Thanks; your answer explained it. I don't understand why Python works
that way, but I'll bet there's a good reason.
regards
john perry
On Oct 6, 12:14 pm, Mike Hansen <mhan...@gmail.com> wrote:
> Hello,
>
> On Wed, Oct 7, 2009 at 12:08 AM, john_perry_usm <john.pe...@usm.edu> wrote:
> > sage: f(yvar = xvar)
> > x^2 + y^2
> > sage: f({yvar:xvar})
> > 2*x^2
>
> > I was under the impression that both forms of substitution should
> > return the same thing, but apparently not. Can someone explain the
> > distinction to me?
>
> Doing f(yvar=xvar) is basically equivalent to doing f({'yvar':xvar})
> because of the way keyword arguments in Python work. Since, 'yvar' is
> being passed in as a string, the best that Sage could hope for is that
> there is a variable with the name "yvar". Since there isn't, then no
> substitution is done. When you call it the other way, the function
> gets the actual object that yvar refers to and is able to make the
> correct substitution.
>
> --Mike
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