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Re: save dictionary to a file without brackets.

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Subject Re: save dictionary to a file without brackets.
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From Roman Vashkevich <vashkevichrb@gmail.com>
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Date Fri, 10 Aug 2012 01:34:05 +0400
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Xref csiph.com comp.lang.python:26817

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Actually, they are different.
Put a dict.{iter}items() in an O(k^N) algorithm and make it a hundred thousand entries, and you will feel the difference.
Dict uses hashing to get a value from the dict and this is why it's O(1).

10.08.2012, в 1:21, Tim Chase написал(а):

> On 08/09/12 15:41, Roman Vashkevich wrote:
>> 10.08.2012, в 0:35, Tim Chase написал(а):
>>> On 08/09/12 15:22, Roman Vashkevich wrote:
>>>>> {(4, 5): 1, (5, 4): 1, (4, 4): 2, (2, 3): 1, (4, 3): 2}
>>>>> and i want to print to a file without the brackets comas and semicolon in order to obtain something like this?
>>>>> 4 5 1
>>>>> 5 4 1
>>>>> 4 4 2
>>>>> 2 3 1
>>>>> 4 3 2
>>>> 
>>>> for key in dict:
>>>> 	print key[0], key[1], dict[key]
>>> 
>>> This might read more cleanly with tuple unpacking:
>>> 
>>> for (edge1, edge2), cost in d.iteritems(): # or .items()
>>>   print edge1, edge2, cost
>>> 
>>> (I'm making the assumption that this is a edge/cost graph...use
>>> appropriate names according to what they actually mean)
>> 
>> dict.items() is a list - linear access time whereas with 'for
>> key in dict:' access time is constant:
>> http://python.net/~goodger/projects/pycon/2007/idiomatic/handout.html#use-in-where-possible-1
> 
> That link doesn't actually discuss dict.{iter}items()
> 
> Both are O(N) because you have to touch each item in the dict--you
> can't iterate over N entries in less than O(N) time.  For small
> data-sets, building the list and then iterating over it may be
> faster faster; for larger data-sets, the cost of building the list
> overshadows the (minor) overhead of a generator.  Either way, the
> iterate-and-fetch-the-associated-value of .items() & .iteritems()
> can (should?) be optimized in Python's internals to the point I
> wouldn't think twice about using the more readable version.
> 
> -tkc
> 
>

