How to comment out a block of code in Python

Question

Is there a mechanism to comment out large blocks of Python code?

Right now, the only ways I can see of commenting out code are to either start every line with a #, or to enclose the code in triple quotes: """.

The problem with these is that inserting # before every line is cumbersome and """ makes the string I want to use as a comment show up in generated documentation.

After reading all comments, the answer seems to be "No".

This question was answered previously in Stack Overflow question *[Why doesn't Python have multiline comments?](http://stackoverflow.com/questions/397148)*. — ChristopheD, Mar 23 '09 at 22:26
Additional guidelines of professional practice, "Don't use triple-quotes", distinguishes it from other posts ... — AjayKumarBasuthkar, Jan 07 '15 at 22:23
Sigh. One more useful and non-duplicate question marked as duplicate... This one asks for a solution, while the other one takes the answer (namely that no, there's no solution) as a prerequisite for asking what it has to ask. — Helen, Apr 08 '19 at 15:53
Perl allows you to use the documentation syntax for block commenting in such a way that it does NOT end up in the documentation. That's why we have more than one way to do things. It's called 'flexibility'. <\snark> — mpersico, Apr 29 '20 at 20:10
For Jupyter, to comment use `Crtl + /` and uncomment use `Crtl - /` — circassia_ai, Feb 15 '21 at 13:55

score 481 · Accepted Answer · edited Oct 13 '21 at 19:52

481

Python does not have such a mechanism. Prepend a # to each line to block comment. For more information see PEP 8. Most Python IDEs support a mechanism to do the block-commenting-with-hash-signs automatically for you. For example, in IDLE on my machine, it's Alt+3 and Alt+4.

Don't use triple-quotes; as you discovered, this is for documentation strings not block comments, although it has a similar effect. If you're just commenting things out temporarily, this is fine as a temporary measure.

edited Oct 13 '21 at 19:52

NerdOnTour

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answered Mar 23 '09 at 22:20

John Feminella

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Geany also has this. Right click, Format, Comment Line(s). – NoBugs Oct 27 '11 at 02:06
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For non-Americans, that's a "hash" sign. – edam Oct 31 '11 at 14:36
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in **Notepad++** that's `Ctrl+K` (v.5.9.2) for any supported language – Janusz Lenar Dec 03 '11 at 00:50
1

In Eclipse, toggling comment for a selected block of code is performed using Ctrl+/. You do not need to select the code if it is only a single line. – lightalchemist Jun 06 '12 at 06:58
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Even for Americans, "pound" should be £ or ₤. – glglgl Jul 04 '12 at 16:12
one disadvantage of mix multi-line string and block comments is IDE has no idea what you want thus can't show comment in different style as needed. – Baiyan Huang Sep 17 '12 at 03:58
1

In **Vim** with [NERDCommentor](http://www.vim.org/scripts/script.php?script_id=1218) installed, it is as easy as selecting the portion of code to be commented and pressing `\c` – Santosh Kumar Sep 29 '12 at 15:44
In PyCharm, it's CTRL-/ – sparc_spread Feb 20 '13 at 16:38
You can't triple-quote code that contains triple-quotes. – Keith Thompson Jun 26 '13 at 22:18
70

Actually, that symbol is called an octothorp. Please stop using local slang terms - few Americans call it a hash, and few non-Americans call it a pound, but nobody ever refers to anything else when they say octothorp. Except the person who chooses to defy this definitive answer by using it to mean something else. – ArtOfWarfare Jul 23 '13 at 14:33
10

