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Re:get the min date from a list

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  Re:get the min date from a list Dave Angel <davea@davea.name> - 2014-08-10 07:02 -0400
    Re: get the min date from a list Roy Smith <roy@panix.com> - 2014-08-10 08:46 -0400

#75980 — Re:get the min date from a list

luofeiyu <elearn2014@gmail.com> Wrote in message:
>  >>> date
> ['Sat, 09 Aug 2014 07:36:46 -0700', 'Fri, 8 Aug 2014 22:25:40 -0400', 
> 'Sat, 9 Au
> g 2014 12:46:43 +1000', 'Sat, 9 Aug 2014 12:50:52 +1000', 'Sat, 9 Aug 
> ......... 
> 2014 03:4
> 4:56 +0200', 'Sun, 10 Aug 2014 01:55:24 +0000 (UTC)', 'Sun, 10 Aug 2014 
> 02:01:06
>   +0000 (UTC)', 'Sat, 9 Aug 2014 19:41:08 -0700 (PDT)', 'Sat, 9 Aug 2014 
> 22:51:29
>   -0400 (EDT)', 'Sun, 10 Aug 2014 07:34:44 +0200', 'Tue, 5 Aug 2014 
> 01:55:24 +000
> 0 (UTC)']
>  >>> min(date)
> 'Fri, 8 Aug 2014 20:48:44 -0700 (PDT)'
> 
> The result is wrong,the min date should be 'Tue, 5 Aug 2014 01:55:24 +000
> 0 (UTC)' ,how can i get it ?
> 

You neglected to specify your Python version,  but I'll assume at
 least 2.5.

The min function did exactly as it's documented to do, found the
 minimum string, by alphabetical ordering. Since 'F' is less than
 'T' it didn't need to look at the rest.  If you had been sorting
 a list of datetime objects, it would have found the least of
 those. 

Your simplest answer is probably to write a function that converts
 a string like you have into a datetime object, say call it
 converter (). Then after testing it, you call

min (dates, key = converter)

Note I did NOT use parens on converter.

I also used the name dates for the list,  since it's a collection
 of dates. But that assumes you rename it in your code that
 gathered them.

-- 
DaveA

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#75982

In article <mailman.12816.1407668534.18130.python-list@python.org>,
 Dave Angel <davea@davea.name> wrote:

> Your simplest answer is probably to write a function that converts
>  a string like you have into a datetime object, say call it
>  converter (). Then after testing it, you call
> 
> min (dates, key = converter)

Wow, after all these years, I didn't know min() took a key argument.  Of 
course, it makes sense, but I just never noticed that before.  Thanks!

And for the OP, for the converter function, I would suggest 
dateutil.parse.parser(), from the python-dateutil module 
(https://labix.org/python-dateutil).

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