S/sympify only work with valid Python code. A Symbol name can contain
any string, but it will only be parsable in a larger expression if it
is a valid Python name.
You can try using parse_expr from sympy.parsing.sympy_parser. It is
designed to parse some things that aren't valid Python. However, as
far as I know, it hasn't been designed to work with non-Python
variable names, so it would probably need some extension to work with
this.
The other way that always works is to wrap the name with Symbol, like
sympify("Symbol('a_{2, 2}')"). You also need do some extra things to
parse the =.
Aaron Meurer
On Mon, Dec 18, 2017 at 7:01 PM, Peter Brady <[email protected]> wrote:
> Hello all,
> I'm trying to parse expressions with multiple subscripts and am running into
> errors.
> For example, the following works:
>
> sympy.symbol("a_{2,2}")
>
> But parsing an expression does not:
>
> sympy.S("a_{2,2} = a_{3,1}+2")
>
> Can someone explain how to make this work?
>
> Thanks,
> Peter.
>
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