[pybsddb] Please add this simple function

[Yong Li]

Well, has_key is also not protected by transactions, right? So I don't
think it's worse off than using has_key. Maybe you can just make it
clear that __contains__ just acts as an alias for has_key so that it
acts more like a Python dict. Of course I defer judgments to you since
you know more about this than I do.

On Mon, Apr 27, 2009 at 1:21 PM, Jesus Cea <jcea at argo.es> wrote:
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> Yong Li wrote:
>> Hi,
>>
>> Please add a __contains__ to the DB object in pybsddb. Right now if you do
>>
>> key in db
>>
>> Python treats db as a iterable and iterates across the entire db
>> because there is no __contains__ but there is an __iter__. Please add
>> this to DB:
>>
>> def __contains__(self, key):
>>     return self.has_key(key)
>
> The code is far more complicated, because we need to implement this in C.
>
> This change will be available in pybsddb 4.7.6. But, beware, the
> "__contains__()" call will be NOT protected by transactions.
>
> I don't actually like this. Would you rather prefer to raise an
> exception when doing "if key in DB:" to warning about the lack of
> transaction isolation?. Recent versions of Berkeley DB has a
> "DB.exists()" *transactional* function. I can implement something
> similar for all supported BDB versions.
>
> In my "to to" I just wrote:
>
> """
> * 20090427: "__contains__()" is not transactionally protected. This is
>  a problem. Maybe we should raise an exception to avoid the usage
>  of patterns like "if key in DB", not transactionally protected.
>  Think about this.
>
> """
>
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