The creator of python actually [suggests to use multi-line strings as block comments](http://stackoverflow.com/a/7696966/346561), so I would say your statement "Don't use triple-quotes" isn't appropriate. – Jesse Webb Oct 30 '13 at 19:19
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@JesseWebb: He wrote that about two and a half years after this answer, though, so he changed his mind. :) – John Feminella Nov 01 '13 at 15:05
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From a Microsoft developer, # is a "sharp" sign – BufBills Dec 20 '13 at 22:04
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@JesseWebb Although it might be noted to use triple quotes, I found a bug in python library I was using (Pyshark) with regards to Python 3. there used to be this line in a triple quote comment in the pyshark library: (i.e. \Device\NPF_..). This was ignored in Python2 and ran fine, but Python 3 threw this error: "SyntaxError: (unicode error) 'unicodeescape' codec can't decode bytes in position 14-15: malformed \N character." Since then, I avoid triple quotes. – continuousqa Sep 23 '14 at 17:39
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`Ctrl+/` in **PyCharm** will do comment / uncomment the highlighted rows – shreyansp Sep 11 '15 at 08:06
As said above, Python's creator actually suggests using triple quotes as block comments. Most editors will detect a triple-quoted string used in this way (not assigned or used in any way) and color it with the comment color. You can use `'''` to comment blocks of code containing `"""` and vice-versa. – Tobia Mar 23 '17 at 12:11
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Calling it a hash, hash symbol, or number sign is the best bet. Especially now in 2017 hash is one of the most common ways to refer to that symbol. Nobody refers to it as an octothorpe except people trying to show off that they know that it's called an octothorpe. https://www.oxfordlearnersdictionaries.com/us/definition/english/hash_1?q=hash – Caboose Nov 01 '17 at 20:59
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It's a sharp sign for musicians.(e.g A major scale: A B C# D E F# G# A) – Nirvan Nov 18 '17 at 20:55
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@johnktejik This '♯' is a sharp sign. '#' this is the number sig. – szpanczyk Mar 13 '18 at 12:38
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The correct term is 'number sign' (Unicode U+0023). It is also indexed under 'octothorpe', 'crosshatch', 'pound sign', and 'hash'. – Urhixidur May 09 '18 at 13:33
2

`few Americans call it a hash, and few non-Americans call it a pound` The number of Americans that call it a hash plus the number of non-Americans that call it a pound is at least 1,000 times the number of people on Earth that call it octothorpe. – Joe Oct 15 '21 at 14:24
And here this whole time I thought it was called a comment-symbol – emery Oct 18 '21 at 17:07

score 101 · Answer 2 · answered Mar 24 '09 at 00:47

101

Hide the triple quotes in a context that won't be mistaken for a docstring, eg:

'''
...statements...
''' and None

or:

if False: '''
...statements...
'''

answered Mar 24 '09 at 00:47

bobince

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I don't think that is a good advice, you are adding complexity to your code without any real benefit. Someone reading that would have to figure out why is that code there and what is it suppouse to do. – Facundo Casco May 25 '12 at 15:49
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What if the code you want to comment out already contains triple-quoted strings? – Keith Thompson Jun 26 '13 at 22:19
1

luckily for me it did not. – Zack Oct 29 '13 at 18:24
1

@keithThompson then use the other kind of triple quoted string – Leo Jun 16 '21 at 00:57

score 99 · Answer 3 · answered Mar 23 '09 at 22:22

99

The only cure I know for this is a good editor. Sorry.

answered Mar 23 '09 at 22:22

canen

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Clearly, all Real Python Programmers use ed, where this problem is easily solved with: 12,31s/^/#/ – John Fouhy Mar 23 '09 at 23:49
3

vim with nerdcommenter. Select the block you want and ,c – dev_nut Oct 10 '14 at 22:37

score 48 · Answer 4 · edited Mar 19 '14 at 05:53

48

The only way you can do this without triple quotes is to add an:

if False:

And then indent all your code. Note that the code will still need to have proper syntax.

