It does. What you have is the string form, which is designed to be
readable, but also copy-pastable. Like almost all SymPy objects, there
are pretty printers for Subs, including ASCII, Unicode, and LaTeX.
For ASCII/Unicode, you get the bar notation:
In [3]: pprint(Subs(diff(f(x), x), x, 0))
⎛d ⎞│
⎜──(f(x))⎟│
⎝dx ⎠│x=0
In LaTeX, you get
In [1]: latex(Subs(f(x), x, 0))
Out[1]: \left. \operatorname{f}{\left (x \right )} \right|_{\substack{ x=0 }}
which is the same thing. If you want this in the IPython notebook,
just use the SymPy printing extension, which will make everything
print with LaTeX using MathJax. Just run
%load_ext sympy.interactive.ipythonprinting
at the top of the notebook (init_printing(use_latex=True) should work too).
Aaron Meurer
On Sat, Jan 19, 2013 at 10:00 AM, David Ketcheson <dke...@gmail.com> wrote:
> Thanks, Aaron. That works, though I had hoped for something prettier than:
>
> Subs(Derivative(f(_x), _x), (_x,), (x0,))
>
> It would be really great if sympy knew how to print this kind of thing
> nicely (say, in an IPython notebook).
>
> -David
>
> On Wed, Jan 16, 2013 at 9:25 PM, Aaron Meurer <asmeu...@gmail.com> wrote:
>>
>> Try Subs(diff(f, x), x, x0).
>>
>> Note that mathematically, this should be the same as diff(f,
>> x).subs(x, x0), because x is a bound (not free) variable in this
>> expression, it doesn't matter if a different one is used, or if an
>> expression is used that doesn't use it at all. Note that if you use a
>> non-variable instead of x0, it will automatically give you the Subs
>> form (in particular, if you use a number, like diff(f, x).subs(x,
>> 10)). It will also give you the Subs form if you later substitute x0
>> for a number (in terms of x0, but it doesn't matter because x0 serves
>> as a dummy variable in this case).
>>
>> Aaron Meurer
>>
>> On Wed, Jan 16, 2013 at 5:06 AM, David Ketcheson <dke...@gmail.com> wrote:
>> > Is there any way in sympy to express the derivative of an abstract
>> > function
>> > evaluated at a point? I can do
>> >
>> > import sympy
>> > x,x0 = sympy.var(('x','x0'))
>> > f=sympy.Function('f') (x)
>> > sympy.diff(f)
>> >
>> > to get the derivative w.r.t. x evaluated at x. If I do
>> >
>> > sympy.diff(f).subs(x,x0)
>> >
>> > then I get the derivative w.r.t. x0 evaluated at x0. Can I get the
>> > derivative w.r.t. x evaluated at x0?
>> >
>> > --
>> > You received this message because you are subscribed to the Google
>> > Groups
>> > "sympy" group.
>> > To view this discussion on the web visit
>> > https://groups.google.com/d/msg/sympy/-/cQScvWEPp9MJ.
>> > To post to this group, send email to sympy@googlegroups.com.
>> > To unsubscribe from this group, send email to
>> > sympy+unsubscr...@googlegroups.com.
>> > For more options, visit this group at
>> > http://groups.google.com/group/sympy?hl=en.
>>
>> --
>> You received this message because you are subscribed to the Google Groups
>> "sympy" group.
>> To post to this group, send email to sympy@googlegroups.com.
>> To unsubscribe from this group, send email to
>> sympy+unsubscr...@googlegroups.com.
>> For more options, visit this group at
>> http://groups.google.com/group/sympy?hl=en.
>>
>
> --
> You received this message because you are subscribed to the Google Groups
> "sympy" group.
> To post to this group, send email to sympy@googlegroups.com.
> To unsubscribe from this group, send email to
> sympy+unsubscr...@googlegroups.com.
> For more options, visit this group at
> http://groups.google.com/group/sympy?hl=en.
--
You received this message because you are subscribed to the Google Groups
"sympy" group.
To post to this group, send email to sympy@googlegroups.com.
To unsubscribe from this group, send email to
sympy+unsubscr...@googlegroups.com.
For more options, visit this group at
http://groups.google.com/group/sympy?hl=en.
