Python Coding challenge — Day 242 | What is the output of the following Python Code?

Let’s break down the code step by step:

Code Explanation:

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

Step 1: a = [1, 2, 3]

• This creates a list a containing the elements [1, 2, 3].

Step 2: b = a[:]

• The [:] syntax creates a shallow copy of the list a.
• This means that b will be a new list with the same elements as a but stored in a different memory location.
• After this line, b contains [1, 2, 3].

Step 3: a.append(4)

• The append() method adds the element 4 to the end of the list a.
• Now, a contains [1, 2, 3, 4].
• However, since b is a separate list (created by the shallow copy), it remains unchanged.

Step 4: print(b)

• When you print b, it outputs [1, 2, 3], because b was not modified when a was appended with 4.

Summary:

• The key point is that b is a separate copy of the list a at the time of copying. Any subsequent modifications to a do not affect b.
• The final output of the code is [1, 2, 3].