Models

class Model

First, you must define your Model. Banjo provides four field types:

• BooleanField (True, False)

• IntegerField (1, -102)

• FloatField (0.045, 11.5)

• StringField (“alligator”, “hazelnut”)

All models have id as a default field. You do not need to include this.

To create a model:

# app/models.py
from banjo.models import Model, StringField, IntegerField, BooleanField

class Person(Model):
   name = StringField()
   age = IntegerField()
   student = BooleanField()

   def update_age(self):
      self.age +=1
      self.save()

   def json_response(self):
      return {
         "id": self.id,
         "name", self.name,
         "age", self.age,
         "student", self.student

To create an instance of the model in the Banjo shell: banjo --shell

>>> one_person = Person(name='Dragon', age=15, student=True)
>>> one_person.save()

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All Banjo models have two funcitons built it. You can override in them in the class definition.

objects.from_dict()

Takes a dictionary a nicely formats it to easily create a new object

Returns:

an instance of the object

example:

>>> another_person_dict = {
   'name':'Snail',
   'age': 88,
   'student': False}
>>> another_person = Person.from_dict(another_person_dict)
>>> another_person.save()

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Model Querying

When querying the Banjo database, it return a QuerySet. A QuerySet is a list of objects.

objects.all()

Returns:

a QuerySet of all the instances of the object

example:

Person.objects.all()

To iterate, or loop, through a QuerySet:

# Prints each name of all Persons one at a time
for person in Person.objects.all():
   print(person)

objects.get()

Returns:

a single of object

example:

Person.objects.get(id=1)

objects.count()

Returns:

an interger representing the number in the QuerySet

example:

Person.objects.count()

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objects.filter()

Returns:

a QuerySet matching the filter parameters

example:

# Deletes the instance of Person with an id of 1
Person.objects.filter(age=16)

objects.order_by()

Returns:

a QuerySet ordered in ascending order. For strings ascending order is alphabetical, for integers ascending order is numerical.

example:

# Returns a QuerySet of Persons in alphabetical order by name
Person.objects.order_by('name')

# Returns a QuerySet of Persons in reverse alphabetical order by name
Person.objects.order_by('-name')

# Returns a QuerySet of Persons in random order by name
Person.objects.order_by('?')

objects.first()

Returns:

the first object in the QuerySet

example:

# Returns the first Person by age
Person.objects.first()

# Returns the first Person with the lowest age
Person.objects.orderby('age').first()

objects.exists()

Returns:

a Boolean value if the QuerySet returns any results

example:

# Returns a Boolean value representing if any Persons exist
Person.objects.exists()

# Returns a Boolean value representing if any Persons with the age of 10 exist
Person.objects.filter(age=10).exists()

objects.delete()

Deletes all the objects in a QuerySet

example:

# Deletes the instance of Person with an id of 1
Person.objects.get(id=1).delete()

objects.exclude()

Returns:

a QuerySet containing all objects except those that match the parameters

example:

# Returns a QuerySet of Persons without an age of 12
Person.objects.exclude(age=12)

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Advanced Filtering

objects.filter(__startswith=)

Returns:

a QuerySet containing all objects that start with a specific parameter

example:

# Returns a QuerySet of Persons with names that include the letter 'a'
Person.objects.filter(name__startswith='a')

objects.filter(__endswith=)

Returns:

a QuerySet containing all objects that end with a specific parameter

example:

# Returns a QuerySet of Persons with names that include the letter 'a'
Person.objects.filter(name__endswith='n')

objects.filter(__contains=)

Returns:

a QuerySet containing all objects that contain a specific parameter

example:

# Returns a QuerySet of Persons with names that start the letter 'b'
Person.objects.filter(name__contains='brown')

Conditional Symbols

objects.filter(__gt=)

• gt: greater than

• gte: greater than or equal to

• lt: less than

• lte: less than or equal to

  example:

  # Returns a QuerySet of Persons with an age greater than 15
  Person.objects.filter(age__gt=15)
  
  # Returns a QuerySet of Persons with an age less than or equal 55
  Person.objects.filter(age__lt=55)
  

Chaining Filtering

Query functions are easily chained together to create a more specific QuerySet.

example:

# Returns a QuerySet of Persons with an age greater than 15 and names that start with 'a'
Person.objects.filter(age__gt=15).filter(name__starswith="a")

# Returns a count of Persons with an age greater than 15 and names that start with 'a'
Person.objects.filter(age__gt=15).filter(name__starswith="a").count()

To iterate, or loop, through a chained QuerySet:

# Prints each name of Persons where student is True
for person in Person.objects.filter(student=True):
   print(person.name)

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