CODEWITHSUNDEEP
pythonregexpython-3.xfile
sanforyou
sanforyou

Reputation: 455

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

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)

Upvotes: 5

Views: 172

Answers (2)

aydow
aydow

Reputation: 3801

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

Upvotes: 2

Krishna
Krishna

Reputation: 1362

This should work. (you don't have to search first and then replace. You can directly attempt to replace. It only replaces if it matches in the first place)

import re

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

Upvotes: 2

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