On Tue, Sep 29, 2015 at 7:57 PM, Andrew Barnert via Python-ideas <python-ideas@python.org> wrote:

If this is going to be a keyword rather than a symbol, it really has to read like English, or at least like abbreviated English,

I am -1 on this whole idea, but the keyword that comes to mind is "def":

x def []

may be read as x DEFaulting to [].

If this was a Python 4 idea, I would suggest repurposing the rarely used xor operator: ^ and make x ^ y return the non-None of x and y or None if both are None.