https://github.com/sympy/sympy/issues/9135
On Tuesday, May 19, 2015 at 2:33:03 PM UTC-6, Jonathan Lindgren wrote:
>
> Well, that is exactly the problem, and what I think is a bug....it should
> not work like that..
>
> Den tisdag 19 maj 2015 kl. 22:00:46 UTC+2 skrev Alexander Lindsay:
>>
>> Not to hijack this post, but why does subs(phi(z,t).diff(z),...) work
>> when phi(z,t).diff(t,2) does not contain any derivatives of phi with
>> respect to z? It seems like this substitution is saying that
>> phi(z,t).diff(z) = phi(z,t)
>>
>> I'm new to sympy, so I apologize if this is a stupid question.
>>
>> Alex
>>
>> On 05/19/2015 12:16 PM, Jonathan Lindgren wrote:
>>
>> I recently updated from sympy 0.7.4 (I tihnk) to 0.7.6 and now I have
>> some very strange behaviour with subs. The following code
>>
>> from sympy.abc import phi
>> import sympy as sp
>>
>> z=sp.Symbol('z')
>> t=sp.Symbol('t')
>>
>> sp.pprint((phi(z,t).diff(t,2)).subs(phi(z,t).diff(z),sp.Symbol('b')(z,t)).expand())
>>
>>
>> gives me the output
>> 2
>> ∂
>> ───(b(z, t))
>> 2
>> ∂t
>> but I would expect the output
>> 2
>> ∂
>> ───(φ(z, t))
>> 2
>> ∂t
>>
>> This was working perfectly in my previous version of sympy.
>> --
>> You received this message because you are subscribed to the Google Groups
>> "sympy" group.
>> To unsubscribe from this group and stop receiving emails from it, send an
>> email to [email protected].
>> To post to this group, send email to [email protected].
>> Visit this group at http://groups.google.com/group/sympy.
>> To view this discussion on the web visit
>> https://groups.google.com/d/msgid/sympy/a50b1e03-3c37-4207-bc4b-7b6663c80c84%40googlegroups.com
>>
>> <https://groups.google.com/d/msgid/sympy/a50b1e03-3c37-4207-bc4b-7b6663c80c84%40googlegroups.com?utm_medium=email&utm_source=footer>
>> .
>> For more options, visit https://groups.google.com/d/optout.
>>
>>
>>
--
You received this message because you are subscribed to the Google Groups
"sympy" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To post to this group, send email to [email protected].
Visit this group at http://groups.google.com/group/sympy.
To view this discussion on the web visit
https://groups.google.com/d/msgid/sympy/969df696-5a5b-4389-8d49-14117b602927%40googlegroups.com.
For more options, visit https://groups.google.com/d/optout.
