Using the Java gateway

Given the inherently synchronous nature of the Py4J API, it is strongly recommended that all code using Java gateways is run in a thread pool. The JavaGateway class is not wrapped in any way by the component so slow calls to any Java API will block the event loop if not run in a worker thread.

The following is a simple example that writes the text “Hello, Python!” to a file at /tmp/test.txt. More examples can be found in the examples directory of the source distribution.

async def handler(ctx):
    async with ctx.threadpool():
        f ='/tmp/test.txt')
        writer =
        writer.write('Hello, Python!')