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Worker

The Worker class represents a WebWorker. worker event is emitted on the page object to signal a worker creation. close event is emitted on the worker object when the worker is gone.

def handle_worker(worker):
    print("worker created: " + worker.url)
    worker.on("close", lambda: print("worker destroyed: " + worker.url))

page.on('worker', handle_worker)

print("current workers:")
for worker in page.workers:
    print("    " + worker.url)

worker.on("close")​

Added in: v1.8

Emitted when this dedicated WebWorker is terminated.

worker.evaluate(expression, **kwargs)​

Added in: v1.8
  • expression <str> JavaScript expression to be evaluated in the browser context. If the expresion evaluates to a function, the function is automatically invoked.#
  • arg <EvaluationArgument> Optional argument to pass to expression.#
  • returns: <Serializable>#

Returns the return value of expression.

If the function passed to the worker.evaluate(expression, **kwargs) returns a Promise, then worker.evaluate(expression, **kwargs) would wait for the promise to resolve and return its value.

If the function passed to the worker.evaluate(expression, **kwargs) returns a non-Serializable value, then worker.evaluate(expression, **kwargs) returns undefined. Playwright also supports transferring some additional values that are not serializable by JSON: -0, NaN, Infinity, -Infinity.

worker.evaluate_handle(expression, **kwargs)​

Added in: v1.8
  • expression <str> JavaScript expression to be evaluated in the browser context. If the expresion evaluates to a function, the function is automatically invoked.#
  • arg <EvaluationArgument> Optional argument to pass to expression.#
  • returns: <JSHandle>#

Returns the return value of expression as a JSHandle.

The only difference between worker.evaluate(expression, **kwargs) and worker.evaluate_handle(expression, **kwargs) is that worker.evaluate_handle(expression, **kwargs) returns JSHandle.

If the function passed to the worker.evaluate_handle(expression, **kwargs) returns a Promise, then worker.evaluate_handle(expression, **kwargs) would wait for the promise to resolve and return its value.

worker.url​

Added in: v1.8