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.