Question about transaction usage

[Douglas Philips]

On or about 2009 Oct 4, at 10:20 AM, Greg Ward indited:
> On Sat, Oct 3, 2009 at 5:36 PM, Matt Mackall <mpm at selenic.com> wrote:
>> Unfortunately, destructors in Python are basically useless. If an
>> exception is thrown, the traceback object will hold references to  
>> every
>> stack frame in the call chain, preventing the destructors from  
>> getting
>> invoked in a timely fashion (and sometimes at all!).
>>
>> So we make a point of manually destroying locks and transactions.
>
> Got it.  Thanks.
> ...
> I think the most useful thing I learned from Java is that you must
> never rely on destructors being called: if your object holds
> resources, give it an explicit close() method.  (C)Python destructors
> are more deterministic than Java destructors, but the rule holds.

That's a bit confusing. I haven't looked at the hg source in a while,  
but last I did, file objects were not being explicitly closed, and the  
attitude seemed to be that destructors/gc would just handle that.  
There is some deep asymmetry here or ???

-Doug