Python 的資料建模

from google.appengine.ext import db

class Pet(db.Model):
    name = db.StringProperty(required=True)
    type = db.StringProperty(required=True, choices=set(["cat", "dog", "bird"]))
    birthdate = db.DateProperty()
    weight_in_pounds = db.IntegerProperty()
    spayed_or_neutered = db.BooleanProperty()

from google.appengine.api import users

pet = Pet(name="Fluffy",
          type="cat")
pet.weight_in_pounds = 24

class Person(db.Expando):
    first_name = db.StringProperty()
    last_name = db.StringProperty()
    hobbies = db.StringListProperty()

p = Person(first_name="Albert", last_name="Johnson")
p.hobbies = ["chess", "travel"]

p.chess_elo_rating = 1350

p.travel_countries_visited = ["Spain", "Italy", "USA", "Brazil"]
p.travel_trip_count = 13

del p.chess_elo_rating

p1 = Person()
p1.favorite = 42
p1.put()

p2 = Person()
p2.favorite = "blue"
p2.put()

p3 = Person()
p3.put()

people = db.GqlQuery("SELECT * FROM Person WHERE favorite < :1", 50)
# people has p1, but not p2 or p3

people = db.GqlQuery("SELECT * FROM Person WHERE favorite > :1", 50)
# people has no results

from google.appengine.ext import db
from google.appengine.ext.db import polymodel

class Contact(polymodel.PolyModel):
    phone_number = db.PhoneNumberProperty()
    address = db.PostalAddressProperty()

class Person(Contact):
    first_name = db.StringProperty()
    last_name = db.StringProperty()
    mobile_number = db.PhoneNumberProperty()

class Company(Contact):
    name = db.StringProperty()
    fax_number = db.PhoneNumberProperty()

p = Person(phone_number='1-206-555-9234',
           address='123 First Ave., Seattle, WA, 98101',
           first_name='Alfred',
           last_name='Smith',
           mobile_number='1-206-555-0117')
p.put()

c = Company(phone_number='1-503-555-9123',
            address='P.O. Box 98765, Salem, OR, 97301',
            name='Data Solutions, LLC',
            fax_number='1-503-555-6622')
c.put()

for contact in Contact.all():
    print 'Phone: %s\nAddress: %s\n\n' % (contact.phone_number,
                                          contact.address)

for company in Company.all()
    # ...

class MyModel(db.Model):
    string = db.StringProperty()

obj = MyModel()

# Python Unicode literal syntax fully describes characters in a text string.
obj.string = u"kittens"

# unicode() converts a byte string to a Unicode string using the named codec.
obj.string = unicode("kittens", "latin-1")

# A byte string is assumed to be text encoded as ASCII (the 'ascii' codec).
obj.string = "kittens"

# Short string properties can be used in query filters.
results = db.GqlQuery("SELECT * FROM MyModel WHERE string = :1", u"kittens")

class MyModel(db.Model):
    text = db.TextProperty()

obj = MyModel()

# Text() can take a Unicode string.
obj.text = u"lots of kittens"

# Text() can take a byte string and the name of an encoding.
obj.text = db.Text("lots of kittens", "latin-1")

# If no encoding is specified, a byte string is assumed to be ASCII text.
obj.text = "lots of kittens"

# Text properties can store large values.
obj.text = db.Text(open("a_tale_of_two_cities.txt").read(), "utf-8")

class MyModel(db.Model):
    blob = db.BlobProperty()

obj = MyModel()

obj.blob = open("image.png").read()

class MyModel(db.Model):
    numbers = db.ListProperty(long)

obj = MyModel()
obj.numbers = [2, 4, 6, 8, 10]

obj.numbers = ["hello"]  # ERROR: MyModel.numbers must be a list of longs.

# Get all entities where numbers contains a 6.
results = db.GqlQuery("SELECT * FROM MyModel WHERE numbers = 6")

# Get all entities where numbers contains at least one element less than 10.
results = db.GqlQuery("SELECT * FROM MyModel WHERE numbers < 10")

class FirstModel(db.Model):
    prop = db.IntegerProperty()

class SecondModel(db.Model):
    reference = db.ReferenceProperty(FirstModel)

obj1 = FirstModel()
obj1.prop = 42
obj1.put()

obj2 = SecondModel()

# A reference value is the key of another entity.
obj2.reference = obj1.key()

# Assigning a model instance to a property uses the entity's key as the value.
obj2.reference = obj1
obj2.put()

obj2.reference.prop = 999
obj2.reference.put()

results = db.GqlQuery("SELECT * FROM SecondModel")
another_obj = results.fetch(1)[0]
v = another_obj.reference.prop

try:
  obj1 = obj2.reference
except db.ReferencePropertyResolveError:
  # Referenced entity was deleted or never existed.

# To fetch and iterate over every SecondModel entity that refers to the
# FirstModel instance obj1:
for obj in obj1.secondmodel_set:
    # ...

class FirstModel(db.Model):
    prop = db.IntegerProperty()

# This class raises a DuplicatePropertyError with the message
# "Class Firstmodel already has property secondmodel_set"
class SecondModel(db.Model):
    reference_one = db.ReferenceProperty(FirstModel)
    reference_two = db.ReferenceProperty(FirstModel)

class FirstModel(db.Model):
    prop = db.IntegerProperty()

# This class runs fine
class SecondModel(db.Model):
    reference_one = db.ReferenceProperty(FirstModel,
        collection_name="secondmodel_reference_one_set")
    reference_two = db.ReferenceProperty(FirstModel,
        collection_name="secondmodel_reference_two_set")