PyXero

PyXero is a Python API for accessing the REST API provided by the Xero accounting tool. It allows access to both Public, Private and Partner applications.

This code is based off the sample code provided by Xero, which was contributed by IRESS Wealth Management, and the XeroPy packaged version of that code.

This packages differs in three significant was from XeroPy:

• It uses the popular requests library (and the requests-oauthlib extension) instead of httplib2.
• It uses the pure-python PyCrypto library instead of the hard-to-compile native M2Crypto wrapper for RSA signing.
• It has been tested on both Public and Private Xero Applications.

Quickstart:

In addition to the instructions shown here, you'll need to follow the Xero Developer documentation to register your application.

Public Applications

Public applications use a 3-step OAuth process.

When you register your public application with Xero, you'll be given a Consumer Key and a Consumer secret. These are both strings.

To access the Xero API you must first create some credentials:

>>> from xero.auth import PublicCredentials
>>> credentials = PublicCredentials(<consumer_key>, <consumer_secret>)
>>> print credentials.url
'http://my.xero.com/.....'

You now direct the user to visit the URL described by credentials.url. They will be asked to log into their Xero account, and then shown a request to authenticate your request to access the user's account. When the allow access, they will be directed to a page that gives them a 6-digit verification number. Put this verifier number into a string, and call verify() on the credentials object::

>>> credentials.verify(<verifier string>)

This will verify your credentials, and retrieve an access token. You can then use your credentials to instantiate an instance of the Xero API::

>>> from xero import Xero
>>> xero = Xero(credentials)

Public Applications with verification by callback

Public applications can also be validated using a callback URI. If this approach is used, the user won't be given a verification number. Instead, when they authorize the OAuth request, their browser will be redirected to a pre-configured callback URI, which will deliver the validation token directly to your application.

To use a callback, you must provide a domain as part of your Xero application registration; then, you provide a URL under that domain as the third argument when creating the credentials::

>>> credentials = PublicCredentials(<consumer_key>, <consumer_secret>, <callback_uri>)
>>> print credentials.url
'http://my.xero.com/.....'

When the user authorizes access to their Xero account, the callback_url will be called with three GET arguments:

• oauth_token: The oauth_token that this request belongs to
• verifier: The verifier string
• org: An identifier for the organization that is allowing access.

The verifier can then be used to verify the credentials, as with the manual process.

Reconstructing Public credentials

Public Applications use a 3-step OAuth process, and if you're doing this in a web application, you will usually lose the credentials object over the verification step. This means you need to be able to restore the credentials object when verification has been provided.

The state attribute of a credentials object contains all the details needed to reconstruct an instance of the credentials::

>>> saved_state = credentials.state
>>> print saved_state
{'consumer_key': '...', 'consumer_secret': '...', ...}

>>> new_credentials = PublicCredentials(**saved_state)

Private Applications

If using a Private application, you will need to install PyCrypto, a pure Python cryptographic module. You'll also need to generate an signed RSA certificate, and submit that certificate as part of registering your application with Xero. See the Xero Developer documentation for more details.

When you register your private application with Xero, you'll be given a Consumer Key. You'll also be given a Consumer secret - this can be ignored.

Using the Private credentials is much simpler than the Public credentials, because there's no verification step -- verification is managed using RSA signed API requests::

>>> from xero import Xero
>>> from xero.auth import PrivateCredentials
>>> with open(<path to rsa key file>) as keyfile:
...     rsa_key = keyfile.read()
>>> credentials = PrivateCredentials(<consumer_key>, rsa_key)
>>> xero = Xero(credentials)

The RSA key is a multi-line string that will look something like::

-----BEGIN RSA PRIVATE KEY-----
MIICXgIBAAKBgQDWJbmxJjQLGM76sZkk2EhsdpV0Gxtrhzh/wiNBGffa5JHV/Ex4
....
mtXGQjKqsOpuCw7HwgnRQUWKYbaJ3a+yTCFjVwa9keQhDQ==
-----END RSA PRIVATE KEY-----

You can get this string by either reading the contents of your private key file into a variable, or storing the key value as a constant. If you choose to store the key value as a constant, remember two things:

• DO NOT UNDER ANY CIRCUMSTANCES check this file into a public repository. It is your identity, and anyone with access to this file could masquerade as you.

• Make sure there is no leading space before the -----BEGIN PRIVATE KEY----- portion of the string.

Partner Applications

Partner Application authentication works similarly to the 3-step OAuth used by Public Applications, but with RSA signed requests and a client-side SSL certificate which is issued by Xero. Partner OAuth tokens still have a 30 minute expiry, but can be swapped for a new token at any time.

When you register your partner application with Xero, you'll have a Consumer Key, Consumer Secret, RSA Key, and Client Certificate. All four elements are required.

The client certificate is represented by a tuple of file paths to the certificate and key.

>>> from xero import Xero
>>> from xero.auth import PartnerCredentials
>>> client_cert = ('/path/to/entrust-cert.pem',
...                '/path/to/entrust-private-nopass.pem')
>>> credentials = PartnerCredentials(<consumer_key>, <consumer_secret>,
...                                  <rsa_key>, client_cert)
>>> xero = Xero(credentials)

When using the API over an extended period, you will need to exchange tokens when they expire.

