Python Re.Sub Function Usage Issue

I need help with this re.sub function. For example, if I wanted to replace “string” with “abc” but I want #include <string.h> to remain the same so that the syntax does not get disturbed and all the other “string” variables get replaced with “abc”. How can I write the re.sub function?

The Python code is:

result = re.sub("string","abc", test_str, 0)

test_str is this

#include <string.h>
#include <stdlib.h>

char *Function(unsigned char *string, unsigned char *key)
{
unsigned int i, j;

for (i = 0; i < s(string); i++)
{
    
    string[i] = ~ string[i];
}

return string;
}

Answer

Use

result = re.sub(r"bstringb(?!.hb)", "abc", test_str)

See proof

Explanation

--------------------------------------------------------------------------------
  b                       the boundary between a word char (w) and
                           something that is not a word char
--------------------------------------------------------------------------------
  string                   'string'
--------------------------------------------------------------------------------
  b                       the boundary between a word char (w) and
                           something that is not a word char
--------------------------------------------------------------------------------
  (?!                      look ahead to see if there is not:
--------------------------------------------------------------------------------
    .                       '.'
--------------------------------------------------------------------------------
    h                        'h'
--------------------------------------------------------------------------------
    b                       the boundary between a word char (w)
                             and something that is not a word char
--------------------------------------------------------------------------------
  )                        end of look-ahead