python-epo-ops-client 0.1.2

Python Client for the European Patent Office's Open Patent Services API

# python-epo-ops-client

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python-epo-ops-client is an [Apache2 Licensed][Apache license] client library
for accessing the [European Patent Office][EPO]'s ("EPO")
[Open Patent Services][OPS] ("OPS") v.3.1 (based on
[v 1.2.10 of the reference guide][OPS guide]).

```python
import epo_ops

anonymous_client = epo_ops.Client() # Instantiate a default client
response = anonymous_client.published_data( # Retrieve bibliography data
reference_type = 'publication', # publication, application, priority
input = epo_ops.models.Docdb('1000000', 'EP', 'A1'), # original, docdb, epodoc
endpoint = 'biblio', # optional, defaults to biblio in case of published_data
constituents = [] # optional, list of constituents
)

registered_client = epo_ops.RegisteredClient(key='abc', secret='xyz')
registered_client.access_token # To see the current token
response = registered_client.published_data(…)
```

---

## Features

python_epo_ops_client abstracts away the complexities of access EPO OPS:

* Format the requests properly
* Bubble up quota problems as proper HTTP errors
* Handle token authentication and renewals automatically
* Handle throttling properly
* Add optional caching to minimize impact on the OPS servers

There are two main layers to python_epo_ops_client: Client and Middleware.
Storage.

### Client

The Client contains all the formatting and token handling logic. The Client
class is what you'll interact with mostly.

When you issue a request, the response is a
[`requests.Response`][requests.Response] object. If `response.status_code !=
200` then an exception will be raised, it's your responsibility to handle those
exceptions if you want to. The one case that's handled by the RegisteredClient
is when its access token has expired: in this case, the client will
automatically handle the HTTP 400 status and renew the token.

Note that the Client does not attempt to interpret the data supplied by OPS, so
it's your responsibility to parse the XML or JSON payload for your own purpose.

The following custom exceptions are raised for cases when OPS quotas are
exceeded, they are all subclasses of `requests.HTTPError` and offer the same
behavior:

* AnonymousQuotaPerMinuteExceeded
* AnonymousQuotaPerDayExceeded
* IndividualQuotaPerHourExceeded
* RegisteredQuotaPerWeekExceeded

Again, it's up to you to parse the response and decide what to do.

Currently the Client only knows how to issue request for the following
services:

* /published-data/search (search)
* /published-data (retrieval)
* /family (inpadoc)

Please submit pull requests for other services by enhancing the
`epo_ops.api.Client` class.

### Middleware

All requests and responses are passed through each middleware object listed in
`client.middlewares`. Requests are processed in the order listed, and responses
are processed in the *reverse* order.

Each middleware should subclass `middlewares.Middleware` and implement the
`process_request` and `process_response` methods.

There are two middleware classes out of the box: Throttler and Dogpile.
Throttler is in charge of the OPS throttling rules and will delay requests
accordingly. Dogpile is an optional cache which will cache all HTTP status 200,
404, 405, and 413 responses.

By default, only the Throttler middleware is enabled, if you want to enable
caching:

```python
import epo_ops

middlewares = [
epo_ops.middlewares.Dogpile(),
epo_ops.middlewares.Throttler(),
]
registered_client = epo_ops.RegisteredClient(
key='key',
secret='secret',
middlewares=middlewares,
)
```

*Note that caching middleware should be first in most cases.*

#### Dogpile

Dogpile is based on (surprise) [dogpile.cache][]. By default it is instantiated
with a DBMBackend region with timeout of 2 weeks.

Dogpile takes three optional instantiation parameters:

* `region`: You can pass whatever valid [dogpile.cache Region][] you want to
backend the cache
* `kwargs_handlers`: A list of keyword argument handlers, which it will use to
process the kwargs passed to the request object in order to extract elements
for generating the cache key. Currently one handler is implemented (and
instantiated by default) to make sure that the X-OPS-Range request header
is part of the cache key.
* `http_status_codes`: A list of HTTP status codes that you would like to have
cached. By default 200, 404, 405, and 413 responses are cached.

**Note**: dogpile.cache is not installed by default, if you want to use it,
`pip install dogpile.cache` in your project.

#### Throttler

Throttler contains all the logic for handling different throttling scenarios.
Since OPS throttling is based on a one minute rolling window, we must persist
historical (at least for the past minute) throtting data in order to know what
the proper request frequency is. Each Throttler must be instantiated with a
Storage object.

##### Storage

The Storage object is responsible for:

1. Knowing how to update the historical record with each request
(`Storage.update()`), making sure to observe the one minute rolling window
rule.
2. Calculating how long to wait before issuing the next request
(`Storage.delay_for()`).

Currently the only Storage backend provided is SQLite, but you can easily write
your own Storage backend (such as file, Redis, etc.). To use a custom Storage
type, just pass the Storage object when you're instantiating a Throttler
object. See `epo_ops.middlewares.throttle.storages.Storage` for more
implementation details.

---

## Tests

Tests are written using [pytest][]. To run the tests:

1. [Register a OPS user login with EPO][OPS registration]
2. Create an app
3. Set the `OPS_KEY` and `OPS_SECRET` environment variables accordingly
4. `make test`

The tests must be run with a working internet connection, since both OPS and
the [mock Apiary services][Apiary OPS] are online.


[EPO]: http://epo.org
[OPS]: http://www.epo.org/searching/free/ops.html
[OPS registration]: https://developers.epo.org/user/register
[OPS guide]: http://documents.epo.org/projects/babylon/eponet.nsf/0/7AF8F1D2B36F3056C1257C04002E0AD6/$File/OPS_RWS_ReferenceGuide_version1210_EN.pdf
[Requests]: http://requests.readthedocs.org/en/latest/
[requests.Response]: http://requests.readthedocs.org/en/latest/user/advanced/#request-and-response-objects
[pytest]: http://pytest.org/latest/
[Apiary OPS]: http://docs.opsv31.apiary.io
[Apache license]: http://www.apache.org/licenses/LICENSE-2.0
[dogpile.cache]: https://bitbucket.org/zzzeek/dogpile.cache
[dogpile.cache Region]: http://dogpilecache.readthedocs.org/en/latest/api.html#module-dogpile.cache.region


# Release History

## 0.1.2 (2014-03-04)

* Python 2.6 and 3.3 compatibility

## 0.1.1 (2014-03-01)

* Allow configuration of which HTTP responses (based on status code) to cache

## 0.1.0 (2014-02-20)

* Introduced dogpile.cache for caching http200 resopnses
* Introduced the concept of middleware

## 0.0.1 (2014-01-21)

* Initial release