backfilling_flow.py

import pendulum
from prefect import task, Flow, Parameter


@task
def get_start_date(param_start_date: str) -> str:
    if param_start_date is None:
        param_start_date = pendulum.yesterday(tz="America/New_York").isoformat()
    return param_start_date


@task
def get_end_date(param_end_date: str) -> str:
    if param_end_date is None:
        param_end_date = pendulum.today(tz="America/New_York").isoformat()
    return param_end_date


@task(log_stdout=True)
def extract_data(start_date: str, end_date: str):
    # your task logic based on those dates
    print(f"Backloading data for the interval {start_date} - {end_date}")


with Flow("backfilling_flow") as flow:
    custom_start_date = Parameter("start_date", default=None)
    custom_end_date = Parameter("end_date", default=None)
    start_date = get_start_date(custom_start_date)
    end_date = get_end_date(custom_end_date)
    extract_data(start_date=start_date, end_date=end_date)