An example loop:

    elif cmd.op == 'TUPLE':
        arity, = cmd.args
        tuple_args = []
        for _ in range(arity):
            tuple_args.append(self.data_stack.pop())
        result = '{' + ', '.join(map(str, tuple_args)) + '}'
        self.data_stack.append(result)

Is following use of comprehension any better? I don't think so:

    elif cmd.op == 'TUPLE':
        arity, = cmd.args
        tuple_args = [str(arg) for arg in reversed(self.data_stack[-arity:])]
        self.data_stack = self.data_stack[:-arity]
        result = '{' + ', '.join(map(str, tuple_args)) + '}'
        self.data_stack.append(result)

Any other suggestions for improvement?