PyEnty¶

A simple object-document mapper written in python for motor( a driver for MongoDB) and to be used in tornado applications. Although, motor accomplish the hard task of provide async methods to access mongodb, we still have to get along with classic python dictionary which force us to create and maintain mapping of dicts-to-instance or instance-to-dicts.

Simple example using motor:

#saves a dict with some values
@gen.coroutine
def save_product():
    product = {'name':'cell phone', 'description':'black phone', 'price':10.5}
    # motor collection
    objectid = yield collection.insert(product)

#read from motor's find_one method
@gen.coroutine
def find_product():
    product = yield collection.find_one({'_id': objectid})
    name = product['name']
    description = product['description']
    price = product['price']

There’s no problem if you prefer to work like this, but you always have to use some kind of mapping for any new added class and maintain your existing mapping when something changes. If you really want to release yourself from boring task of accessing key/value whenever you write code to read/write from/to database, we suggest you to work such as in the example below:

defining entities:

class ShippingOptions(Entity):
    name = Str()
    def __init__(self, name=""):
        self.name = name

class Product(Entity):
    name = Str()
    description = Str()
    price = Float()
    shipping_options = List(ShippingOptions)

    def __init__(self, name="", description="", price=0.0):
        self.name = name
        self.description = description
        self.price = price

    def add_shipping_option(self, shipping_option):
        assert isinstance(shipping_option, Entity)
        self.shipping_options.append(shipping_option)

Save and find from mongodb:

@gen.coroutine
def save_product():
    emanager = EntityManager(Product)
    product = Product('book', 'book of the year', 35.00)

    # adding shipping options
    product.add_shipping_option(ShippingOptions('option1'))
    product.add_shipping_option(ShippingOptions('option2'))
    product.add_shipping_option(ShippingOptions('option3'))

    object_id = yield self.emanager.save(product)

@gen.coroutine
def find_product():
    emanager = EntityManager(Product)
    saved_product = yield self.emanager.find_one(_id=object_id)

    #read product attributes
    name = saved_product.name
    description = saved_product.description
    price = saved_product.price

    #read shipping options
    #it's just an example to show that pyenty maps results to object
    for option in saved.product.shipping_options:
        self.name = option.name