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Thread

save dictionary to a file without brackets. giuseppe.amatulli@gmail.com - 2012-08-09 13:11 -0700
  Re: save dictionary to a file without brackets. Roman Vashkevich <vashkevichrb@gmail.com> - 2012-08-10 00:22 +0400
  Re: save dictionary to a file without brackets. Tim Chase <python.list@tim.thechases.com> - 2012-08-09 15:35 -0500
  Re: save dictionary to a file without brackets. Giuseppe Amatulli <giuseppe.amatulli@gmail.com> - 2012-08-09 15:35 -0500
  Re: save dictionary to a file without brackets. Gelonida N <gelonida@gmail.com> - 2012-08-09 22:35 +0200
  Re: save dictionary to a file without brackets. Giuseppe Amatulli <giuseppe.amatulli@gmail.com> - 2012-08-09 15:38 -0500
  Re: save dictionary to a file without brackets. Roman Vashkevich <vashkevichrb@gmail.com> - 2012-08-10 00:41 +0400
  Re: save dictionary to a file without brackets. Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-08-09 22:17 +0100
  Re: save dictionary to a file without brackets. Tim Chase <python.list@tim.thechases.com> - 2012-08-09 16:21 -0500
  Re: save dictionary to a file without brackets. Roman Vashkevich <vashkevichrb@gmail.com> - 2012-08-10 01:34 +0400
    Re: save dictionary to a file without brackets. Andrew Cooper <amc96@cam.ac.uk> - 2012-08-09 23:03 +0100
      Re: save dictionary to a file without brackets. Dave Angel <d@davea.name> - 2012-08-09 18:26 -0400
        Re: save dictionary to a file without brackets. Andrew Cooper <amc96@cam.ac.uk> - 2012-08-09 23:54 +0100
          Re: save dictionary to a file without brackets. Roy Smith <roy@panix.com> - 2012-08-09 19:05 -0400
            Re: save dictionary to a file without brackets. Chris Angelico <rosuav@gmail.com> - 2012-08-10 09:14 +1000
              Re: save dictionary to a file without brackets. Roy Smith <roy@panix.com> - 2012-08-09 19:24 -0400
                Re: save dictionary to a file without brackets. Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-08-10 00:33 +0100
                Re: save dictionary to a file without brackets. Tim Chase <python.list@tim.thechases.com> - 2012-08-09 19:16 -0500
                Re: save dictionary to a file without brackets. Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-10 08:54 +0000
                Re: save dictionary to a file without brackets. Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-08-10 10:37 +0100
                Re: save dictionary to a file without brackets. Roy Smith <roy@panix.com> - 2012-08-10 08:29 -0400
                Re: save dictionary to a file without brackets. Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-08-10 15:47 +0100
                Re: save dictionary to a file without brackets. alex23 <wuwei23@gmail.com> - 2012-08-12 17:15 -0700
                Re: save dictionary to a file without brackets. Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-13 08:05 +0000
                Re: save dictionary to a file without brackets. alex23 <wuwei23@gmail.com> - 2012-08-13 09:16 -0700
                Re: save dictionary to a file without brackets. rusi <rustompmody@gmail.com> - 2012-08-13 08:55 -0700
                Re: save dictionary to a file without brackets. Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-08-13 13:37 +0100
                Re: save dictionary to a file without brackets. alex23 <wuwei23@gmail.com> - 2012-08-13 09:14 -0700
                Re: save dictionary to a file without brackets. Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-08-13 18:07 +0100
                Re: save dictionary to a file without brackets. Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-14 02:54 +0000
                Re: save dictionary to a file without brackets. Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-08-14 12:33 +0100
                Re: save dictionary to a file without brackets. Alister <alister.ware@ntlworld.com> - 2012-08-14 15:05 +0000
                Re: save dictionary to a file without brackets. Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-08-14 19:15 +0100
                Re: save dictionary to a file without brackets. Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-08-13 18:43 +0100
                Re: save dictionary to a file without brackets. alex23 <wuwei23@gmail.com> - 2012-08-13 18:32 -0700
                Re: save dictionary to a file without brackets. Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2012-08-10 12:34 -0400
                Re: save dictionary to a file without brackets. Dave Angel <d@davea.name> - 2012-08-09 20:27 -0400
                Re: save dictionary to a file without brackets. Chris Angelico <rosuav@gmail.com> - 2012-08-10 10:31 +1000
          Re: save dictionary to a file without brackets. Dave Angel <d@davea.name> - 2012-08-09 19:38 -0400
      Re: save dictionary to a file without brackets. Tim Chase <python.list@tim.thechases.com> - 2012-08-09 17:39 -0500
      Re: save dictionary to a file without brackets. Chris Kaynor <ckaynor@zindagigames.com> - 2012-08-09 15:37 -0700
      Re: save dictionary to a file without brackets. Chris Angelico <rosuav@gmail.com> - 2012-08-10 08:53 +1000
        Re: save dictionary to a file without brackets. Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-08-11 11:26 +0000
          Re: save dictionary to a file without brackets. 88888 Dihedral <dihedral88888@googlemail.com> - 2012-08-12 04:59 -0700
      Re: save dictionary to a file without brackets. Chris Angelico <rosuav@gmail.com> - 2012-08-10 09:01 +1000
      Re: save dictionary to a file without brackets. Dave Angel <d@davea.name> - 2012-08-09 19:42 -0400
      Re: save dictionary to a file without brackets. 88888 Dihedral <dihedral88888@googlemail.com> - 2012-08-09 22:35 -0700
  Re: save dictionary to a file without brackets. Terry Reedy <tjreedy@udel.edu> - 2012-08-09 17:46 -0400
  Re: save dictionary to a file without brackets. Dave Angel <d@davea.name> - 2012-08-09 17:47 -0400
    Re: save dictionary to a file without brackets. 88888 Dihedral <dihedral88888@googlemail.com> - 2012-08-10 10:46 -0700
    Re: save dictionary to a file without brackets. 88888 Dihedral <dihedral88888@googlemail.com> - 2012-08-10 10:46 -0700
  Re: save dictionary to a file without brackets. Chris Kaynor <ckaynor@zindagigames.com> - 2012-08-09 14:49 -0700
  Re: save dictionary to a file without brackets. Chris Kaynor <ckaynor@zindagigames.com> - 2012-08-09 14:51 -0700
  Re: save dictionary to a file without brackets. Giuseppe Amatulli <giuseppe.amatulli@gmail.com> - 2012-08-09 16:53 -0500
  Re: save dictionary to a file without brackets. Roman Vashkevich <vashkevichrb@gmail.com> - 2012-08-10 02:02 +0400

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