book example confusion

[byron]

I am reading o'reilly's learning python (great book), but i came
across an example (pg 291, pdf) that I am not quite understanding the
reasoning for the author's explanation:

if f1() or f2():

The author states that do to the nature of that expression, if f1()
returns True, f2() will not be evaluated.. which makes sense. His
quote:

        "Here, if f1 returns a true (or nonempty) value, Python will
never run f2."

He then states:

        "To guarantee that both functions will be run, call them
before the 'or':"

tmp1, tmp2 = f1(), f2()
if tmp1 or tmp2:

Being that each function is an object, a name assignment to
(tmp1,tmp2) doesn't actually evaluate or run the function itself until
the name is called.. so why would the latter example "run" both
functions as the author suggests?