Checking if 1D numpy array in a list of 1D numpy arrays and None

Question

I want to check whether a 1D numpy array in the list of a 1D numpy arrays and None for an if condition.

I did it like this:

arr = np.array([1,2])
lst = [np.array([1,2]), np.array([3,4]), None, None]

if list(arr) in [list(i) for i in lst if i is not None]:
    print("Yes")

else:
    print("No")

but the size of the list and the numpy array can be much larger, so is there a more efficient way to do this? instead of changing every numpy array to list.

Answer 1

You cannot avoid one iteration through the lst to modify its elements (numpy arrays) somehow. But instead of creating a list of lists out of the numpy arrays, you can create a set of tuples instead and store it: set_of_arrays_as_tuples = set([tuple(array) for array in lst if array is not None])

Then, any subsequent query to check presence in the set can be done in constant time, instead of linear time:

tuple(arr) in set_of_arrays_as_tuples

->True