Delete lines containing a specific word

[Steven D'Aprano]

On Sun, 06 Jan 2008 09:21:33 -0800, Francesco Pietra wrote:

> Please, how to adapt the following script (to delete blank lines) to
> delete lines containing a specific word, or words?

That's tricky, because deleting lines from a file isn't a simple 
operation. No operating system I know of (Windows, Linux, OS X) has a 
"delete line" function.

Do you really need to delete the lines in place? It would be much simpler 
to leave the original data as-is, and create a new file with just the 
lines that aren't deleted.


> f=open("output.pdb", "r")
> for line in f:
> 	line=line.rstrip()
> 	if line:
> 		print line
> f.close()

How to adapt this script:

First, think about what this script does. That is, it goes through each 
line, and if the line is not blank, it prints it.

What do you want it to do instead? You want it to print the line if the 
line doesn't contain a specific word. So that's the first thing you need 
to change.

Secondly, you might want the script to write its output to a file, 
instead of printing. So, instead of the line "print line", you want it to 
write to a file.

Before you can write to a file, you need to open it. So you will need to 
open another file: you will have two files open, one for input and one 
for output. And you will need to close them both when you are finished.

Does that help you to adapt the script?


> If python in Linux accepts lines beginning with # as comment lines,
> please also a script to comment lines containing a specific word, or
> words, and back, to remove #.

The same process applies. Instead of "delete line", you want to "comment 
line". 



-- 
Steven