How to Create a Python Array of Objects and Ensure Separate Instances?

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1

How to Create a Python Array of Objects and Ensure Separate Instances?

I’m trying to create a list of objects in Python. Here’s my current code:

# Creating a Python object
class TestDat(object):
    Dat1 = None
    Dat2 = None

# Declaring the Test Array
TestArray = []

# Declaring the object
Test1 = TestDat()

# Defining the member variables in the object
Test1.Dat1 = 0
Test1.Dat1 = 1

# Appending the object to the List
TestArray.append(Test1)

# Rewriting and appending again
Test1.Dat1 = 3
Test1.Dat1 = 4
TestArray.append(Test1)

# Printing the Results
print TestArray[0].Dat1
print TestArray[1].Dat1

The output is 4 4, which means both elements in the list are referring to the same object. It seems like the append method is copying the reference to the object instead of creating a new instance.

How can I ensure that both elements in the array are different objects without creating a new object manually each time?

2

I’ve been working with Python for years, and creating separate instances in arrays can be tricky if you’re not careful. A simple way to ensure separate instances is by using list comprehensions. For example:

objects = [MyClass() for _ in range(5)]  # Creates 5 separate instances of MyClass

This approach ensures that each object in the array is distinct, avoiding unintended shared states.

3

Great point, Jacqueline! Another thing I’ve noticed in my experience is the importance of using factory functions or lambda expressions to make this more dynamic. For instance, you can do something like this:

objects = [(lambda: MyClass())() for _ in range(5)]

This guarantees each instance is separately created even if your class constructor involves some shared default states. Always a good idea to test these setups for unexpected behaviors!

4

Nice addition, Ishrath! I’d just like to expand a bit based on my experience handling complex objects. If your array involves objects with unique attributes or dependencies, you can add a bit more customization during creation.

For instance:

objects = [MyClass(param=i) for i in range(5)]  # Each instance gets unique attributes

This ensures both separation and individuality in attributes. And for larger projects, using object factories with dependency injection can keep things even cleaner. Just my two cents!