Many Python IDEs can add # for you on each selected line, and remove them when un-commenting too. Likewise, if you use vi or Emacs you can create a macro to do this for you for a block of code.

edited Mar 19 '14 at 05:53

Peter Mortensen

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answered Mar 23 '09 at 22:19

Brian R. Bondy

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The op mentioned that they do not want the comments to appear as doc strings. – Ed S. Mar 23 '09 at 22:22
-1 retracted. That's a clever idea, though it may mean that the comments need comments :) – Ed S. Mar 23 '09 at 22:49
3

That solution is similar to just commenting out the code, except that you add four spaces instead of # and that you also need to add "if False:" line. – Yoo Sep 23 '09 at 08:21
1

I was doing some script hacking and that is what I came up with. (So, +1). It's very slick that I can simply write "if False:", push the block over 1 tab and I'm done. I've used more than one editor where the method is nothing more than,highlight the block, then press tab. Strangely enough, I asked the original question for a friend, wanting to show off S.O. back when it was new. – gbarry Mar 31 '18 at 04:55
2

Ctrl+ / or Ctrl + Shift+/ in PyCharm does the same – Kazem Mar 24 '19 at 02:58

score 43 · Answer 5 · edited Oct 01 '13 at 15:04

43

In JetBrains PyCharm on Mac use Command + / to comment/uncomment selected block of code. On Windows, use CTRL + /.

edited Oct 01 '13 at 15:04

Mark Richman

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answered Mar 04 '13 at 07:35

marcinj

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This also works for PyCharm Community Edition, which is free and open-sourced. – Arda Aug 27 '14 at 12:26
thanks! works with text wrangler as well – suyash gautam Sep 23 '16 at 03:46
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`CTRL`+`/` on Windows doesn't work for a Swedish keyboard layout. – HelloGoodbye Aug 22 '17 at 08:16
Also works for VSCode on macOS – Hang Chen Nov 29 '22 at 01:57
Also works on VSCode on Windows – Marja van der Wind Feb 09 '23 at 19:27

score 29 · Answer 6 · edited Mar 19 '14 at 19:04

29

M-x comment-region, in Emacs' Python mode.

edited Mar 19 '14 at 19:04

Peter Mortensen

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answered Mar 23 '09 at 22:33

Joe W.

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M-; (comment-dwim) too – Yoo Sep 23 '09 at 08:23

score 18 · Answer 7 · answered Oct 01 '09 at 21:27

At least in VIM you can select the first column of text you want to insert using Block Visual mode (CTRL+V in non-windows VIMs) and then prepend a # before each line using this sequence:

I#<esc>

In Block Visual mode I moves to insert mode with the cursor before the block on its first line. The inserted text is copied before each line in the block.

score 13 · Answer 8 · edited Mar 19 '14 at 18:59

13

In vi:

Go to top of block and mark it with letter a.
Go to bottom of block and mark it with letter b

Then do

:'a,'b s!^!#!

edited Mar 19 '14 at 18:59

Peter Mortensen

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answered Sep 16 '10 at 17:48

Jerry

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Or: CTRL+V (and select lines) => :s/^/#/g If text highlighting is bothering you => :noh – Luciano Fantuzzi Aug 19 '18 at 01:52

score 11 · Answer 9 · answered Mar 07 '11 at 06:12

11

comm='''
Junk, or working code 
that I need to comment.
'''

You can replace comm by a variable of your choice that is perhaps shorter, easy to touch-type, and you know does not (and will not) occur in your programs. Examples: xxx, oo, null, nil.

answered Mar 07 '11 at 06:12

Harry

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This would be loaded to memory at run time, and if the intention is to create a comment you want the program to ignore it. Leading every line with a `#` would be better. Also, don't assign things to a variable called `null`, that's just asking for disaster. – James Geddes Jan 02 '21 at 23:52

score 6 · Answer 10 · edited May 12 '18 at 12:28

6

Yes, there is (depending on your editor). In PyDev (and in Aptana Studio with PyDev):

Ctrl + 4 - comment selected block
Ctrl + 5 - uncomment selected block

edited May 12 '18 at 12:28

Simeon Leyzerzon

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answered May 25 '12 at 15:41

jacanterbury

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but it is not pep8 format. – Romulus Dec 23 '16 at 10:55

score 6 · Answer 11 · edited Mar 19 '14 at 19:01

6

In Eclipse + PyDev, Python block commenting is similar to Eclipse Java block commenting; select the lines you want to comment and use Ctrl + / to comment. To uncomment a commented block, do the same thing.

