not able to replace string in a file using replace method

Question

Not able to replace the string in file

with open("dc_setup.tcl",'r+') as file:
        for line in file:
         if str0 in line:
            line1=line
            print(line1)
            contents=file.read()
            contents=contents.replace(line1,new_str)
            file.seek(0)
            file.truncate()
            file.write(contents)

I expect the code to replace string in that file , but I'm getting empty file

First, it is not known what is new_str. Second, if new_str is a valid string, you can check the contents by print(contents) first before & after the replacement. — amanb
– amanb, Commented Apr 29, 2019 at 9:49
print(contents) does not print anything before and after replacement . And , new_str is a valid string — Ganga
– Ganga, Commented Apr 29, 2019 at 10:17
If contents are not printed before replacement, then your file could be empty. Check the file contents and isolate the problem by reading the file separately and viewing the contents. — amanb
– amanb, Commented Apr 29, 2019 at 10:23

brunns · Accepted Answer · 2019-04-29 10:43:33Z

1

This section:

file.seek(0)
file.truncate()
file.write(contents)

Is overwriting the entire file, not just your current line. Editing text files in place is generally pretty hard, so the usual approach is to write to a new file. You can copy the new file back over the old file once you've finished if you like.

with open("dc_setup.tcl") as infile, open("new_dc_setup.tcl", "w") as outfile:
    for line in infile:
        if old_str in line:
            line = line.replace(old_str, new_str)
        outfile.write(line)

answered Apr 29, 2019 at 10:43

brunns

2,7641 gold badge15 silver badges25 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

not able to replace string in a file using replace method

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related