[Python-3000] About "daemon" in threading module

[Guido van Rossum]

On Thu, Sep 4, 2008 at 8:47 AM, Antoine Pitrou <solipsis at pitrou.net> wrote:
> Jesus Cea <jcea <at> jcea.es> writes:
>>
>> First we had "thread.setDaemon()". This was not PEP8, so Python 3.0
>> renamed it to "thread.set_daemon()". Lately Python 3.0 changes the
>> method to an attribute "thread.daemon".
>>
>> I think the last change is risky, because you can mistype and create a
>> new attribute, instead of set daemon mode. Since daemon mode is only
>> usually visible when things goes wrong (the main thread dies), you can
>> miss the bug for a long time.
>
> I've never understood why the "daemon" flag couldn't be passed as one of the
> constructor arguments. It would make code shorter, and avoid the mistyping risk
> mentioned by Jesus. It also sounds saner, since you shouldn't change the flag
> after the thread is started anyway.

As to the why question, this was done to match the Java Thread class.
I don't want to speculate why the Java API was designed this way --
possibly it was a relic of an earlier API version in Java, but
possibly there's a reason I can't fathom right now. After all, there
are excellent reasons why start() is a separate call...

-- 
--Guido van Rossum (home page: http://www.python.org/~guido/)