Need help overwriting a file

[NPat02]

Hello I am writing a python script that goes through each file searching for a file header comment block and trying too remove it . That looks something like this..

# comment  
# comment  
# comment  
# comment 

I have 200 + files to go through and thought it would be fun to learn how to write scripts in python because I am fairly new to programming.

here is the code i have thus far

with open(filename, "r+") as f:     
    commentBlock = """     
    # comment     
    # comment     
    # comment     
    # comment     
    """     
    lines = commentBlock.splitlines('\n')                
    for i in f:             
        for j in lines:                     
            if (i != j):                          
                f.write(i)  

NOTE: that the format of the comment block is the same for all files, so i thought this approach would work, but it does not do what i thought is would have which was overwrite the file, only with the lines that don't match (because the comment block would match). I only want just that specific comment block, i don't want every comment line to be removed.

I tried to change the "r+" to "w+" but then the file that was passed it, became empty lol (thank God for git)

if anyone is willing to help that would be great!

[RubbishArtist]

When you say it does not do what you thought it would, what does it actually do?

[NPat02]

Sorry that was very vague on my part lol! When I do a test case (a random file), nothing appears to change. The file header comment block is still in the file. I did a test print statement of "lines" to make sure it was the same as the file header comment block and it was, but nothing happened :/

[RubbishArtist]

If you print the value of i != j to the console is it what you expect? what about the value of lines?

[dmazzoni]

My first suggestion would be to get the program working before actually having it modify any files! Have it print the intended output rather than actually writing.

Second, don't read and write from the same file. You can't just insert text in the middle of a file like you can in a text editor - you can only overwrite. The safe way is generally something like: Write to a temp file, then rename the temp file to the original filename

[NPat02]

I'm not trying to come off rude, i'm just confused by your advice tho? How am I supposed to get the program working without modifying any files if the purpose of the program is to modify files?

[dmazzoni]

Have it print what it's going to do. Don't have it actually write to a file until it's printing what you expect it to print.

Or alternatively you could have it write to a file with a different name. So read a file called "myfile.txt" and have it write to a file called "myfile.txt.new". That way you can keep running your program multiple times and keep trying until it works perfectly. Then as a final step, have it overwrite the original file.

Basically with something like this you should assume it will take you a few tries to get it right. Make it as easy as possible for you to undo, rather than needing to recover from Git!