mygraph-client (Python)

Python client for the MyGraph server. It talks to the server over TCP using MyGraph protocol v1 (docs/PROTOCOL.md) and needs only the standard library (Python ≥ 3.10).

Install

pip install mygraph-client

The import name is mygraph:

import mygraph

For development, from the repository root:

pip install -e python/

Start a server

cargo run -p mygraph-server -- start                      # 127.0.0.1:6660, in memory
cargo run -p mygraph-server -- start --port 6660 --data ./data

Command line client

pip install also installs the mygraph-client command. With a server on port 6660 (for example docker compose up -d):

mygraph-client "MATCH (n) RETURN n;"

n
(0:User {"age": 25, "name": "Alice"})
(1:User {"name": "Bob"})

Without a query argument the script is read from stdin, so multi-line queries work too:

mygraph-client <<'CYPHER'
MATCH (n)
RETURN n;
CYPHER

Without installing, python3 -m mygraph does the same. On error it prints the message to stderr and exits with status 1.

Usage

import mygraph

with mygraph.connect("localhost", 6660) as db:
    # Any Cypher, with parameters as a dict and/or keyword arguments
    r = db.run("MATCH (u:User) WHERE u.age > $min RETURN u.name AS name", min=18)
    for record in r:                # records are dicts
        print(record["name"])
    r.value("name"); r.values("name"); r.single(); r.stats.nodes_created

    # Create
    alice = db.create_node("User", {"name": "Alice", "age": 25})          # -> Node
    bob = db.create_node(["User", "Admin"], {"name": "Bob"})
    knows = db.create_relationship(alice.id, bob.id, "KNOWS", {"since": 2020})

    # Search
    db.get_node(alice.id)                                                 # Node | None
    db.find_nodes("User", {"name": "Alice"}, order_by="age", limit=10)    # list[Node]
    db.count_nodes("User")
    db.find_relationships("KNOWS", start_id=alice.id)                     # list[Relationship]

    # Update
    db.update_node(alice.id, {"age": 26})                  # merge: SET n += $props (None removes a key)
    db.update_node(alice.id, {"name": "Alicia"}, replace=True)   # SET n = $props
    db.update_node(alice.id, add_labels="VIP", remove_labels="Admin")
    db.update_relationship(knows.id, {"since": 2021})

    # Delete
    db.delete_relationship(knows.id)
    db.delete_node(alice.id)                      # DETACH DELETE by default
    db.delete_nodes("User", {"name": "Bob"})     # returns how many

    # Transactions: commit on exit, rollback on exception
    with db.transaction() as tx:
        tx.create_node("User", {"name": "Carol"})
        tx.run("MATCH (u:User {name: 'Carol'}) SET u.vip = true")

    # Databases and schemas (the current one is per connection)
    db.create_database("shop"); db.use_database("shop"); db.databases()

Node has id, labels, properties (and node["key"]). Relationship has id, start_node, end_node, type, properties.

Helpers write labels, types and property keys as backtick-quoted identifiers, and always send values as parameters, so user input is never spliced into the query text.

Errors

An error in a statement does not close the connection.

Notes for MyGraph v0.1

• An open transaction blocks every other connection until it commits or rolls back. Keep transactions short.
• While a transaction is open, everything sent on that client runs inside it.
• A client serializes its requests with a lock. Threads that share one client also share its current database and transaction, so use one client per thread for independent work.
• AUTH is accepted but not checked yet (no users or roles on the server).

Tests

cd python
python3 -m unittest discover -s tests -t .

The integration tests build mygraph-server with cargo and start it on a free port. Set MYGRAPH_SERVER_BIN to use an existing binary instead.