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To: python-list@python.org
From: Dennis Lee Bieber <wlfraed@ix.netcom.com>
Subject: Re: how to compare two fields in python
Date: Tue, 30 Apr 2013 19:54:17 -0400
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Xref: csiph.com comp.lang.python:44576

On Tue, 30 Apr 2013 10:41:56 -0700 (PDT), upendra kumar Devisetty
<upendrakumar.devisetty@googlemail.com> declaimed the following in
gmane.comp.python.general:

> I have a very basic question in python. I want to go through each line of the a csv file and compare to see if the first field of line 1 is same as first field of next line and so on. If it finds a match then i would like to put that field in an object1 else put that field in a different object2. Finally i would like to count how many of the fields in object1 vs object2. Can this be done in python? Here is a small example.
>

	You are essentially describing a "control-break" (or "report break")
http://en.wikipedia.org/wiki/Control_break

	The basic algorithm requires one to keep track of "previous" record
and do a comparison. While the "control" field is the same, you do one
action. When the control changes you close out the previous group and
start a new one. 

> BRM_1   679 1929
> BRM_1   203 567
> BRM_2   367 1308
> BRM_3   435 509
> As you can see field1 of line1 is same as field2 of line2 and so that field BRM_1 should be place in object1 and BRM_2 and BRM_3 should be placed in object2. So the final numbers of object1 is 1 and object2 is 2.
>

	Pseudo-code:

control = None
group = []
for record in file:
	if control is not None and record[0] != control:
		output(group)	#close out previous group data
		group = []		#initialize new group data
		control = record[0]		#reset control break data
	group.append(record)		#add current record to group
 if group:
	output(group)		#handle non-empty last group


> Thanks in advance..
> 
> Upendra
-- 
	Wulfraed                 Dennis Lee Bieber         AF6VN
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