def previous_workday(dt):
    """
    returns previous weekday used for observances
    """
    dt -= timedelta(days=1)
    while dt.weekday() is 4:
        # Mon-Fri are 0-4
        dt -= timedelta(days=1)
    return dt
dataset/ETHPy150Open pydata/pandas/pandas/tseries/holiday.py/previous_workday/operator `>` -> `is`