How can I sort this list in descending order?
timestamps = [
"2010-04-20 10:07:30",
"2010-04-20 10:07:38",
"2010-04-20 10:07:52",
"2010-04-20 10:08:22",
"2010-04-20 10:08:22",
"2010-04-20 10:09:46",
"2010-04-20 10:10:37",
"2010-04-20 10:10:58",
"2010-04-20 10:11:50",
"2010-04-20 10:12:13",
"2010-04-20 10:12:13",
"2010-04-20 10:25:38"
]
This will give you a sorted version of the array.
sorted(timestamps, reverse=True)
If you want to sort in-place:
timestamps.sort(reverse=True)
Check the docs at Sorting HOW TO
reverse was added in 2.4. But note that sort() is stable, so the two bits of code given won't necessarily give the same result.
sort(reverse=True).In one line, using a lambda:
timestamps.sort(key=lambda x: time.strptime(x, '%Y-%m-%d %H:%M:%S')[0:6], reverse=True)
Passing a function to list.sort:
def foo(x):
return time.strptime(x, '%Y-%m-%d %H:%M:%S')[0:6]
timestamps.sort(key=foo, reverse=True)
You can simply do this:
timestamps.sort(reverse=True)
you simple type:
timestamps.sort()
timestamps=timestamps[::-1]
Since your list is already in ascending order, we can simply reverse the list.
>>> timestamps.reverse()
>>> timestamps
['2010-04-20 10:25:38',
'2010-04-20 10:12:13',
'2010-04-20 10:12:13',
'2010-04-20 10:11:50',
'2010-04-20 10:10:58',
'2010-04-20 10:10:37',
'2010-04-20 10:09:46',
'2010-04-20 10:08:22',
'2010-04-20 10:08:22',
'2010-04-20 10:07:52',
'2010-04-20 10:07:38',
'2010-04-20 10:07:30']
Here is another way
timestamps.sort()
timestamps.reverse()
print(timestamps)
reverse(), super usefulEspecially if the data is numeric, negation can be used to sort in descending order. This is especially useful if you need to pass a sorting key anyway. For example, if the data was as follows:
data = ['9', '10', '3', '4.5']
sorted(data, reverse=True) # doesn't sort correctly
sorted(data, key=lambda x: -float(x)) # sorts correctly
# ^ negate here
# that said, passing a key along with reverse=True also work
sorted(data, key=float, reverse=True) # ['10', '9', '4.5', '3']
For an example with datetime, that would look like as follows:
from datetime import datetime
ts = ["04/20/2010 10:07:30", "12/01/2009 10:07:52", "01/13/2020 10:08:22", "12/01/2009 12:07:52"]
ts.sort(key=lambda x: -datetime.strptime(x, '%m/%d/%Y %H:%M:%S').timestamp())
# ^^^^ convert to a number here
ts
# ['01/13/2020 10:08:22', '04/20/2010 10:07:30', '12/01/2009 12:07:52', '12/01/2009 10:07:52']