Qfyilyi

I need to find the following from c code using regular expression python but some how i could not write it properly.

if(condition)

     /*~T*/

     {

        /*~T*/

        _getmethis = FALSE;

     /*~T*/

     }

..........

/*~T*/

     _findmethis = FALSE;

......

                    /*~T*/

_findthat = True;

I need to find all variables after /*~T/ starting with underscore and write to new file but my code could not find it i tried several regex pattern it is always empty output file

import re

fh = open('filename.c', "r")

output = open("output.txt", "w")

pattern = re.compile(r'(/*~T*/)(s*?ns*)(_[aA-zZ]*)')

for line in fh:

for m in re.finditer(pattern, line):

    output.write(m.group(3))

    output.write("n")



output.close()

The reason you do not find anything is that your pattern crosses multiple lines but you are only looking at your file one line at a time.

Consider using this:

t = """

if(condition)

     /*~-*/

     {

        /*~T*/

        _getmethis = FALSE;

     /*~-*/

     }

..........

/*~T*/

     _findmethis = FALSE;



     /*~T*/

     do_not_findme_this = FALSE;

"""



import re

pattern = re.compile(r'/*~T*/.*?ns+(_[aA-zZ]*)', re.MULTILINE|re.DOTALL)

for m in re.finditer(pattern, t):  # use the whole file here - not line-wise

    print(m.group(1))

The pattern uses 2 flags that tell regex to use multiline matches and that dots . also match newlines (by default they don't) together with a non greedy .*? to make the gap between /*~-T*/ and the following group minimal large.

Printout:

_getmethis

_findmethis

Doku:

• re.MULTILINE


• re.DOTALL

You need to read the file in as a whole with fh.read() and make sure you amend the pattern to only match letters since [aA-zZ] matches more than just letters.

The pattern I suggest is

(/*~T*/)([^Sn]*ns*)(_[a-zA-Z]*)

See the regex demo. Note that I deliberately subtracted n from the first s* to make matching more efficient.

When reading files in, it is more convenient to use with so that you do not have to use .close():

import re

pattern = re.compile(r'(/*~T*/)(s*?ns*)(_[aA-zZ]*)')



with open('filename.c', "r") as fh:

    contents = fh.read()

    with open("output.txt", "w") as output:

        output.write("n".join([x.group(3) for x in pattern.finditer(contents)]))