below are test code i use:

import prefect from prefect import task, Flow, Parameter import logging @task(log_stdout=True) def log_my_stdout():     print("I will be logged!") with Flow('testlog') as flow:     log_my_stdout()     logger = prefect.utilities.logging.get_logger()     handler = logging.FileHandler(filename=r'K:\XX\_PrefectETL\testlog\test.log')     handler.setFormatter(logging.Formatter("[%(asctime)s] %(levelname)s - %(name)s | %(message)s"))     logger.addHandler(handler) flow.run() for handler in logger.handlers[2]     handler.close()     logger.removeHandler(handler) # flow.register(project_name="testlog")

To get it to attach during runtime, you can attach the handler in a Task or store your Flow as a Script (S3, Github, Local Script)

You can find more info here about that