question of style

[Scott David Daniels]

Duncan Booth wrote:
> Simon Forman <sajmikins at gmail.com> wrote:
>> ...
>> if self.higher is self.lower is None: return
>> ...

> As a matter of style however I wouldn't use the shorthand to run two 'is' 
> comparisons together, I'd write that out in full if it was actually needed 
> here.

Speaking only to the style issue, when I've wanted to do something like
that, I find:

       if self.higher is None is self.lower:
           ...

more readable, by making clear they are both being compared to a
constant, rather than compared to each other.

More often, I've used code like:

       if <expr1> is not None is not <expr2>:
           ...

since I am usually working on non-defaulting cases in the body.
I find the form above simpler to read than:

       if <expr1> is not None and <expr2> is not None:
           ...

I do draw the line at two, though, and with three or more I'll
paren-up a list of parallel comparisons:

       if (<expr1> is not None
         and <expr2> is not None
         and <expr3> is not None):
           ...

--Scott David Daniels
Scott.Daniels at Acm.Org