extract_variables

extract_variables(expr, prefix=None)

Extract variables of the form <prefix><digits> from a SymPy expression.

Examples

• prefix=None → returns all symbols like t1, x2, a10, grouped by (prefix, index)

• prefix=”t” → returns only t1, t2, …

Parameters:

• expr (Expr) – SymPy expression.

• prefix (str | None) – Optional prefix filter.

Returns:

list[Symbol] – Symbols sorted by (prefix, numeric index).

Return type:

list[Symbol]