On 5/8/2009 5:58 PM, Lee Hinde wrote:
> On Fri, May 8, 2009 at 5:12 PM, Lee Hinde <leehi...@gmail.com> wrote:
>> On Fri, May 8, 2009 at 4:48 PM, George Song <geo...@damacy.net> wrote:
>>> On 5/8/2009 4:32 PM, Lee Hinde wrote:
>>>> Hi;
>>>>
>>>> I get the error below at a point I'm trying to add 1 to an int field.
>>>> I'm understanding the error that django doesn't know what the type is
>>>> for sn.
>>>>
>>>>
>>>> Model:
>>>>
>>>> class Sequence_Number(models.Model):
>>>> Sequence_Name = models.CharField(max_length=100)
>>>> Next_Sequence_Number = models.IntegerField()
>>>> LastUpdate = models.DateField(auto_now = True)
>>>> dupefixed = models.DateField(blank=True,null=True)
>>>>
>>>> def __unicode__(self):
>>>> return self.Sequence_Name
>>>>
>>>> Sequence Number function:
>>>>
>>>> @transaction.autocommit
>>>> def get_SequenceNumber(itemToSequnce):
>>>> try:
>>>> sn = Sequence_Number.objects.get(Sequence_Name=itemToSequnce)
>>>> except Sequence_Number.DoesNotExist:
>>>> sn = Sequence_Number(Sequence_Name=itemToSequnce)
>>>> next_number = sn.Next_Sequence_Number
>>>> sn.Next_Sequence_Number += 1
>>>> sn.save()
>>>> return next_number
>>>>
>>>> def buildSlug(slug):
>>>> slug = "slug__%s" % (slug)
>>>> next_Num = get_SequenceNumber(slug)
>>>> slug_with_number = "%s%d" % (slug,next_Num)
>>>> return slug_with_number
>>>>
>>>>
>>>>
>>>> Traceback:
>>>>
>>>> File "<console>", line 2, in <module>
>>>> File
>>>> "/Users/leehinde/Documents/Clients/RecEnrollTNV/RecEnroll/recenrolltnv/../recenrolltnv/recenroll/models.py",
>>>> line 314, in save
>>>> self.Slug = buildSlug(start)
>>>> File
>>>> "/Users/leehinde/Documents/Clients/RecEnrollTNV/RecEnroll/recenrolltnv/../recenrolltnv/recenroll/models.py",
>>>> line 20, in buildSlug
>>>> next_Num = get_SequenceNumber(slug)
>>>> File "/Library/Python/2.5/site-packages/django/db/transaction.py",
>>>> line 223, in _autocommit
>>>> return func(*args, **kw)
>>>> File
>>>> "/Users/leehinde/Documents/Clients/RecEnrollTNV/RecEnroll/recenrolltnv/../recenrolltnv/recenroll/models.py",
>>>> line 14, in get_SequenceNumber
>>>> sn.Next_Sequence_Number += 1
>>>> TypeError: unsupported operand type(s) for +: 'NoneType' and 'int'
>>> {{{
>>> try:
>>> sn = Sequence_Number.objects.get(Sequence_Name=itemToSequnce)
>>> except Sequence_Number.DoesNotExist:
>>> sn = Sequence_Number(Sequence_Name=itemToSequnce)
>>> next_number = sn.Next_Sequence_Number
>>> }}}
>>>
>>> Well, in your except block, you're just instantiating a Sequence_Number
>>> object, so of course it doesn't have the Next_Sequence_Number attribute yet.
>>>
>>> Did you mean to do:
>>> {{{
>>> Sequence_Number.objects.create(Sequence_Name=itemToSequnce)
>>> }}}
>>> ?
>>>
>> I may mean that. :-) I was trying to emulate the documentation around
>> the get_or_create method.
>>
>> The documentation around transaction implied that the transaction
>> would be closed when the object was saved,, I wasn't sure if
>> get_or_create would end the transaction.
>>
>> In any case I get the same error if I seed the Next_Sequence_Number.
>> sn =
>> Sequence_Number(Sequence_Name=itemToSequnce,Next_Sequence_Number=0)
>> or
>>
>> Sequence_Number.objects.create(Sequence_Name=itemToSequnce,Next_Sequence_Number=0)
>>
>
>
>
> I moved everything out to the shell and it worked. That made me think
> that there must be a typo or somesuch in what I'd originally done. I
> also may not understand mutability in Python just yet. After futzing
> around some I ended up with this and it works now:
>
> @transaction.autocommit
> def get_SequenceNumber(itemToSequnce):
> try:
> sn = Sequence_Number.objects.get(Sequence_Name=itemToSequnce)
> except Sequence_Number.DoesNotExist:
> sn =
> Sequence_Number.objects.create(Sequence_Name=itemToSequnce,Next_Sequence_Number=0)
> next_number = sn.Next_Sequence_Number
> sn.Next_Sequence_Number += 1
> sn.save()
> return next_number
>
> def buildSlug(input_data):
> slug = "%s__" % (input_data)
> print "slug: %s"%(slug)
> next_Num = get_SequenceNumber(slug)
> print "nn: %d"%(next_Num)
> slug_with_number = "%s%d" % (slug,next_Num)
> print "slugwnum: %s"%(slug_with_number)
> return slug_with_number
>
>
> George, thanks for the help. It's greatly appreciated.
I'm glad it worked out for you. While I don't know your specific use
case, it feels more natural to me to do something like this:
{{{
Sequence_Number.next_for(itemToSequence)
}}}
So I would encourage you to promote the get_SequenceNumber utility
function to a Sequence_Number class method.
--
George
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