PEP 308: A PEP Writer's Experience - PRO

[Tim Peters]

[Michael Chermside]
> If a ternary expression is available, then things can be done in
> expressions which would be impossible without it. lambda is the
> example most often given, but I think a different example is
> more compelling. Suppose you want to write a line of logging
> into your program:
>
>        print "x = " + x.getDisplayString()
>
> but you have to allow for the fact that x might be None. With
> a ternary expression, you can write this:
>
>        print "x = " + x.getDisplayString() if x else "None"


[Aahz]
> Why not
>
>     print 'x =', x.getDisplayString()
>
> or
>
>     print 'x = ' + str(x.getDisplayString())


Presumably because, if x is None, None.getDisplayString() will blow up.

> The point is that many of the supposed uses for ternary do have simple,
> effective workarounds.

This isn't one of 'em <wink>.

OTOH, when I read Micahel's post, I had no idea whether

    print "x = " + x.getDisplayString() if x else "None"

would group as:

    print ("x = " +   (x.getDisplayString() if x else "None"))

or as:

    print (("x = " + x.getDisplayString())   if x else "None")

and I didn't even know which way he *intended*.  Spelled with an if-
statement instead, the intent is obvious instead of a puzzle.