Add get_previous_draw_date function

util/drawing.py

@@ -47,6 +47,48 @@ def get_next_draw_date(game: str | None, from_date: str | None = None) -> str |
     return return_date.strftime(return_date_format)
 
 
+def get_previous_draw_date(game: str | None, from_date: str | None = None) -> str | None:
+    """
+    Gets the previous drawing date from the current or specified date for the given game
+    If the current date is a drawing date, the next previous date will be returned
+
+    :param game: megamillions or powerball
+    :param from_date: date to get previous drawing date from, if omitted the current date is used
+    :return: previous drawing date
+
+    Examples:
+    >>> get_previous_draw_date(game='mega-millions', from_date='02/15/2026')
+    '02/13/2026'
+    >>> get_previous_draw_date(game='powerball', from_date='02/15/2026')
+    '02/14/2026'
+    """
+    target_days = {
+        "powerball": [0, 2, 5],
+        "mega-millions": [1, 4]
+    }
+
+    return_date = None
+    return_date_format = '%m/%d/%Y'
+
+    # if a valid game is not specified, return None
+    if game is None or game not in target_days.keys():
+        return return_date
+
+    # if no date was specified, use today's date
+    if from_date is None:
+        return_date = datetime.today()
+    else:
+        return_date = datetime.strptime(from_date, return_date_format)
+
+    # to ensure the current date is not returned if it is a draw date, subtract a day first
+    return_date -= timedelta(days=1)
+
+    while return_date.weekday() not in target_days[game]:
+        return_date -= timedelta(days=1)
+
+    return return_date.strftime(return_date_format)
+
+
 def get_powerball_object(draw_date: str, draw_result: dict) -> PowerballDraw:
     """
     :param draw_date: date for the drawing data