Metadata-Version: 2.0
Name: pydgraph
Version: 1.0.0
Summary: Official Dgraph client implementation for Python
Home-page: https://github.com/dgraph-io/pydgraph
Author: Dgraph Labs
Author-email: contact@dgraph.io
License: Apache License, Version 2.0
Description-Content-Type: UNKNOWN
Platform: UNKNOWN
Classifier: Intended Audience :: Developers
Classifier: License :: OSI Approved :: Apache Software License
Classifier: Operating System :: OS Independent
Classifier: Topic :: Database
Classifier: Topic :: Software Development
Classifier: Programming Language :: Python :: 2.7
Classifier: Programming Language :: Python :: 3.5
Classifier: Programming Language :: Python :: 3.6
Requires-Dist: grpcio (==1.10.0)

pydgraph `Build Status <https://travis-ci.org/dgraph-io/pydgraph>`__ `Coverage Status <https://coveralls.io/github/dgraph-io/pydgraph?branch=master>`__
=======================================================================================================================================================

Official Dgraph client implementation for Python (Python >= v2.7 and >=
v3.5), using `grpc <https://grpc.io/>`__.

This client follows the `Dgraph Go
client <https://github.com/dgraph-io/dgo>`__ closely.

Before using this client, we highly recommend that you go through
`docs.dgraph.io <https://docs.dgraph.io>`__, and understand how to run
and work with Dgraph.

Table of contents
-----------------

-  `Install <#install>`__
-  `Quickstart <#quickstart>`__
-  `Using a client <#using-a-client>`__

   -  `Create a client <#create-a-client>`__
   -  `Alter the database <#alter-the-database>`__
   -  `Create a transaction <#create-a-transaction>`__
   -  `Run a mutation <#run-a-mutation>`__
   -  `Run a query <#run-a-query>`__
   -  `Commit a transaction <#commit-a-transaction>`__
   -  `Cleanup Resources <#cleanup-resources>`__

-  `Development <#development>`__

   -  `Building the source <#building-the-source>`__
   -  `Running tests <#running-tests>`__

Install
-------

Install using pip:

.. code:: sh

   pip install pydgraph

Quickstart
----------

Build and run the
`simple <https://github.com/dgraph-io/pydgraph/tree/master/examples/simple>`__
project in the ``examples`` folder, which contains an end-to-end example
of using the Dgraph python client. Follow the instructions in the README
of that project.

Using a client
--------------

Create a client
~~~~~~~~~~~~~~~

A ``DgraphClient`` object can be initialised by passing it a list of
``DgraphClientStub`` clients as variadic arguments. Connecting to
multiple Dgraph servers in the same cluster allows for better
distribution of workload.

The following code snippet shows just one connection.

.. code:: python

   import pydgraph

   client_stub = pydgraph.DgraphClientStub('localhost:9080')
   client = pydgraph.DgraphClient(client_stub)

Alter the database
~~~~~~~~~~~~~~~~~~

To set the schema, create an ``Operation`` object, set the schema and
pass it to ``DgraphClient#alter(Operation)`` method.

.. code:: python

   schema = 'name: string @index(exact) .'
   op = pydgraph.Operation(schema=schema)
   client.alter(op)

``Operation`` contains other fields as well, including drop predicate
and drop all. Drop all is useful if you wish to discard all the data,
and start from a clean slate, without bringing the instance down.

.. code:: python

   # Drop all data including schema from the Dgraph instance. This is useful
   # for small examples such as this, since it puts Dgraph into a clean
   # state.
   op = pydgraph.Operation(drop_all=True)
   client.alter(op)

Create a transaction
~~~~~~~~~~~~~~~~~~~~

To create a transaction, call ``DgraphClient#txn()`` method, which
returns a new ``Txn`` object. This operation incurs no network overhead.

It is good practise to call ``Txn#discard()`` in a ``finally`` block
after running the transaction. Calling ``Txn#discard()`` after
``Txn#commit()`` is a no-op and you can call ``Txn#discard()`` multiple
times with no additional side-effects.

.. code:: python

   txn = client.txn()
   try:
     # Do something here
     # ...
   finally:
     txn.discard()
     # ...

Run a mutation
~~~~~~~~~~~~~~

``Txn#mutate(mu=Mutation)`` runs a mutation. It takes in a ``Mutation``
object, which provides two main ways to set data: JSON and RDF N-Quad.
You can choose whichever way is convenient. Most users won’t need to
create a ``Mutation`` object themselves.

