Build applications with Neo4j and Python
Connect to the database
Connect to a database by creating a Driver object and providing a URL and an authentication token.
Once you have a Driver
instance, use the .verify_connectivity()
method to ensure that a working connection can be established.
from neo4j import GraphDatabase
# URI examples: "neo4j://localhost", "neo4j+s://xxx.databases.neo4j.io"
URI = "<URI for Neo4j database>"
AUTH = ("<Username>", "<Password>")
with GraphDatabase.driver(URI, auth=AUTH) as driver:
driver.verify_connectivity()
Query the database
Execute a Cypher statement by creating a session and using the methods Session.execute_read()
and Session.execute_write()
.
Do not hardcode or concatenate parameters: use placeholders and specify the parameters as keyword arguments.
def match_person_nodes(tx, age):
result = tx.run(
"MATCH (p:Person {age: $age}) RETURN p.name AS name",
age=age)
records = list(result)
summary = result.consume()
return records, summary
with driver.session(database="neo4j") as session:
records, summary = session.execute_read(match_person_nodes, age=42)
# Summary information
print("The query `{query}` returned {records_count} records in {time} ms.".format(
query=summary.query, records_count=len(records),
time=summary.result_available_after,
))
# Loop through results and do something with them
for person in records:
print(person)
Close connections and sessions
Unless you created them using the with
statement, call the .close()
method on all Driver
and Session
instances to release any resources still held by them.
session.close()
driver.close()
Glossary
- LTS
-
A Long Term Support release is one guaranteed to be supported for a number of years. Neo4j 4.4 is LTS, and Neo4j 5 will also have an LTS version.
- Aura
-
Aura is Neo4j’s fully managed cloud service. It comes with both free and paid plans.
- Driver
-
A
Driver
object holds the details required to establish connections with a Neo4j database. Every Neo4j-backed application requires aDriver
object. - Cypher
-
Cypher is Neo4j’s graph query language that lets you retrieve data from the graph. It is like SQL, but for graphs.
- APOC
-
Awesome Procedures On Cypher (APOC) is a library of (many) functions that can not be easily expressed in Cypher itself.
- Bolt
-
Bolt is the protocol used for interaction between Neo4j instances and drivers. It listens on port 7687 by default.
- ACID
-
Atomicity, Consistency, Isolation, Durability (ACID) are properties guaranteeing that database transactions are processed reliably. An ACID-compliant DBMS ensures that the data in the database remains accurate and consistent despite failures.
- eventual consistency
-
A database is eventually consistent if it provides the guarantee that all cluster members will, at some point in time, store the latest version of the data.
- causal consistency
-
A database is causally consistent if read and write queries are seen by every member of the cluster in the same order. This is stronger than eventual consistency.
- null
-
The null marker is not a type but a placeholder for absence of value. For more information, see Cypher Manual — Working with
null
. - transaction
-
A transaction is a unit of work that is either committed in its entirety or rolled back on failure. An example is a bank transfer: it involves multiple steps, but they must all succeed or be reverted, to avoid money being subtracted from one account but not added to the other.
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