GraphAcademy

Using Neo4j with Python

The Driver

Handling results

Best practices

Transaction functions

You have built an application that streams the results of a long-running Cypher statement to the client.

You have written a transaction function called get_cheapest_flights to execute a read query within a transaction.

View the get_cheapest_flights function
python
def get_cheapest_flights(tx, date, origin, destination):
    """
    Return the cheapest flights between the origin and
    destination airports on a given date.
    """
    result = tx.run("""
        MATCH (origin:Airport)<-[:ORIGIN]-(f:Flight)-[:DESTINATION]->(destination:Airport),
            (f)-[:OPERATED_BY]->(operator:Airline)
        WHERE origin.name = $origin AND destination.name = $destination AND f.date = $date
        RETURN f.price AS price, operator.name AS operator
    """, date=date, origin=origin, destination=destination)
    return result.values()

The application then uses an external function called send_to_ui to send the results to the client.

Read transactions

Select the correct function to execute the Cypher statement in a read transaction and stream the results to the client as soon as they are available.

python
from api import send_to_ui


with driver.session() as session:
    res = session.#select:execute_read(
        get_cheapest_flights,
        date="2024-01-01",
        origin="LAX",
        destination="SFO"
    )

    for row in res:
        send_to_ui(row)

  • ❏ cypher(

  • ✓ execute_read(

  • ❏ execute_write(

  • ❏ run_async(

Hint

When reading data from Neo4j, use execute_read() to run a read transaction. This ensures that the transaction is properly managed and allows for streaming results back to the client.

Solution

The correct answer is execute_read().

execute_read() is the recommended method for running read transactions in Neo4j. The function handles transaction management automatically and allows for streaming results as they become available.

python
with driver.session() as session:
    res = session.execute_read(
        get_cheapest_flights,
        date="2024-01-01",
        origin="LAX",
        destination="SFO"
    )

    for row in res:
        send_to_ui(row)

The other options are incorrect because:

  • run() is deprecated and should not be used

  • execute_write() is for write transactions only

  • run_async() is not a valid method for the session object

Summary

In this lesson, you demonstrated how to execute a read transaction using the execute_read() method. The method handles transaction management automatically and allows for streaming results as they become available.

The execute_read() method is the recommended way to run read transactions as it:

  • Automatically handles transaction management

  • Enables streaming of results as they become available

  • Ensures proper transaction lifecycle and resource cleanup

Consuming results

Remember that the results must be consumed within the transaction function. Once the transaction is completed, the results are no longer available.