Why doesn't list change?
Question:
In Python:
b = []
a = np.arange(2)
b.append(a)
a = np.arange(4)
b.append(a)
print(b) # gives [array([0, 1]), array([0, 1, 2, 3])]
Why doesn’t it give [array([0, 1, 2, 3]), array([0, 1, 2, 3])]?
There are a ton of questions going the other way (to make sure the list does not change — see here or this explanation on referencing and values).
From the links above I would expect b[0] == b[1] because I updated a, but this is not the case. What am I missing?
Answers:
a = np.arange(4) doesn’t update the values inside a, it reassigns the reference to a new array. This is reflected in b, as it has two different arrays as elements.
In Python:
b = []
a = np.arange(2)
b.append(a)
a = np.arange(4)
b.append(a)
print(b) # gives [array([0, 1]), array([0, 1, 2, 3])]
Why doesn’t it give [array([0, 1, 2, 3]), array([0, 1, 2, 3])]?
There are a ton of questions going the other way (to make sure the list does not change — see here or this explanation on referencing and values).
From the links above I would expect b[0] == b[1] because I updated a, but this is not the case. What am I missing?
a = np.arange(4) doesn’t update the values inside a, it reassigns the reference to a new array. This is reflected in b, as it has two different arrays as elements.