In python, which one is faster ?

numpy.max(), numpy.min()

or

max(), min()

My list/array length varies from 2 to 600. Which one should I use to save some run time ?

Well from my timings it follows if you already have numpy array a you should use a.max (the source tells it's the same as np.max if a.max available). But if you have built-in list then most of the time takes converting it into np.ndarray => that's why max is better in your timings.

In essense: if np.ndarray then a.max, if list and no need for all the machinery of np.ndarray then standard max.