Re: Understanding Python Code

```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,

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
*******************************************************************************
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```