Question

I think most people agree that trailing whitespace is not good practice. A lot of editors will display it for you or automatically strip it out.

Consider this Python function as a simple example:

The extra whitespace on lines 11 and 13 are wrong. What I’m wondering about is line 10. Should a blank line inside a control block that doesn’t change indentation have leading whitespace?

Most editors I’ve used will keep the cursor at the indentation level from the preceding line, so making a blank line without leading whitespace takes some extra formatting. What’s the best practice? Should line 10 have leading whitespace or not?

Answer 1

I’ll try to answer your question sticking to your Python example, quoting their style guide.

From PEP-8:

Method definitions inside a class are separated by a single blank line.

From Wikipedia (blank line):

A blank line usually refers to a line containing zero characters (not counting any end-of-line characters); though it may also refer to any line that does not contain any visible characters (consisting only of whitespace).

If you believe the Wikipedia definition, you might ask why zero characters is preferred.

For one it’s simpler, even if autoindent is turned on in your editor, you’re just filling your file with extra bytes for no good reason.

Second, a regex for a zero character blank line is simpler as well, ‘^$’ usually vs something like ‘^\s*$’.

As other answers have pointed out, it makes no difference execution wise to put in whitespace. With no good reason to do so, I would say the best practice is to leave it out and keep it simple. Can you imagine a situation where a zero character line would be treated differently than a line with some whitespace? I would hate to program in that language. Putting in whitespace seems baroque to me.