Assuming this numpy array is stored locally as an npy file, you could use np.load with the mmap_mode 5, which would allow you to load sliced from the disc without reading the whole array into memory:

mmap_mode {None, ‘r+’, ‘r’, ‘w+’, ‘c’}, optional
If not None, then memory-map the file, using the given mode (see numpy.memmap 1 for a detailed description of the modes). A memory-mapped array is kept on disk. However, it can be accessed and sliced like any ndarray. Memory mapping is especially useful for accessing small fragments of large files without reading the entire file into memory.