``Txn#mutate()`` provides convenience keyword arguments ``set_obj`` and
``del_obj`` for setting JSON values and ``set_nquads`` and
``del_nquads`` for setting N-Quad values. See examples below for usage.

We define a person object to represent a person and use it in a
transaction.

.. code:: python

   # Create data.
   p = {
       'name': 'Alice',
   }

   # Run mutation.
   txn.mutate(set_obj=p)

   # If you want to use a mutation object, use this instead:
   # mu = pydgraph.Mutation(set_json=json.dumps(p).encode('utf8'))
   # txn.mutate(mu)

   # If you want to use N-Quads, use this instead:
   # txn.mutate(set_nquads='_:alice <name> "Alice"')

For a more complete example with multiple fields and relationships, look
at the
`simple <https://github.com/dgraph-io/pydgraph/tree/master/examples/simple>`__
project in the ``examples`` folder.

Sometimes, you only want to commit a mutation, without querying anything
further. In such cases, you can set the keyword argument
``commit_now=True`` to indicate that the mutation must be immediately
committed.

Keyword argument ``ignore_index_conflict=True`` can be used to not run
conflict detection over the index, which would decrease the number of
transaction conflicts and aborts. However, this would come at the cost
of potentially inconsistent upsert operations.

Run a query
~~~~~~~~~~~

You can run a query by calling ``Txn#query(string)``. You will need to
pass in a GraphQL+- query string. If you want to pass an additional
dictionary of any variables that you might want to set in the query,
call ``Txn#query(string, variables=d)`` with the variables dictionary
``d``.

The response would contain the field ``json``, which returns the
response JSON.

Let’s run the following query with a variable $a:

.. code:: console

   query all($a: string) {
     all(func: eq(name, $a))
     {
       name
     }
   }

Run the query, deserialize the result from JSON and print it out:

.. code:: python

   # Run query.
   query = """query all($a: string) {
     all(func: eq(name, $a))
     {
       name
     }
   }"""
   variables = {'$a': 'Alice'}

   res = client.txn().query(query, variables=variables)
   # If not doing a mutation in the same transaction, simply use:
   # res = client.query(query, variables=variables)

   ppl = json.loads(res.json);

   # Print results.
   print('Number of people named "Alice": {}'.format(len(ppl['all'])))
   for person in ppl['all']:
     print(person)

This should print:

.. code:: console

   Number of people named "Alice": 1
   Alice

Commit a transaction
~~~~~~~~~~~~~~~~~~~~

A transaction can be committed using the ``Txn#commit()`` method. If
your transaction consisted solely of calls to ``Txn#query`` or
``Txn#queryWithVars``, and no calls to ``Txn#mutate``, then calling
``Txn#commit()`` is not necessary.

An error will be raised if other transactions running concurrently
modify the same data that was modified in this transaction. It is up to
the user to retry transactions when they fail.

.. code:: python

   txn = client.txn();
   try:
     # ...
     # Perform any number of queries and mutations
     # ...
     # and finally...
     txn.commit()
   except Exception as e:
     if isinstance(e, pydgraph.AbortedError):
       # Retry or handle exception.
     else:
       raise e
   finally:
     # Clean up. Calling this after txn.commit() is a no-op
     # and hence safe.
     txn.discard()

Cleanup Resources
~~~~~~~~~~~~~~~~~

To cleanup resources, you have to call ``DgraphClientStub#close()``
individually for all the instances of ``DgraphClientStub``.

.. code:: python

   SERVER_ADDR = "localhost:9080"

   # Create instances of DgraphClientStub.
   stub1 = pydgraph.DgraphClientStub(SERVER_ADDR)
   stub2 = pydgraph.DgraphClientStub(SERVER_ADDR)

   # Create an instance of DgraphClient.
   client = pydgraph.DgraphClient(stub1, stub2)

   # ...
   # Use client
   # ...

   # Cleanup resources by closing all client stubs.
   stub1.close()
   stub2.close()

Development
-----------

Building the source
~~~~~~~~~~~~~~~~~~~

.. code:: sh

   python setup.py install
   # To install for the current user, use this instead:
   # python setup.py install --user

If you have made changes to the ``pydgraph/proto/api.proto`` file, you
need need to regenerate the source files generated by Protocol Buffer
tools. To do that, install the
`grpcio-tools <https://pypi.python.org/pypi/grpcio-tools>`__ library and
then run the following command:

.. code:: sh

   python scripts/protogen.py

Running tests
~~~~~~~~~~~~~

Make sure you have a Dgraph server running on localhost before you run
this task.

.. code:: sh

   python setup.py test


