How do I create a new object for each class instance?

Question

Please look at the code snippet below, I asked the question below

class SAMPLES:
    x = np.zeros(10)

    def __init__(self, k, value):
        self.x[k] = value


a = SAMPLES(0, 9)
b = SAMPLES(0, 10)
print(a.x[0])
print(b.x[0])

OUTPUT:

10
10

But the output must be:

9
10

How should I solve this problem?

Put self.x = np.zeros(10) in the __init__ method. Using a class attribute shares the same array for all instances. — Barmar
– Barmar, Commented Jun 2, 2022 at 18:04
you're using a class variable but you want an instance variable. x has the same underlying data across all instances of SAMPLES. — jkr
– jkr, Commented Jun 2, 2022 at 18:04
x has been declared as a static variable instead of a instance variable. see this — Blackgaurd
– Blackgaurd, Commented Jun 2, 2022 at 18:04
I edited the title to better express the problem because at first glance I thought you were simply asking how to instantiate a class. But if you want to edit it further, by all means. Check out How to Ask if you want tips. — wjandrea
– wjandrea, Commented Jun 2, 2022 at 18:10
@wjandrea, Yes, the title you wrote is correct. thank you so much. — mehran
– mehran, Commented Jun 2, 2022 at 18:14

Blackgaurd · Accepted Answer · 2022-06-02 18:06:31Z

6

Declare x within the __init__ method.

class SAMPLES:
    def __init__(self, k, value):
        self.x = np.zeros(10)
        self.x[k] = value


a = SAMPLES(0, 9)
b = SAMPLES(0, 10)
print(a.x[0])
print(b.x[0])

answered Jun 2, 2022 at 18:06

Blackgaurd

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1 Comment

wjandrea Over a year ago

Correction: declare -> define. Python only has declarations for scope (global and nonlocal), which aren't being used here.

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