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comp / comp.lang.python / Re: psycopg2: proper positioning of .commit() within try: except: blocks

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o Re: psycopg2: proper positioning of .commit() within try: except: blocksRob Cliffe

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Subject: Re: psycopg2: proper positioning of .commit() within try: except: blocks
From: Rob Cliffe
Newsgroups: comp.lang.python
Date: Sun, 8 Sep 2024 13:58 UTC
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Subject: Re: psycopg2: proper positioning of .commit() within try: except:
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On 07/09/2024 22:20, Karsten Hilbert via Python-list wrote:
> Am Sat, Sep 07, 2024 at 02:09:28PM -0700 schrieb Adrian Klaver:
>
>>> Right, and this was suggested elsewhere ;)
>>>
>>> And, yeah, the actual code is much more involved :-D
>>>
>> I see that.
>>
>> The question is does the full code you show fail?
>>
>> The code sample you show in your original post is doing something very different then
>> what you show in your latest post. At this point I do not understand the exact problem
>> we are dealing with.
> We are not dealing with an unsolved problem. I had been
> asking for advice where to best place that .commit() call in
> case I am overlooking benefits and drawbacks of choices.
>
> The
>
> try:
> do something
> except:
> log something
> finally:
> .commit()
>
> cadence is fairly Pythonic and elegant in that it ensures the
> the .commit() will always be reached regardless of exceptions
> being thrown or not and them being handled or not.
>
> It is also insufficient because the .commit() itself may
> elicit exceptions (from the database).
>
> So there's choices:
>
> Ugly:
>
> try:
> do something
> except:
> log something
> finally:
> try:
> .commit()
> except:
> log some more
>
> Fair but not feeling quite safe:
>
> try:
> do something
> .commit()
> except:
> log something
>
> Boring and repetitive and safe(r):
>
> try:
> do something
> except:
> log something
> try:
> .commit()
> except:
> log something
>
> I eventually opted for the last version, except for factoring
> out the second try: except: block.
>
> Best,
> Karsten
> --
> GPG 40BE 5B0E C98E 1713 AFA6 5BC0 3BEA AC80 7D4F C89B
Unless I'm missing something, the 1st & 3rd versions always do the
commit() even after the first bit fails, which seems wrong.
I suggest the 1st version but replacing "finally" by "else".  Then the
try-commit-except will not be executed if the "something" fails.
Perhaps the extra indentation of the second try block is a bit ugly, but
it is more important that it does the right thing.
If it is convenient (it may not be) to put the whole thing in a
function, you may feel that the follwing is less ugly:

try:
do something
except:
log something
return
try:
.commit()
except:
log some more
return

Best wishes
Rob Cliffe

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