On Sat, Sep 18, 2010 at 8:54 PM, Nicholas Kinar <n.ki...@usask.ca> wrote:
>>
>>>> u = Dummy('u')
>
>
> I can't seem to use the u = Dummy('u') variable, since I now receive the
> following error:
>
> Traceback (most recent call last):
> File "test.py", line 12, in <module>
> u = Dummy('u')
> NameError: name 'Dummy' is not defined
I think that you need to use:
In [1]: a = Symbol("x", dummy=True)
>
> Moreover, I think that something like this would be extremely useful as a
> function incorporated into the sympy distribution:
>>>>
>>>> collect(expr2.subs([(a**(n+1), u*a**(n+1)) for a in _]), u)
If you have time, send us a patch for this please.
Btw --- you should not be using "from sympy import *", but rather use
explicit imports, then it would be clear where things are coming from
and also Python can guide you more when some imports change.
Ondrej
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