Python：新 Object 丢失数组属性

Question

I'm currently writing a python programm that should create an array of class objects, which a have created.

The problem I'm facing is, that the class has an array as attribute. After I do myArray.clear() the class object loses the array values. The other values doesn't get lost. I know this is due to the reference of the array, but I don't know how to fix this.

Code example:

Class

class Testclass(object):
   def __init__(self, array, normalValue):
    self._array= array
    self._normalValue= normalValue
    

Main

if __name__=="main":
   exampleIteratorArray = ["Ex1", "Ex2", "Ex3"]
   objectArray = []
   for i, value in enumerate(exampleIteratorArray):
         exampleArray = [i, i+1, i+2]
         objectArray.append(Testclass(exampleArray, value))
         exampleArray.clear()              #I have to do this because I want to check the state depending on the value of this variable (in my main code)
                                            #After the exampleArray.clear(), the objectArray loses the exampleArray values but not the i value

Therefore, I wanted to know how I can add objects to the array without losing the values after each iteration. Thanks in advance: :)

Edit

As Azro pointed out, I create a new varaible from exampleArray every iteration therrefore I dont need to clear the array.

Answer 1

In Python, a list assignment refers to the same (original) instance of the list. When you clear the local array, you are clearing both the local array and the one you think you copied into the object (but actually didn't), since these are in fact the same array.

Simple example:

a = [1, 2, 3]
b = a
a.append(4)
print(b)
# prints [1, 2, 3, 4]

To assign / copy an array as a separate object, you need to use a copy or deep copy operation. A simple way in your current code would be a slice-to-copy:

objectArray.append(Testclass(exampleArray[:], value))

Note the [:] added.