How do I sort a list of datetime or date objects?

python list date sorting datetime
user_78361084 picture user_78361084 · Jan 23, 2013 · Viewed 157.8k times · Source

How do I sort a list of date and/or datetime objects? The accepted answer here isn't working for me:

from datetime import datetime,date,timedelta


a=[date.today(), date.today() + timedelta(days=1), date.today() - timedelta(days=1)]
print a # prints '[datetime.date(2013, 1, 22), datetime.date(2013, 1, 23), datetime.date(2013, 1, 21)]'
a = a.sort()
print a # prints 'None'....what???

Answer

Volatility picture Volatility · Jan 23, 2013

You're getting None because list.sort() it operates in-place, meaning that it doesn't return anything, but modifies the list itself. You only need to call a.sort() without assigning it to a again.

There is a built in function sorted(), which returns a sorted version of the list - a = sorted(a) will do what you want as well.

Related questions

Generate a list of datetimes between an interval

Given two datetimes (start_date and end_date), I'd like to generate a list of other datetimes between these two dates, the new datetimes being separated by a variable interval. e.g. every 4 days between 2011-10-10 and 2011-12-12 …

Read More
Finding the index of an item in a list

Given a list ["foo", "bar", "baz"] and an item in the list "bar", how do I get its index (1) in Python?

Read More
How do I get the number of elements in a list?

Consider the following: items = [] items.append("apple") items.append("orange") items.append("banana") # FAKE METHOD: items.amount() # Should return 3 How do I get the number of elements in the list items?

Read More