = codecs.open("show_btchina.user.js","r","utf-8")
modf = codecs.open("modified.js","w","utf-8")
for line in f:
idx = line.find(u"//")
if idx==0:
continue
elif idx>0:
line = line[:idx]+u'\n'
modf.write(line)
modf.close()
f.close()

Gabriel Genellina wrote:

At Friday 26/1/2007 06:54, Frank Potter wrote:
>

>>

Code:

>>import re
>>
>>f=open("show_btchina.user.js","r").read()
>>f=unicode(f,"utf8")
>>
>>r=re.compile(ur"//[^\r\n]+$", re.UNICODE|re.VERBOSE)
>>f_new=r.sub(ur"",f)
>>
>>open("modified.js","w").write(f_new.encode("utf8"))
>>

>>
>>And, the problem is, it seems that only the last comment is removed.
>>How can I remove all of the comments, please?

>
Note that it's not as easy as simply deleting from // to end of line,
because those characters might be inside a string literal. But if you
can afford the risk, this is a simple way without re:
>
f = open("show_btch ina.user.js","r ")
modf = open("modified. js","w")
for line in f:
uline=unicode(l ine,"utf8")
idx = uline.find("//")
if idx==0:
continue
elif idx>0:
uline = uline[:idx]+'\n'
modf.write(ulin e.encode("utf8" ))
modf.close()
f.close()
>
>

**Peter Otten** · Jan 26 '07, 03:45 PM

Re: how to remove c++ comments from a cpp file?

Laurent Rahuel wrote:

And using the codecs module

Why would you de/encode at all?

Peter

**Paul McGuire** · Jan 26 '07, 06:05 PM

Re: how to remove c++ comments from a cpp file?

On Jan 26, 3:54 am, "Frank Potter" <could....@gmai l.comwrote:

>
I'm very sorry because I was in a hurry when I post this thread.
I'll post again my code here:

Code:

import re
>
f=open("show_btchina.user.js","r").read()
f=unicode(f,"utf8")
>
r=re.compile(ur"//[^\r\n]+$", re.UNICODE|re.VERBOSE)
f_new=r.sub(ur"",f)
>
open("modified.js","w").write(f_new.encode("utf8"))

>

Here's a pyparsing version that will stay clear of '//' inside quoted
strings. (untested)

-- Paul

from pyparsing import javaStyleCommen t, dblQuotedString

f=open("show_bt china.user.js", "r").read()
f=unicode(f,"ut f8")

commentFilter = Suppress( javaStyleCommen t ).ignore( dblQuotedString )
f_new= commentFilter.t ransformString( f)

open("modified. js","w").write( f_new.encode("u tf8"))

**Gabriel Genellina** · Jan 27 '07, 02:55 AM

Re: how to remove c++ comments from a cpp file?

"Peter Otten" <__peter__@web. deescribió en el mensaje
news:epd751$518 $03$1@news.t-online.com...

Laurent Rahuel wrote:
>

>And using the codecs module

>
Why would you de/encode at all?

I'd say the otherwise: why not? This is the recommended practice: decode
inputs as soon as possible, work on Unicode, encode only when you write the
output.
In this particular case, it's not necesary and you get the same results,
only because these two conditions are met:

- the encoding used is utf-8
- we're looking for '//', and no unicode character contains '/' in its
representation using that encoding apart from '/' itself

Looking for the byte sequence '//' into data encoded with a different
encoding (like utf-16 or ucs-2) could give false positives. And looking for
other things (like '¡¡') on utf-8 could give false positives too.
The same applies if one wants to skip string literals looking for '"' and
'\\"'.
Anyway for a toy script like this, perhaps it does not make any sense at
all - but one should be aware of the potential problems.

--
Gabriel Genellina

**Toby** · Jan 27 '07, 04:55 PM

Re: how to remove c++ comments from a cpp file?

Frank Potter wrote:

r=re.compile(ur "//[^\r\n]+$", re.UNICODE|re.V ERBOSE)
f_new=r.sub(ur" ",f)

From the documentation:

re.MULTILINE
When specified [...] the pattern character "$" matches at the
end of the string and at the end of each line (immediately
preceding each newline). By default [...] "$" matches only at
the end of the string.

re.DOTALL
[...] without this flag, "." will match anything except a newline.

So a simple solution to your problem would be:

r = re.compile("//.*")
f_new = r.sub("", f)

Toby

how to remove c++ comments from a cpp file?

how to remove c++ comments from a cpp file?

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