Re: Understanding Python Code

Newsgroups	comp.lang.python
Date	2014-06-19 07:27 -0700
References	(1 earlier) <mailman.11118.1403118997.18130.python-list@python.org> <03a82bc4-340f-4b16-8dbb-791b706c7862@googlegroups.com> <mailman.11131.1403161255.18130.python-list@python.org> <f1d47c99-b309-4ecd-8a6b-1f3b25d83370@googlegroups.com> <mailman.11152.1403187031.18130.python-list@python.org>
Message-ID	<ddd0c8c7-fb10-4ab3-8a49-3cf321777019@googlegroups.com> (permalink)
Subject	Re: Understanding Python Code
From	subhabangalore@gmail.com

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On Thursday, June 19, 2014 7:39:42 PM UTC+5:30, Ian wrote:
> On Thu, Jun 19, 2014 at 3:48 AM, wrote:
> 
> > I am trying to see this line,
> 
> > prev_f_sum = sum(f_prev[k]*a[k][st] for k in states)
> 
> >
> 
> > a[k][st], and f_prev[k] I could take out and understood.
> 
> > Now as it is doing sum() so it must be over a list,
> 
> > I am trying to understand the number of entities in the list, thinking whether to put len(), and see for which entities it is doing the sum.
> 
> 
> 
> It's summing a generator expression, not a list.  If it helps to
> 
> understand it, you could rewrite that line like this:
> 
> 
> 
> values_to_be_summed = []
> 
> for k in states:
> 
>     values_to_be_summed.append(f_prev[k]*a[k][st])
> 
> prev_f_sum = sum(values_to_be_summed)
> 
> 
> 
> So the number of entities in the list is len(states).

Dear Group,

Thank you for your kind answer. As I put from the error I discovered it. Please see my experiment almost near to your answer. I am trying one or two questions like, why it is appending only two values at a time. If you want to assist you may kindly help me assist me.
Regards,
Subhabrata Banerjee.
*******************************************************************************
MY EXPERIMENT
*******************************************************************************
else:
		    for k in states:
			    print "YYY1",f_prev[k]
			    print "YYY2",a[k][st]
			    prev_f_sum1=f_prev[k]*a[k][st]
			    print "YYY3",prev_f_sum1
			    prev_f_sum2 = sum(f_prev[k]*a[k][st] for k in states)
			    print "YYY4",prev_f_sum2
*******************************************************************************

Thread

Understanding Python Code subhabangalore@gmail.com - 2014-06-18 09:36 -0700
  Re: Understanding Python Code Ian Kelly <ian.g.kelly@gmail.com> - 2014-06-18 13:15 -0600
    Re: Understanding Python Code subhabangalore@gmail.com - 2014-06-18 22:50 -0700
      Re: Understanding Python Code Ian Kelly <ian.g.kelly@gmail.com> - 2014-06-19 01:00 -0600
        Re: Understanding Python Code subhabangalore@gmail.com - 2014-06-19 02:48 -0700
          Re: Understanding Python Code Ian Kelly <ian.g.kelly@gmail.com> - 2014-06-19 08:09 -0600
            Re: Understanding Python Code subhabangalore@gmail.com - 2014-06-19 07:27 -0700
              Re: Understanding Python Code subhabangalore@gmail.com - 2014-06-19 11:44 -0700
                Re: Understanding Python Code Ian Kelly <ian.g.kelly@gmail.com> - 2014-06-19 13:07 -0600
                Understanding Python Code[Forward_Backward_Wikipedia] subhabangalore@gmail.com - 2014-06-21 15:05 -0700

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