GQLAlchemy is library developed with purpose of assisting writing and running queries on Memgraph.
Project description
GQLAlchemy
GQLAlchemy is a fully open-source Python library and Object Graph Mapper (OGM) - a link between graph database objects and Python objects.
An Object Graph Mapper or OGM provides a developer-friendly workflow that allows for writing object-oriented notation to communicate with graph databases. Instead of writing Cypher queries, you will be able to write object-oriented code, which the OGM will automatically translate into Cypher queries.
GQLAlchemy is built on top of Memgraph's low-level Python client pymgclient
(PyPI /
Documentation /
GitHub).
Installation
Before you install gqlalchemy
, make sure that you have cmake
installed by running:
cmake --version
You can install cmake
by following the official instructions.
To install gqlalchemy
, simply run the following command:
pip install gqlalchemy
Build & Test
The project uses Poetry to build the GQLAlchemy Python library. To build and run tests, execute the following command:
poetry install
Before starting the tests, make sure you have an active Memgraph instance running. Execute the following command:
poetry run pytest .
GQLAlchemy example
When working with the gqlalchemy
, a Python developer can connect to the database and execute a MATCH
Cypher query using the following syntax:
from gqlalchemy import Memgraph
memgraph = Memgraph("127.0.0.1", 7687)
memgraph.execute("CREATE (:Node)-[:Connection]->(:Node)")
results = memgraph.execute_and_fetch("""
MATCH (from:Node)-[:Connection]->(to:Node)
RETURN from, to;
""")
for result in results:
print(result['from'])
print(result['to'])
Query builder example
As we can see, the example above can be error-prone, because we do not have abstractions for creating a database connection and MATCH
query.
Now, rewrite the exact same query by using the functionality of GQLAlchemy's query builder:
from gqlalchemy import match, Memgraph
memgraph = Memgraph()
results = (
match()
.node("Node", variable="from")
.to("Connection")
.node("Node", variable="to")
.return_()
.execute()
)
for result in results:
print(result["from"])
print(result["to"])
An example using the Node
and Relationship
classes:
from gqlalchemy import Memgraph, Node, Relationship, match, Field
memgraph = Memgraph("127.0.0.1", 7687)
class User(Node):
id: int = Field(index=True, exist=True, unique=True, db=memgraph)
class Follows(Relationship, type="FOLLOWS"):
pass
u1 = User(id=1).save(memgraph)
u2 = User(id=2).save(memgraph)
r = Follows(_start_node_id=u1._id, _end_node_id=u2._id).save(memgraph)
result = list(
match(memgraph.new_connection())
.node(variable="a")
.to(variable="r")
.node(variable="b")
.where("a.id", "=", u1.id)
.or_where("b.id", "=", u2.id)
.return_()
.execute()
)[0]
print(result["a"])
print(result["b"])
print(result["r"])
Development (how to build)
poetry run flake8 .
poetry run black .
poetry run pytest . -k "not slow"
Documentation
The GQLAlchemy documentation is available on memgraph.com/docs/gqlalchemy.
The documentation can be generated by executing:
pip3 install python-markdown
python-markdown
License
Copyright (c) 2016-2022 Memgraph Ltd.
Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.
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