Comparing object ids of two numpy arrays

Question

I have been using numpy for quite a while but I stumbled upon one thing that I didn\'t understand fully:

a = np.ones(20)
b = np.zeros(10)

print         


        

Answer 1

It's important to note that everything in Python is an object, even numbers and Classes. You have taken 2 numpy array object and each of contains same values i.e 0. When you say:

print('id of 0 =',id(0))

a = 0
print('id of a =',id(a))

b = a
print('id of b =',id(b))

c = 0.0
print('id of c =',id(c))

The answer you get something like (your case it's different):

id of 0 = 140472391630016
id of a = 140472391630016
id of b = 140472391630016
id of c = 140472372786520

Hence, integer 0 has a unique id. The id of the integer 0 remains constant during the lifetime. Similar is the case for float 0.0 and other objects. So in your case a[0] or b[0] object id of zero will remain same until or unless it is alive because both contains 0 as object value. Each time you print a[0] or b[0] in different line you return it's different identity of object because you triggering it at different line hence different lifetime. You can try:

print(id(a)==id(b))
print(id(a),id(b))
print(id(a[0])==id(b[0]))
print(id(a[0]),id(b[0]))

The output will be:

False
2566443478752 2566448028528
True
2566447961120 2566447961120

Note that second line will return to you 2 different identity of object of numpy array type because both are different list.