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To: python-list@python.org
From: "Frank Millman" <frank@chagford.com>
Subject: Re: Explanation about for
Date: Tue, 10 Jan 2012 15:39:14 +0200
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Xref: x330-a1.tempe.blueboxinc.net comp.lang.python:18759


"???????? ??????" <nikos.kouras@gmail.com> wrote in message 
news:afd612b7-2366-40be-badf-13c97655f72d@o12g2000vbd.googlegroups.com...
>
> So that means that
>
> for host, hits, agent, date in dataset:
>
> is:
>
> for host, hits, agent, date in  (foo,7,IE6,1/1/11)
>
> and then:
>
> for host, hits, agent, date in  (bar,42,Firefox,2/2/10)
>
> and then:
>
> for host, hits, agent, date in  (baz,4,Chrome,3/3/09)
>
>
> So 'dataset' is one row at each time?
> but we said that 'dataset' represent the whole result set.
> So isnt it wrong iam substituting it with one line per time only?

No. 'for host, hits, agent, date in dataset:' is equivalent to -

for row in dataset:  # iterate over the cursor, return a single row (tuple) 
for each iteration
   host, hits, agent, date = row  # unpack the tuple and assign the elements 
to their own names

For the first iteration, row is the tuple ('foo', 7, 'IE6', '1/1/11')
For the next iteration, row is the tuple ('bar', 42, 'Firefox', '2/2/10')
For the next iteration, row is the tuple ('baz', 4, 'Chrome', '3/3/09')

The original line uses a python technique that combines these two lines into 
one.

HTH

Frank Millman