I have a class and its method. The method repeats many times during execution. This method uses a numpy array as a temporary buffer. I don't need to store values inside the buffer between method calls. Should I create a member instance of the array to avoid time leaks on memory allocation during the method execution? I know that it is preferred to use local variables. But is Python smart enough to allocate memory for the array only once?

class MyClass:def __init__(self, n):self.temp = numpy.zeros(n)def method(self):# do some stuff using self.temp

Or

class MyClass:def __init__(self, n):self.n = ndef method(self):temp = numpy.zeros(self.n)# do some stuff using temp

Update: replaced np.empty with np.zeros

Numpy arrays are fast, once created. However, creating an array is pretty expensive. Much more than, say, creating a python list.

In a case such as yours, where you create a new array again and again (in a for loop?), I would ALWAYS pre-allocate the array structure and then reuse it.

I can't comment on whether Python is smart enough to optimize this, but I would guess it's not :)

How big is your array and how frequent are calls to this method?