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USAGE.md

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Usage examples

Get the service

import requests
import pyodata

SERVICE_URL = 'http://services.odata.org/V2/Northwind/Northwind.svc/'

# Create instance of OData client
client = pyodata.Client(SERVICE_URL, requests.Session())

Get the service proxy client for an OData service requiring authentication

Let's assume you need to work with a service at the URL https://odata.example.com/Secret.svc and User ID is 'MyUser' with the password 'MyPassword'.

PyOData expects that the used HTTP library will take care about this task.

In this example we configure Session of python-requests to handle user authentication.

import requests
import pyodata

SERVICE_URL = 'https://odata.example.com/Secret.svc'

session = requests.Session()
session.auth = ('MyUser', 'MyPassword')

# Create instance of OData client
client = pyodata.Client(SERVICE_URL, session)

Get one entity identified by its key value

# Get employee identified by 1 and print employee first name
employee1 = client.entity_sets.Employees.get_entity(1).execute()
print(employee1.FirstName)

Get one entity identified by its key value which is not scalar

# Get number of orderd units in the order identified by ProductID 42 and OrderID 10248.
order = client.entity_sets.Order_Details.get_entity(OrderID=10248, ProductID=42).execute()
print(order.Quantity)

Get all entities of an entity set

# Print unique identification (Id) and last name of all cemployees
employees = client.entity_sets.Employees.get_entities().select('EmployeeID,LastName').execute()
for employee in employees:
    print(employee.EmployeeID, employee.LastName)

Get entities matching a filter

# Print unique identification (Id) of all employees with name John Smith
smith_employees_request = client.entity_sets.Employees.get_entities()
smith_employees_request = smith_employees_request.filter("FirstName eq 'John' and LastName eq 'Smith'")
for smith in smith_employees.execute():
    print(smith.EmployeeID)

Get entities matching a filter in more Pythonic way

from pyodata.v2.service import GetEntitySetFilter

# Print unique identification (Id) of all employees with name John Smith
smith_employees_request = client.entity_sets.Employees.get_entities()
smith_employees_request = smith_employees_request.filter(GetEntitySetFilter.and_(
                                                         smith_employees_request.FirstName == 'Jonh',
                                                         smith_employees_request.LastName == 'Smith'))
for smith in smith_employees_request.execute():
    print(smith.EmployeeID)

Get a count of entities

# Print a count of all employees
count = client.entity_sets.Employees.get_entities().count().execute()
print(count)

Get a count of entities via navigation property

# Print a count of all orders associated with Employee 1
count = client.entity_sets.Employees.get_entity(1).nav('Orders').get_entities().count().execute()
print(count)

Creating entity

You need to use the method set which accepts key value parameters:

employee_data = {
    'FirstName': 'Mark',
    'LastName': 'Goody',
    'Address': {
        'HouseNumber': 42,
        'Street': 'Paradise',
        'City': 'Heaven'
    }
}

create_request = client.entity_sets.Employees.create_entity()
create_request.set(**employee_data)

new_employee_entity = create_request.execute()

or you can do it explicitly:

create_request = client.entity_sets.Employees.create_entity()
create_request.set(
    FirstName='Mark',
    LastName='Goody',
    Address={
        'HouseNumber': 42,
        'Street': 'Paradise',
        'City': 'Heaven'
    }
)

new_employee_entity = request.execute()

Batch requests

Example of batch request that contains 3 simple entity queries

client = pyodata.Client(SERVICE_URL, requests.Session())

batch = client.create_batch()

batch.add_request(client.entity_sets.Employees.get_entity(108))
batch.add_request(client.entity_sets.Employees.get_entity(234))
batch.add_request(client.entity_sets.Employees.get_entity(23))

response = batch.execute()

print(response[0].EmployeeID, response[0].LastName)
print(response[1].EmployeeID, response[1].LastName)
print(response[1].EmployeeID, response[1].LastName)

Example of batch request that contains simple entity query as well as changest consisting of two requests for entity modification

client = pyodata.Client(SERVICE_URL, requests.Session())

batch = client.create_batch()

batch.add_request(client.entity_sets.Employees.get_entity(108))

changeset = client.create_changeset()

changeset.add_request(client.entity_sets.Employees.update_entity(45).set(LastName='Douglas'))

batch.add_request(changeset)

response = batch.execute()

print(response[0].EmployeeID, response[0].LastName)

Calling a function import

products = client.functions.GetProductsByRating.parameter('rating', 16).execute()
for prod in products:
    print(prod)

Error handling

PyOData returns HttpError when the response code does not match the expected code.

In the case you know the implementation of back-end part and you want to show accurate errors reported by your service, you can replace HttpError by your sub-class HttpError by assigning your type into the class member VendorType of the class HttpError.

from pyodata.exceptions import HttpError


class MyHttpError(HttpError):

    def __init__(self, message, response):
        super(MyHttpError, self).__init__('Better message', response)


HttpError.VendorType = MyHttpError

The class pyodata.vendor.SAP.BusinessGatewayError is an example of such an HTTP error handling.

Metadata tests

By default, the client makes sure that references to properties, entities and entity sets are pointing to existing elements.

The most often problem that we had to deal with was an invalid ValueList annotion pointing to a non-existing property.

To enable verification of service definition, the client instance of the class Service publishes the property schema which returns an instance of the class Schema from the module pyodata.v2.model and it contains parsed $metadata.

List of the defined EntitySets

If you need to iterate over all EntitySets:

for es in service.schema.entity_sets:
     print(es.name)

or if you just need the list of EntitySet names:

entity_set_names = [es.name for es in service.schema.entity_sets]

Property has this label

assert client.schema.entity_type('Customer').proprty('CustomerID').label == 'Identifier'

Property has a value helper

assert client.schema.entity_type('Customer').proprty('City').value_helper is not None