def evaluate(op, op_str, a, b, use_numexpr=True,<EOL>**eval_kwargs):
use_numexpr = use_numexpr and _bool_arith_check(op_str, a, b)<EOL>if use_numexpr:<EOL><INDENT>return _evaluate(op, op_str, a, b, **eval_kwargs)<EOL><DEDENT>return _evaluate_standard(op, op_str, a, b)<EOL>
evaluate and return the expression of the op on a and b

        Parameters
        ----------

        op :    the actual operand
        op_str: the string version of the op
        a :     left operand
        b :     right operand
        use_numexpr : whether to try to use numexpr (default True)