On 20/10/2021 12:36, Oscar Benjamin wrote:
On Tue, 19 Oct 2021 at 20:55, David Bailey<d...@dbailey.co.uk> wrote:
Dear group,
First I would like to say how good it was to discover that the online
SymPy documentation now supports copy/paste operations without
constantly switching to SymPyLive. I think this will make the
documentation considerably more user friendly.
I'm not sure what has changed there...
Thanks for replying Oscar. You are right! When I went to the SymPy
documentation to prepare the second part of this email I found it
behaved in the same old way - maybe the live shell was down last night.
The problem is that if you click into a block of SymPy code with the
intention of cutting and pasting its contents, it fires up the live
shell when you don't want it - at least using Firefox on Windows 10. To
cut and paste you have to use a trick - clicking outside the block with
the green background and dragging into the block from there. Since there
is a dark green tag above each section to invoke the live shell, all
that is needed is to disable special trapping the left mouse click.
My question is what construct should I use to get variables with
subscripts, and maybe superscripts. I thought at first that indexed
objects were the way to go, but they seem rather obscure. E.g. think of
indexing through the Bessel functions - J0, J1,J2 etc.
Ideally I'd like to loop over the index/indices and also see the
subscripts positioned below the main symbol when using Latex output
I'm not completely sure what you want here but is this it:
In [19]: symbols('x:10')
Out[19]: (x₀, x₁, x₂, x₃, x₄, x₅, x₆, x₇, x₈, x₉)
IndexedBase is for the situation where you want the index to be symbolic e.g.:
In [27]: xi = IndexedBase('x')
In [28]: n, m = symbols('n, m')
In [29]: Sum(xi[n], (n, 1, m))
It was the second facility that I was looking for. What fooled me was
that in the documentation:
https://docs.sympy.org/latest/modules/tensor/indexed.html
The index variables are created specially:
i, j = symbols('i j', cls=Idx) However it would seem you can index with any integer variable.
What does the Idx class contribute? David
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