[Tutor] diferent between " "(empty string) and None as condition

[Cameron Simpson]

On 25Apr2020 12:01, boB Stepp <robertvstepp at gmail.com> wrote:
>On Sat, Apr 25, 2020 at 2:38 AM Cameron Simpson <cs at cskk.id.au> wrote:
>> On 24Apr2020 23:07, boB Stepp <robertvstepp at gmail.com> wrote:
>> >Would you please show a realistic example where one might do this --
>> >where None can't be used as a sentinel because it is otherwise
>> >occupied?
>>
>> Anything where a valid function result might be None.
>
>Ah.  Just this one sentence made the light bulb glow brightly!

Aye. A sentinel is by definition a not-in-the-domain value; that is its 
whole purpose.

>OT:  Cameron, just for your posts to Tutor where I am being responded
>to, I find Gmail sending all of your posts to spam.

This is my suspicion as well. Just on the basis of lots of threads where 
it is like I haven't posted at all (the discussion is like I haven't 
been seen, versus simply not being helpful).

>I don't know much
>about the inner workings of email, but I notice in the details Gmail
>provides:
>
>from:Cameron Simpson <cs at cskk.id.au> reply-to:tutor at python.org,
>boB Stepp <robertvstepp at gmail.com>,
>tutor <tutor at python.org>
>to:boB Stepp <robertvstepp at gmail.com>
>
>The Tutor list is duplicated.  Would this be the cause of straight to
>spam?  If yes, is this something correctable on your end?  Not that I
>want to impose on your valuable time!

I often reply to the author as well as the list, but set reply-to to the 
list to avoid off-list accidents. I don't think this affects GMail's 
decisions (can't test that).

Are there other header on the message at your end indicating what GMail 
thinks? You may need to view-source on the message to see them. We 
should take the email/spam side of this discussion off list to personal 
email.

Other things that might affect this is lack of SPF on my domain. I could 
make one, but since we routinely send via our ISP mail relays rather 
than through our mail server this there's nothing very useful we can put 
in the SPF :-( (Think: mobile phone, sending via the phone company's 
mail relay.)

Cheers,
Cameron Simpson <cs at cskk.id.au>