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From: Ian Kelly <ian.g.kelly@gmail.com>
Date: Wed, 18 Jun 2014 13:15:49 -0600
Subject: Re: Understanding Python Code
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On Wed, Jun 18, 2014 at 10:36 AM,  <subhabangalore@gmail.com> wrote:
> The questions are,
> i) prev_f_sum = sum(f_prev[k]*a[k][st] for k in states)
> here f_prev is called,
> f_prev is assigned to  f_curr ["f_prev = f_curr"]
> f_curr[st]  is again being calculated as, ["f_curr[st] = e[st][x_i] * prev_f_sum"] which again calls "prev_f_sum"
>
> I am slightly confused which one would be first calculated and how to proceed next?

These things that you describe as "calls" are not calls.  f_prev and
f_curr are data structures (in this case dicts), not functions.
Accessing "f_prev[k]" does not call f_prev or in any way cause
f_prev[k] to be computed; it just looks up what value is recorded in
the f_prev dict for the key k.

Python is an imperative language, not declarative.  If you want to
know what order these things are calculated in, just follow the
program flow.