>>> if credentials.expired():
...     credentials.refresh()

Important: credentials.state changes after a token swap. Be sure to persist the new state.

Using the Xero API

This API is a work in progress. At present, there is no wrapper layer to help create real objects, it just returns dictionaries in the exact format provided by the Xero API. This will change into a more useful API before 1.0

The Xero API object exposes a simple API for retrieving and updating objects. For example, to deal with contacts::

# Retrieve all contact objects
>>> xero.contacts.all()
[{...contact info...}, {...contact info...}, {...contact info...}, ...]

# Retrieve a specific contact object
>>> xero.contacts.get(u'b2b5333a-2546-4975-891f-d71a8a640d23')
{...contact info...}

# Retrive all contacts updated since 1 Jan 2013
>>> xero.contacts.filter(since=datetime(2013, 1, 1))
[{...contact info...}, {...contact info...}, {...contact info...}]

# Retrive all contacts whose name is 'John Smith'
>>> xero.contacts.filter(Name='John Smith')
[{...contact info...}, {...contact info...}, {...contact info...}]

# Retrive all contacts whose name starts with 'John'
>>> xero.contacts.filter(Name__startswith='John')
[{...contact info...}, {...contact info...}, {...contact info...}]

# Retrive all contacts whose name ends with 'Smith'
>>> xero.contacts.filter(Name__endswith='Smith')
[{...contact info...}, {...contact info...}, {...contact info...}]

# Retrive all contacts whose name starts with 'John' and ends with 'Smith'
>>> xero.contacts.filter(Name__startswith='John', Name__endswith='Smith')
[{...contact info...}, {...contact info...}, {...contact info...}]

# Retrive all contacts whose name contains 'mit'
>>> xero.contacts.filter(Name__contains='mit')
[{...contact info...}, {...contact info...}, {...contact info...}]

# Create a new object
>>> xero.contacts.put({...contact info...})

# Create a new object
>>> xero.contacts.put([{...contact info...}, {...contact info...}, {...contact info...}])

# Save an update to an existing object
>>> c = xero.contacts.get(u'b2b5333a-2546-4975-891f-d71a8a640d23')
>>> c['Name'] = 'John Smith'
>>> xero.contacts.save(c)

# Save multiple objects
>>> xero.contacts.save([c1, c2])

Complex filters can be constructed in the Django-way, for example retrieving invoices for a contact::

>>> xero.invoices.filter(Contact_ContactID='83ad77d8-48a7-4f77-9146-e6933b7fb63b')

Be careful when dealing with large amounts of data, the Xero API will take an increasingly long time to respond, or an error will be returned. If a query might return more than 100 results, you should make use of the page parameter::

# Grab 100 invoices created after 01-01-2013
>>> xero.invoices.filter(since=datetime(2013, 1, 1), page=1)

You can also order the results to be returned::

# Grab contacts ordered by EmailAddress
>>> xero.contacts.filter(order='EmailAddress DESC')

For invoices (and other objects that can be retrieved as PDFs), accessing the PDF is done via setting the Accept header:

# Fetch a PDF
invoice = xero.invoices.get('af722e93-b64f-482d-9955-1b027bfec896', \
    headers={'Accept': 'application/pdf'})
# Stream the PDF to the user (Django specific example)
response = HttpResponse(invoice, content_type='application/pdf')
response['Content-Disposition'] = 'attachment; filename="invoice.pdf"'
return response

Download and uploading attachments is supported using the Xero GUID of the relevant object::

# List attachments on a contact
>>> xero.contacts.get_attachments(c['ContactID'])
[{...attachment info...}, {...attachment info...}]

# Attach a PDF to a contact
>>> f = open('form.pdf', 'rb')
>>> xero.contacts.put_attachment(c['ContactID'], 'form.pdf', f, 'application/pdf')
>>> f.close()

>>> xero.contacts.put_attachment_data(c['ContactID'], 'form.pdf', data, 'application/pdf')

# Download an attachment
>>> f = open('form.pdf', 'wb')
>>> xero.contacts.get_attachment(c['ContactID'], 'form.pdf', f)
>>> f.close()

>>> data = xero.contacts.get_attachment_data(c['ContactID'], 'form.pdf')

This same API pattern exists for the following API objects:

• Accounts
• Contacts
• CreditNotes
• Currencies
• Invoices
• Organisation
• Payments
• TaxRates
• TrackingCategories
• ManualJournals
• BankTransactions
• BankTransfers

Contributing

If you're going to run the PyXero test suite, in addition to the dependencies for PyXero, you need to add the following dependency to your environment:

mock >= 1.0

Mock isn't included in the formal dependencies because they aren't required for normal operation of PyXero. It's only required for testing purposes.

Once you've installed these dependencies, you can run the test suite by running the following from the root directory of the project:

$ python setup.py test

If you find any problems with pyxero, you can log them on Github Issues. When reporting problems, it's extremely helpful if you can provide reproduction instructions -- the sequence of calls and/or test data that can be used to reproduce the issue.

New features or bug fixes can be submitted via a pull request. If you want your pull request to be merged quickly, make sure you either include regression test(s) for the behavior you are adding/fixing, or provide a good explanation of why a regression test isn't possible.