python - Help with creating a custom create and a custom get method -

i have 2 models so:

class visit(models.model):     id = models.autofield(primary_key=true)     name = models.charfield(max_length=65535, null=false)  class session:     id = models.autofield(primary_key=true)     visit = models.foreignkey(visit)     sequence_no = models.integerfield(null = false) 

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i'd 2 write custom create method in session model when write this:

visitor = vistor.objects.get(id=1) new_session = session.objects.create_new_session(visit=visitor) 

...i new record in session table next consecutive sequence number visitor i.e. 3. here's sample data

visitor sequence_no ------- ----------- 1         1 1         2 2         1 2         2 1         3 (this row created) 

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the other writing custom method in session model write:

visitor = vistor.objects.get(id=1) new_session = session.objects.get_session(visit=visitor, sequence_no=3) 

...i previous record of visitor highest sequence number. here's sample data

visitor sequence_no ------- ----------- 1         1 1         2 (this row fetched) 2         1 2         2 1         3  

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could tell me how accomplish please? should code in model or manager?

thanks everyone.

this in manager sessions. (untested):

class sessionmanager(models.manager):     def new_session(self, visit, **kwargs):         vs = self.model.objects.filter(visit=visit).order_by("-sequence_no")[:1]         if len(vs):             kwargs.update({"sequence_no": vs.sequence_no + 1})         return super(sessionmanager, self).create(visit=visit, **kwargs) 

as getting session when have visit, , sequence_no there shouldn't custom code needed that.