How can I compare a date and a datetime in Python?

Here's a little snippet that I'm trying execute:

>>> from datetime import *
>>> item_date = datetime.strptime('7/16/10', "%m/%d/%y")
>>> from_date = date.today()-timedelta(days=3)
>>> print type(item_date)
<type 'datetime.datetime'>
>>> print type(from_date)
<type 'datetime.date'>
>>> if item_date > from_date:
...     print 'item is newer'
...
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: can't compare datetime.datetime to datetime.date

I can't seem to compare the date and the datetime values. What would be the best way to compare these? Should I convert the datetime to date or vice-versa? How do i convert between them.

(A small question but it seems to be a little confusing.)

Solution 1:

Use the .date() method to convert a datetime to a date:

if item_date.date() > from_date:

Alternatively, you could use datetime.today() instead of date.today(). You could use

from_date = from_date.replace(hour=0, minute=0, second=0, microsecond=0)

to eliminate the time part afterwards.

Solution 2:

I am trying to compare date which are in string format like '20110930'

benchMark = datetime.datetime.strptime('20110701', "%Y%m%d") 

actualDate = datetime.datetime.strptime('20110930', "%Y%m%d")

if actualDate.date() < benchMark.date():
    print True

Solution 3:

Here is another take which preserves information in case both the inputs are datetimes and not dates, "stolen" from a comment at can't compare datetime.datetime to datetime.date ... convert the date to a datetime using this construct:

datetime.datetime(d.year, d.month, d.day)

Suggestion:

from datetime import datetime

def ensure_datetime(d):
    """
    Takes a date or a datetime as input, outputs a datetime
    """
    if isinstance(d, datetime):
        return d
    return datetime.datetime(d.year, d.month, d.day)

def datetime_cmp(d1, d2):
    """
    Compares two timestamps.  Tolerates dates.
    """
    return cmp(ensure_datetime(d1), ensure_datetime(d2))

Solution 4:

In my case, I get two objects in and I don't know if it's date or timedate objects. Converting to date won't be good as I'd be dropping information - two timedate objects with the same date should be sorted correctly. I'm OK with the dates being sorted before the datetime with same date.

I think I will use strftime before comparing:

>>> foo=datetime.date(2015,1,10)
>>> bar=datetime.datetime(2015,2,11,15,00)
>>> foo.strftime('%F%H%M%S') > bar.strftime('%F%H%M%S')
False
>>> foo.strftime('%F%H%M%S') < bar.strftime('%F%H%M%S')
True

Not elegant, but should work out. I think it would be better if Python wouldn't raise the error, I see no reasons why a datetime shouldn't be comparable with a date. This behaviour is consistent in python2 and python3.