how to let argument be optional falling back to certain integer
Chris Angelico <rosuav at gmail.com> writes:
> On Sun, Jun 21, 2020 at 2:02 AM Boris Dorestand <bdorestand at example.com> wrote:
>> I just wrote
>> def f(y, N, k = None):
>> k = k or (N - 1)
>> return k
>> I was surprised to find out that 0 == False, so f(7, 31, 0) produces 31.
>> I'd like 0 to be a valid choice for k.
>> How do you guys let k be an optional argument such that it defaults to
>> N - 1?
> The easiest way is to explicitly check for None.
> if k is None: k = N - 1
Got it. That's clear code.
> Zero being false shouldn't be a surprise. If None can count as false,
> then so should other "emptiness" values. (Remember, the canonical
> falseness value is False, not None.)
This is true. I have written 0 as false in C so many times. But
clearly for me times have changed... I now look at numbers as a thing
in their own special class not to be confused as truth-values. (So much
so that I fell for this.) But I confess I still think of numbers as all
TRUE. (Even zero!)
Anyway, I kind of replied just to thank you all for the great group this
is. ChrisA, I don't know how can keep up with this newsgroup, but you
do. This is crazy. Years go by and when I come back, there you are
still. You're priceless.