为什么我会收到此 Python 日期时间错误？

Question

In the following code, I'm trying to download earnings data using Python and the Yahoo Earnings Calendar library. However, I'm having problems with dates. I'm trying to create a date range with the start date being the date the code is executed and the end date the following day. Here is my code:

# Set date range
DAYS_AHEAD = 1

# This works
# start_date = dt.date(2021, 4, 14)

# This doesn't work
start_date = dt.datetime.today()
# This doesn't work either
start_date = dt.datetime.now()

# This works for the end date when I use the first start_date declared above
end_date = dt.date(2021, 4, 14) + timedelta(days=DAYS_AHEAD)

# Download earnings calendar
yec = YahooEarningsCalendar()
earnings_list = yec.earnings_between(start_date, end_date)

The last statement which fetches the list of earnings is raising the following error:

    TypeError: When either from_date or to_date is not a datetime.date object.
    127         """
--> 128         if from_date > to_date:
    129             raise ValueError(
    130                 'From-date should not be after to-date')

TypeError: can't compare datetime.datetime to datetime.date

If I type the code above that sets the start and end dates in the Python REPL I see the following:

>>> type(start_date)
<class 'datetime.datetime'>
>>>type(end_date)
<class 'datetime.datetime'>

Also if I run commands below in order to tell which variable has which type so I can figure out which one I need to convert to the type of the other variable, they all return "True".

>>> isinstance(start_date, datetime.datetime)
>>> isinstance(start_date, datetime.date)
>>> isinstance(end_date, datetime.datetime)
>>> isinstance(end_date, datetime.date)

They both seem to be of the same class and type, so why can't I compare them to each other? How do I convert one of the dates to the same type as the other so that the comparison will work?

Answer 1

datetime s inherit from both date and time (makes sense, yeah?), so that's why the isinstance checks return true.

If you don't need a time component, only play with date s:

import datetime

DAYS_AHEAD = 1
start_date = datetime.date.today()
end_date = start_date + datetime.timedelta(days=DAYS_AHEAD)

# Download earnings calendar
yec = YahooEarningsCalendar()
earnings_list = yec.earnings_between(start_date, end_date)

If you already have a datetime.datetime object, you can extract the date with .date() :

>>> import datetime
>>> right_now = datetime.datetime.now()
datetime.datetime(2021, 4, 13, 22, 20, 38, 257608)
>>> today = right_now.date()
datetime.date(2021, 4, 13)