re.search not able to find the regex pattern inside a file

Question

I have test file(test.txt) as below:

`RANGE(vddout,sup)

`RANGE(vddin,sup_p) 

I would like to modify this file as below:

`RANGE(vddout,sup,tol_sup)

`RANGE(vddin,sup_p,tol_sup_p)

Here is the code I tried but its not able to find and the replace the pattern using re.search. Could you point out where is the flaw in the code?

 with open("test.txt", 'r+') as file :
    for line in file:
        print("line={}".format(line))
        findPattern=re.search(r'(`RANGE\(\w+,(\w+))\)',line)
        if findPattern:
            print("findPattern={}".format(findPattern))
            line=re.sub(r'(`RANGE\(\w+,(\w+))\)',r'\1,tol_\2',line)

Answer 1

As mentioned in the comments, you aren't writing the file.

Moreover, you are reading each line one by one when you could just be reading the entire file as a string to perform your manipulation. This is both inefficient (as you need to perform re.sub multiple times) and more complicated* to code (as you need to create a new string to write to the file).

Finally, you are performing re.match and re.sub. This is unnecessary as re.sub will simply do nothing if there is no match; you don't need to check first.

In [188]: with open('test.txt', 'r+') as f:
     ...:     data = f.read()
     ...:     updated = re.sub(r'(`RANGE\(\w+,(\w+))', r'\1,tol_\2', data)
     ...:     f.seek(0)         # Start writing at the beginning of the file
     ...:     f.write(updated)

*Note: more complex but not difficult