Django: Make a query inside a class - django

Question

I want to make a query inside a class of my model. I have the following model where a contract is made when a person has a project.
class Person(models.Model):
name = models.CharField(max_length=32)
surname = models.CharField(max_length=32)
address = models.CharField(max_length=32)
is_doctor = models.NullBooleanField(blank=True, verbose_name=_(u"Phd?")
class Project(models.Model):
name = models.CharField(max_length=32, verbose_name=_(u"Name"))
principal_researcher = models.ForeignKey(Person, blank = True, verbose_name=_(u"Researcher associated with the project"))
class Contract(models.Model):
person = models.ForeignKey(Person) #person hired
project = models.ForeignKey(Project, blank = True, null = True) #related project
type_contract = models.CharField(max_length = 9, blank = True, verbose_name = _(u"Type of contract(Full time/grant/Partial time...)"))
starting_date = models.DateField(blank = True, null = True)
ending_date = models.DateField(blank = True, null = True)
term = models.CharField(max_length = 120, blank = True)
I want to create a class where the user will be able to make this query:
Tell me all the people, without Phd, with full time contract with a contract among two dates.
So the user only has to enter two dates to get the query.
(All of this from the Admin interface)

Answer 1

I don't know what you mean by "inside a class".
You can make your query like this:
Person.objects.filter(
is_doctor=False,
contract__type_contract='full',
contract__starting_date__gte=start_date,
contract__ending_date__lte=end_date
)
If you want to define a method to execute this query, that is normally done inside a model manager:
class PersonManager(models.Manager):
def full_time_no_doctors_contract_between(self, start_date, end_date):
return self.filter(...)
class Person(models.Model):
...
objects = PersonManager()
and now you can do:
Person.objects.full_time_no_doctors_contract_between(start_date, end_date)