edited Mar 19 '14 at 19:01

Peter Mortensen

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answered Jun 09 '12 at 19:00

arun

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Thorkil Holm-Jacobsen · Answer 12 · 2013-06-26T20:20:54.607

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In Visual Studio using the Python Tools for Visual Studio, blocks can be commented out by Ctrl+K, Ctrl+C and uncommented by Ctrl+K, Ctrl+U.

edited Jun 26 '13 at 20:20

answered Jan 10 '13 at 20:18

Thorkil Holm-Jacobsen

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This works for Visual Studio Code as well. – Eric Rohlfs Jan 10 '18 at 23:54
On Windows for VS Code ctrl + / – Deep Chatterjee Nov 22 '19 at 11:50

score 6 · Answer 13 · edited Mar 19 '14 at 18:59

6

I use Notepad++ on a Windows machine, select your code, type CTRL-K. To uncomment you select code and press Ctrl + Shift + K.

Incidentally, Notepad++ works nicely as a Python editor. With auto-completion, code folding, syntax highlighting, and much more. And it's free as in speech and as in beer!

edited Mar 19 '14 at 18:59

Peter Mortensen

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answered May 01 '10 at 03:30

dan

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score 4 · Answer 14 · edited Mar 19 '14 at 19:04

4

The only mechanism to comment out Python code (understood as code ignored by the interpreter) is the #.

As you say, you can also use string literals, that are not ignored by the interpreter, but can be completely irrelevant for the program execution.

edited Mar 19 '14 at 19:04

Peter Mortensen

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answered Mar 23 '09 at 22:31

Jaime Soriano

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score 2 · Answer 15 · edited Mar 19 '14 at 19:02

2

In Eclipse using PyDev, you can select a code block and press Ctrl + #.

edited Mar 19 '14 at 19:02

Peter Mortensen

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answered Feb 13 '13 at 03:20

Hamid

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to uncomment a block, use ctrl+shift+# – xingzhi.sg Dec 17 '13 at 01:03
This also works in komodo-edit for python – zhihong Feb 19 '15 at 15:52

score 1 · Answer 16 · answered Mar 24 '09 at 07:35

1

Triple quotes are OK to me. You can use ''' foo ''' for docstrings and """ bar """ for comments or vice-versa to make the code more readable.

answered Mar 24 '09 at 07:35

Anonymous

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My problem with triple quotes is that they actually are being checked for syntax. that has to be overhead that is unneeded for a comment. Case in point: if you had ''' /NPF ''' and run that in Python 3, it will throw a syntax error. So Python 3 is checking each triple quote for syntax validity. If you switch to # and comment the line, it is skipped. – continuousqa Sep 23 '14 at 18:38

score 1 · Answer 17 · edited Oct 26 '12 at 13:16

1

On Eric4 there is an easy way: select a block, type Ctrl+M to comment the whole block or Ctrl+alt+M to uncomment.

edited Oct 26 '12 at 13:16

deadly

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answered Jan 18 '12 at 12:20

Evaldo

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score 1 · Answer 18 · answered Jan 19 '12 at 22:56

Another editor-based solution: text "rectangles" in Emacs.

Highlight the code you want to comment out, then C-x-r-t #

To un-comment the code: highlight, then C-x-r-k

I use this all-day, every day. (Assigned to hot-keys, of course.)

This and powerful regex search/replace is the reason I tolerate Emacs's other "eccentricities".

score 0 · Answer 19 · edited Mar 19 '14 at 19:05

0

Use a nice editor like SciTe, select your code, press Ctrl + Q and done.

If you don't have an editor that supports block comments you can use a triple quoted string at the start and the end of your code block to 'effectively' comment it out. It is not the best practice though.

edited Mar 19 '14 at 19:05

Peter Mortensen

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answered Mar 24 '09 at 07:22

Christian Witts

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How to comment out a block of code in Python

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