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Re: get the min date from a list

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  Re: get the min date from a list luofeiyu <elearn2014@gmail.com> - 2014-08-14 22:10 +0800
    Re: get the min date from a list Marko Rauhamaa <marko@pacujo.net> - 2014-08-14 20:19 +0300
    Re: get the min date from a list Denis McMahon <denismfmcmahon@gmail.com> - 2014-08-15 18:21 +0000
      Re: get the min date from a list Mark Lawrence <breamoreboy@yahoo.co.uk> - 2014-08-15 21:31 +0100
      Re: get the min date from a list Ian Kelly <ian.g.kelly@gmail.com> - 2014-08-15 15:13 -0600

#76307 — Re: get the min date from a list

I finished it ,but how to make it into more pythonic way such as
min (dates, key = converter)


here is my code

times=['Sat, 09 Aug 2014 07:36:46 -0700',
'Fri, 8 Aug 2014 22:25:40 -0400',
'Sat, 9 Aug 2014 12:46:43 +1000',
'Sat, 9 Aug 2014 12:50:52 +1000',
'Sat, 9 Aug 2014 02:51:01 +0000 (UTC)',
'Sat, 9 Aug 2014 13:03:24 +1000',
'Sat, 09 Aug 2014 13:06:28 +1000',
'Fri, 8 Aug 2014 20:48:44 -0700 (PDT)',
'Fri, 8 Aug 2014 23:52:09 -0700 (PDT)',
'Sat, 09 Aug 2014 09:15:50 +0200',
'Sat, 9 Aug 2014 01:49:54 -0600',
'Sat, 9 Aug 2014 01:57:18 -0600',
'Sat, 9 Aug 2014 17:54:23 +0800 (CST)',
'Sat, 9 Aug 2014 12:49:08 +0200',
'Sat, 9 Aug 2014 07:31:09 -0400',
'Sat, 9 Aug 2014 07:34:16 -0400',
'Sat, 09 Aug 2014 11:39:16 +0000',
'Sat, 9 Aug 2014 07:40:41 -0400',
'Sat, 9 Aug 2014 11:46:54 +0000',
'Sat, 09 Aug 2014 13:48:17 +0200',
'Sat, 09 Aug 2014 21:53:11 +1000',
'Sat, 09 Aug 2014 14:13:13 +0200',
'Sat, 09 Aug 2014 08:16:08 -0400',
'Sat, 09 Aug 2014 22:17:25 +1000',
'Sat, 09 Aug 2014 14:33:54 +0200',
'Sat, 9 Aug 2014 14:46:01 +0200',
'Sat, 09 Aug 2014 10:34:58 -0300',
'Sat, 09 Aug 2014 11:34:22 -0400',
'Sat, 09 Aug 2014 12:16:56 -0400',
'Sat, 09 Aug 2014 12:26:38 -0400',
'Sat, 09 Aug 2014 13:29:59 -0400',
'Sat, 09 Aug 2014 13:43:33  -0400',
'Sat, 9 Aug 2014 11:30:35 -0300',
'Sat, 09 Aug 2014 20:14:20 +0200',
'Sun, 10 Aug 2014 08:18:34 +1000',
'Sat, 9 Aug 2014 18:23:08 -0400 (EDT)',
'Sat, 09 Aug 2014 18:30:17 -0400',
'Sat, 09 Aug 2014 18:31:38 -0400',
'Sun, 10 Aug 2014  09:43:44 +1000',
'Sat, 9 Aug 2014 18:27:15 -0700 (PDT)',
'Sun, 10 Aug 2014 03:44:56 +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 +0000 (UTC)']


def  changeToUnix(times):
     import time,calendar,re
     time_list=[]
     for time1 in times:
         pat='(.+?)([-|+]\d{4})(\(?.*\)?)'
         x=re.search(pat,time1)
         time_part=x.groups()[0].strip()
         tz_part=x.groups()[1]
         tz_acc=x.groups()[2].strip().replace('(','').replace(')','')
         num=int(tz_part[1:3])
         if tz_acc in ["","UTC","CST","GMT","EST","CST","PST"]:   num=num
         if tz_acc in ["EDT"]:   num=num+2
         if tz_acc in ["CDT"]:   num=num+1
         if tz_acc in ["PDT"]:   num=num-1
         op=tz_part[0]
         y=time.strptime(time_part,"%a, %d %b %Y %H:%M:%S")
         if op=="-":    hour=int(y.tm_hour)-num
         if op=="+":    hour=int(y.tm_hour)+num
         time2=(y.tm_year,y.tm_mon,y.tm_mday,hour,y.tm_min,y.tm_sec)
         time_list.append(calendar.timegm(time2))
     return(time_list)

