On Thu, 11 Feb 2021 at 11:19, Thomas Ligon <[email protected]> wrote:
>
> "The solution to this in Python is to use lists or tuples or some other
> container rather than raw variables. For example:
>
> x = symbols('x:10')"
>
> Based on that, and
> Core — SymPy 1.7.1 documentation
>
> a = symbols('a:2*maxIter+1')
>
> The result is
>
> (a0*maxIter+1, a1*maxIter+1)
>
> The problem is that symbols does not support variables after the colon,
> defeating the whole purpose of using indexed symbols to begin with.
You can use the features of the Python language to generate the string
as input to the symbols function:
>>> num_symbols = 10
This is using %-formatting of strings:
>>> 'x:%d' % num_symbols
'x:10'
>>> symbols('x:%d' % num_symbols)
(x0, x1, x2, x3, x4, x5, x6, x7, x8, x9)
This is using f-strings:
>>> f'x:{num_symbols}'
'x:10'
>>> symbols(f'x:{num_symbols}')
(x0, x1, x2, x3, x4, x5, x6, x7, x8, x9)
> I am trying to use indexed symbols.
Note that "indexed symbols" means something different in sympy e.g.:
>>> from sympy import IndexedBase
>>> x = IndexedBase('x')
>>> x
x
>>> x[0]
x[0]
IndexedBase represents a mathematical quantity that can be subscripted
but in a symbolic way. For example if I have some data points that I
refer to as x_1, x_2, etc. and I want to refer to x_i then I can use
IndexedBase and index it with a symbol.
Oscar
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