Question

Let say i have a string like this ‘this is a statement’
and if i want to search and replace string with this ‘this ** a statement’

string to search for this is a statement , this si a statement , this i a statement and any combination convert them into this trim a statement
i.e for any word combination between this & a statement replace it with trim
for another set replace fun to notfun .

so this is the program

import re
file=open('file','r+')
search=re.sub('this \(a_zA_Z0_9)+ a statement','\1trim',file),('this is fun','this is notfun',file)
file.close()

something is not right as nothing is getting changed in the file.

thanks everyone.

Answer 1

re.sub doesn’t work on files, it works on strings. You need to read the contents of the file into a string, then use re.sub to change the string, then write the modified string back to the file.

A simple example:

text = open("myfile.txt").read()
# This is your original re.sub call, but I'm not sure it really does what you want.
text = re.sub('this \(a_zA_Z0_9)+ a statement', '\1trim', text)
text = re.sub('this \(a_zA_Z0_9)+ another replacement', 'some other thing', text)
open("myfile.txt", "w").write(text)