How do I comment out lines without changing indentation?

Question

I use Vim to write my Python source and use the debugging library pdb.

Let's say I have this code with break points commented out:

import pdb

#pdb.set_trace()

def func1():
    #pdb.set_trace()
    foo_bar

I then want to globally un-comment all the pdb.set_trace() commands. Also, I'll want to re-comment them.

I figured out how to search for the commented string:

^\(\s*#\)\@!\s*pdb.set_trace() 

After this I don't know how to build a string of commands that would globally find the string and add a # to the beginning of the string so as not to mess up the indentation.

UPDATE:

I realized that I need to not re-comment lines with an existing # so I built upon the accepted answer:

To comment out:

:g/\s*\(#\)\@<!pdb.set_trace()/normal I#

Answer 1

Alternatively, you could use the :g command. I would do:

:g/\s*#pdb.set_trace()/normal ^x

to uncomment and

:g/\s*pdb.set_trace()/normal I#

to comment. This is nice because it's more readable (and shorter) than a search and replace command. Explanation:

:g/\s*#pdb.set_trace()/             "For every line matching this regex
                       normal       "Execute the following normal mode keystrokes:
                               ^x   "Go to first non-whitespace character and delete it.

The recommenting works the same, except it searches for a different string, and it uses I# instead of ^x. I# means insert # at the first non-whitespace column.

Answer 2

There is a solution which can be pretty simple if you are willing to use a plugin: NERDCommenter.

This plugin is made for "intensely orgasmic commenting" according to their github page. More precisely it creates several mappings to handle comments and one of the mappings is <Leader>ci which allows to toggle the comments of a line.

Combined to a global command it allows you do to what you can. Let's say your leader is , is can use the following command:

:g/pdb.set_trace()/normal ,ci

And that will toggle the comments on the lines matching pdb.set_trace()

Note that you cannot easily use <leader>directly in the normal command (see my question about that)

If your leader is <space> you'll have to do:

:g/pdb.Set_trace()/normal 1 ci

Note that it is easy to map it to a key:

nnoremap <key> :g/pdb.set_trace()/normal ,ci<CR>

And finally the big advantage of this method is that NERDcommenter handles automatically the language you are editing so you can create a command which will togle the comments on lines matching a defined pattern no matter what language you're editing:

command! -nargs=1 ToggleCom :execute "g/" . <f-args> . "/normal ,ci"

Now no matter which language you're editing you can use :ToogleCom foo to toggle the comment of all the lines matching foo. (If your leader is not , see the previous paragraph of my answer)

If you need different commenting styles you can change the mapping used, see :h NERDComFunctionalitySummary for more information.

Answer 3

You should be able to do a search and replace.

:%s/^\(\s*\)#\(\s*pdb.set_trace()\)/\1\2/

To un-comment and

:%s/^\(\s*\)\(pdb.set_trace()\)/\1#\2/

To re-comment.

This is done by using back-references. Anything matched in between memory parentheses \(\) can be recalled by using a back-reference (\1 and \2 in this case).

Edit: Oh, and I kind of forgot that you said you wanted this in a script. For using this in a script just omit the first colon. :)

Here's an example of using it in a function:

function! UncommentSetTrace()
   %s/^\(\s*\)#\(\s*pdb.set_trace()\)/\1\2/
endfunction

function! CommentSetTrace()
   %s/^\(\s*\)\(pdb.set_trace()\)/\1#\2/
endfunction

You should be able to just call this function and it will comment/uncomment all instances in your current file. If you want to use a single keystroke you can map it to the function:

noremap <A-c> :call CommentSetTrace()<CR>

This maps Alt+c to comment all the instances.