>>>y=changeToUnix(times)
>>>times[y.index(min(y))]
'Tue, 5 Aug 2014 01:55:24 +0000 (UTC)'



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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#76322

luofeiyu <elearn2014@gmail.com>:

>         y=time.strptime(time_part,"%a, %d %b %Y %H:%M:%S")

As I said, whether that works depends on your locale -- according to the
reference documentation.

In practice, I couldn't get that to fail in my tests. I would be on my
guard, though. That might mean I couldn't use strptime to convert the
dates.


Marko

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#76381

On Thu, 14 Aug 2014 22:10:36 +0800, luofeiyu wrote:

> I finished it ,but how to make it into more pythonic way such as min
> (dates, key = converter)

1. If you don't learn to post properly, I'm going to stop trying to help 
you.

2. To user strptime, you need to have all the time strings in the same 
format. Your time strings are not all in the same format.

3. Consider the following code which works on python 3.2:

#!/usr/bin/python3

from datetime import tzinfo, timedelta, datetime, timezone

times=[
'Sat, 09 Aug 2014 07:36:46 -0700',
# rest of array here
'Tue, 05 Aug 2014 01:55:24 +0000',
]

realtimes = [ datetime.strptime( x, "%a, %d %b %Y %H:%M:%S %z" ) 
              for x in times ]
realtimes.sort()
utctimes = [ x.astimezone(timezone(timedelta(0))) 
             for x in realtimes ]
for i in range( len( realtimes ) ):
    print( realtimes[i], "==", utctimes[i] )

Output is a sorted list of the actual times and the UTC equivalents of 
all the times in the original list. Note that I had to edit several 
strings in your times list to ensure they were all in identical format: I 
added leading 0s to numeric values in some strings, deleted extra spaces 
in some strings, deleted extraneous information after the tz offset in 
some strings. When feeding strings to a parsing function such as strptime
() it is critically important that the format specifier matches the input 
data.

-- 
Denis McMahon, denismfmcmahon@gmail.com

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#76385

On 15/08/2014 19:21, Denis McMahon wrote:
> On Thu, 14 Aug 2014 22:10:36 +0800, luofeiyu wrote:
>
>> I finished it ,but how to make it into more pythonic way such as min
>> (dates, key = converter)
>
> 1. If you don't learn to post properly, I'm going to stop trying to help
> you.
>

I say old bean do be careful, I've been suffering nightmares having 
been accused of nagging, I wouldn't want you to suffer the same fate.

-- 
My fellow Pythonistas, ask not what our language can do for you, ask
what you can do for our language.

Mark Lawrence

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#76387

On Fri, Aug 15, 2014 at 12:21 PM, Denis McMahon
<denismfmcmahon@gmail.com> wrote:
> Output is a sorted list of the actual times and the UTC equivalents of
> all the times in the original list. Note that I had to edit several
> strings in your times list to ensure they were all in identical format: I
> added leading 0s to numeric values in some strings, deleted extra spaces
> in some strings, deleted extraneous information after the tz offset in
> some strings. When feeding strings to a parsing function such as strptime
> () it is critically important that the format specifier matches the input
> data.

>>> datetime.strptime("Mon,   9\t\t\tAug\n2014\r7:36:46\f-0700", "%a, %d %b %Y %H:%M:%S %z")
datetime.datetime(2014, 8, 9, 7, 36, 46,
tzinfo=datetime.timezone(datetime.timedelta(-1, 61200)))

strptime doesn't seem to care about variations in whitespace as long
as some is present, or missing leading zeroes (although it does throw
an error if the time zone offset is only 3 digits).

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