sys.getsizeof(list) returns less than the sum of its elements

Question

I\'m curious - why does the sys.getsizeof call return a smaller number for a list than the sum of its elements?

import sys
lst = [\"abcde\", \"fghij\", \"klmno\"         


        

Answer 1

The memory of a numpy array a can be obtained by a.nbytes.

sys.getsizeof shows "only the memory consumption directly attributed to the object [...], not the memory consumption of objects it refers to." (according to the documentation). In your case, it does not hold all the data. It can be seen with a.flags which outputs:

C_CONTIGUOUS : True
F_CONTIGUOUS : False
OWNDATA : False
WRITEABLE : True
ALIGNED : True
WRITEBACKIFCOPY : False
UPDATEIFCOPY : False

For the first array, it is instead:

C_CONTIGUOUS : True
F_CONTIGUOUS : False
OWNDATA : True
WRITEABLE : True
ALIGNED : True
WRITEBACKIFCOPY : False
UPDATEIFCOPY : False

The OWNDATA field being False explains why sys.getsizeof outputs only 128 bytes.