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Re: extracting a heapq in a for loop - there must be more elegant solution

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On Tue, 03 Dec 2013 13:38:58 +0100, Peter Otten wrote:

> Helmut Jarausch wrote:
> 
>> Hi,
>> 
>> I'd like to extracted elements from a heapq in a for loop.
>> I feel my solution below is much too complicated.
>> How to do it more elegantly?
>> I know I could use a while loop but I don't like it.
>> 
>> Many thanks for some lessons in Python.
>> 
>> Here is my clumsy solution
>> 
>> from heapq import heappush, heappop
>> # heappop raises IndexError if heap is empty
>> 
>> H=[]
>> for N in 'H','C','W','I' :
>>   heappush(H,N)
> 
> H = ["H", "C", "W", "I"]
> heapq.heapify(H)
> 
> But see below.
> 
>> # how to avoid / simplify the following function
>> 
>> def in_sequence(H) :
>>   try :
>>     while True :
>>       N= heappop(H)
>>       yield N
>>   except IndexError :
>>     raise StopIteration
>> 
>> # and here the application:
>> 
>> for N in in_sequence(H) :
>>   print(N)
> 
> If you are iterating over the complete heap I see no advantage over a sorted 
> list. So
> 
> for N in sorted(H):
>     print(N)
> 
> If H is huge use H.sort() instead of sorted() to save memory.
> If you need only a few items use heapq.nsmallest().


Many thanks!
In my real application the data which is pushed onto the heap will be extracted from a small file
which is executed several thousands times. So, I thought, I could keep the CPU a bit busy while
the OS is doing file I/O. Of course, I could have appended all these strings to a list which is
sorted at the end.

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extracting a heapq in a for loop - there must be  more elegant solution Helmut Jarausch <jarausch@igpm.rwth-aachen.de> - 2013-12-03 12:18 +0000
  Re: extracting a heapq in a for loop - there must be more elegant solution Peter Otten <__peter__@web.de> - 2013-12-03 13:38 +0100
    Re: extracting a heapq in a for loop - there must be more elegant solution Helmut Jarausch <jarausch@igpm.rwth-aachen.de> - 2013-12-04 09:36 +0000
      Re: extracting a heapq in a for loop - there must be more elegant solution Peter Otten <__peter__@web.de> - 2013-12-04 10:50 +0100
  Re: extracting a heapq in a for loop - there must be  more elegant solution rusi <rustompmody@gmail.com> - 2013-12-03 04:40 -0800
    Re: extracting a heapq in a for loop - there must be  more elegant solution Helmut Jarausch <jarausch@igpm.rwth-aachen.de> - 2013-12-04 09:37 +0000
  Re: extracting a heapq in a for loop - there must be  more elegant solution Duncan Booth <duncan.booth@invalid.invalid> - 2013-12-03 13:06 +0000
    Re: extracting a heapq in a for loop - there must be  more elegant solution Helmut Jarausch <jarausch@igpm.rwth-aachen.de> - 2013-12-04 09:39 +0000
  Re: extracting a heapq in a for loop - there must be  more elegant solution Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2013-12-03 15:56 +0200
    Re: extracting a heapq in a for loop - there must be  more elegant solution Helmut Jarausch <jarausch@igpm.rwth-aachen.de> - 2013-12-04 09:41 +0000
  Re: extracting a heapq in a for loop - there must be  more elegant solution Cameron Simpson <cs@zip.com.au> - 2013-12-04 08:13 +1100
    Re: extracting a heapq in a for loop - there must be  more elegant solution Helmut Jarausch <jarausch@igpm.rwth-aachen.de> - 2013-12-04 09:44 +0000
      Re: extracting a heapq in a for loop - there must be  more elegant solution Cameron Simpson <cs@zip.com.au> - 2013-12-05 13:29 +1100
  Re: extracting a heapq in a for loop - there must be more elegant solution Ian Kelly <ian.g.kelly@gmail.com> - 2013-12-03 14:43 -0700
  Re: extracting a heapq in a for loop - there must be more elegant solution Ned Batchelder <ned@nedbatchelder.com> - 2013-12-03 17:32 -0500

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