蚺蛇

还有像蟒蛇、蚺蛇这样的无毒蛇类。

Then there is non-venomous snakes like constrictors and pythons .

因此，如果说没有真正的无毒蛇类的话，那么像蟒蛇，蚺蛇这类所谓的无毒蛇类难道是在进化中由有毒进化为无毒吗？

So , if there are no truly non-venomous snakes , were the so-called non-venomous snakes , like constrictors and pythons , were they venomous at some point in their evolution ?