Mercurial > hg > orthanc-book
diff Sphinx/source/plugins/python.rst @ 469:46949efa5818
Implementing basic paging using a Python script
author | Sebastien Jodogne <s.jodogne@gmail.com> |
---|---|
date | Tue, 04 Aug 2020 16:42:11 +0200 |
parents | fcc352fd4283 |
children | 03dfb896ca4b |
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--- a/Sphinx/source/plugins/python.rst Mon Jul 27 16:57:13 2020 +0200 +++ b/Sphinx/source/plugins/python.rst Tue Aug 04 16:42:11 2020 +0200 @@ -240,6 +240,8 @@ $ curl http://localhost:8042/toto ok + +.. _python-changes: Listening to changes .................... @@ -556,7 +558,7 @@ about `attribute matching <http://dicom.nema.org/medical/dicom/2019e/output/chtml/part04/sect_C.2.2.2.html>`__. -.. highlight:: python +.. highlight:: bash Here is a sample call to retrieve all the studies that were last updated in 2019 thanks to this Python script:: @@ -564,6 +566,82 @@ $ curl http://localhost:8042/tools/find -d '{"Level":"Study","Query":{},"Expand":true,"Metadata":{"LastUpdate":"^2019.*$"}}' +.. _python-paging: + +Implementing basic paging +......................... + +.. highlight:: python + +As explained in the FAQ, the :ref:`Orthanc Explorer interface is +low-level <improving-interface>`, and is not adapted for +end-users. One common need is to implement paging of studies, which +calls for server-side sorting of studies. This can be done using the +following sample Python plugin that registers a new route +``/sort-studies`` in the REST API of Orthanc:: + + import json + import orthanc + + def GetStudyDate(study): + if 'StudyDate' in study['MainDicomTags']: + return study['MainDicomTags']['StudyDate'] + else: + return '' + + def SortStudiesByDate(output, uri, **request): + if request['method'] == 'GET': + # Retrieve all the studies + studies = json.loads(orthanc.RestApiGet('/studies?expand')) + + # Sort the studies according to the "StudyDate" DICOM tag + studies = sorted(studies, key = GetStudyDate) + + # Read the limit/offset arguments provided by the user + offset = 0 + if 'offset' in request['get']: + offset = int(request['get']['offset']) + + limit = 0 + if 'limit' in request['get']: + limit = int(request['get']['limit']) + + # Truncate the list of studies + if limit == 0: + studies = studies[offset : ] + else: + studies = studies[offset : offset + limit] + + # Return the truncated list of studies + output.AnswerBuffer(json.dumps(studies), 'application/json') + else: + output.SendMethodNotAllowed('GET') + + orthanc.RegisterRestCallback('/sort-studies', SortStudiesByDate) + + +.. highlight:: bash + +Here is a sample call to this new REST route, that could be issued by +any JavaScript framework (the ``json_pp`` command-line pretty-prints a +JSON file):: + + $ curl http://localhost:8042/sort-studies | json_pp + +This route also implement paging (i.e. it can limit and offset the +returned studies):: + + $ curl 'http://localhost:8042/sort-studies?offset=2&limit=2' | json_pp + +Obviously, this basic sample can be improved in many ways. To improve +performance, one could for instance cache the result of +``/studies?expand`` in memory by :ref:`listening to changes +<python-changes>` in the list of studies +(cf. ``orthanc.ChangeType.NEW_STUDY`` and +``orthanc.ChangeType.DELETED``). + + + Performance and concurrency ---------------------------