Object References and Side Effects
12345a = [1, 2, 3] b = a b.append(4) print("a:", a) print("b:", b)
When you assign a variable to a mutable object like a list, you are actually creating a reference to that object, not a new copy. In the code above, both a and b point to the same list in memory. This means that any change made to the list through b—such as appending the value 4—will also be reflected when accessing a. This behavior can lead to unexpected side effects, especially when you intend to have two separate lists.
To avoid this, you can create a copy of the list. There are several ways to do this in Python, such as using the list() constructor, slicing, or the copy() method. For example, if you want b to be a new list with the same contents as a, you can write b = a.copy(). Now, modifying b will not affect a, and vice versa. Understanding how references work is crucial for avoiding bugs related to shared mutable objects.
1. Which statement best describes what happens when two variables reference the same list in Python?
2. Arrange the code blocks in the correct order to copy a list so that modifying the new list does not affect the original.
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Can you show examples of how to properly copy a list?
What are other common pitfalls with mutable objects in Python?
Can you explain the difference between shallow and deep copies?
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12345a = [1, 2, 3] b = a b.append(4) print("a:", a) print("b:", b)
When you assign a variable to a mutable object like a list, you are actually creating a reference to that object, not a new copy. In the code above, both a and b point to the same list in memory. This means that any change made to the list through b—such as appending the value 4—will also be reflected when accessing a. This behavior can lead to unexpected side effects, especially when you intend to have two separate lists.
To avoid this, you can create a copy of the list. There are several ways to do this in Python, such as using the list() constructor, slicing, or the copy() method. For example, if you want b to be a new list with the same contents as a, you can write b = a.copy(). Now, modifying b will not affect a, and vice versa. Understanding how references work is crucial for avoiding bugs related to shared mutable objects.
1. Which statement best describes what happens when two variables reference the same list in Python?
2. Arrange the code blocks in the correct order to copy a list so that modifying the new list does not affect the original.
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