This is an indirect answer--not answering the style question directly, but it's the practical answer in general, so it's worth mentioning.
I find it extremely rare to need to write multi-line conditionals. There are two factors to this:
- Don't wrap code at 80 columns. PEP-8's advice on this subject is ancient and harmful; we're well past the days of 80x25 terminals and editors that can't sensibly handle wrapping. 100 columns is fine, and 120 is usually acceptable, too.
- If conditions become so long that they still need to wrap, it's usually reasonable to move some of the logic out of the conditional and into a separate expression. This also tends to help readability.
Grepping through my recent projects, around 12kloc, there's only one conditional long enough that it needed to be wrapped; the issue simply very rarely arises. If you do need to do this, then as nosklo says, indent it separately--as you noticed, indenting it to the same level as the block beneath it is confusing and hard to read.
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