What is prefered: 'string' or "string"? (Should be in PEP8 ?)

[Philipp Lenssen]

"John Baxter" <jwbaxter at spamcop.net> wrote in message
news:jwbaxter-B5D4A7.19244624042002 at corp.supernews.com...
>..
> I use single quote (that is, apostrophe) to avoid a shift key
> manipulation.  Unless I forget.  And of course if the string begins with
> a shifted character, the manipulation is deferred, not avoided.
>..

I need to press Shift to get a single quote. Or double-quote, greater-than,
and $.
I'm not sure what is exclusive german keyboard layout here.