Array Deletion at End in DSA Python - Build from Scratch

Array Deletion at End

📖 Scenario: You are managing a list of tasks to do today. Sometimes, you finish the last task and want to remove it from your list.

🎯 Goal: Build a simple program that creates a list of tasks, removes the last task, and then shows the updated list.

📋 What You'll Learn

Create a list called tasks with these exact items: 'Laundry', 'Dishes', 'Homework', 'Exercise'

Create a variable called last_task that removes the last item from the tasks list

Print the updated tasks list after removing the last task

💡 Why This Matters

🌍 Real World

Managing daily to-do lists or any ordered collection where you often remove the last item, like undo stacks or recent files.

💼 Career

Understanding list operations like removing items from the end is fundamental for programming tasks in software development, data processing, and automation.

1

Create the initial list of tasks

Create a list called tasks with these exact items in order: 'Laundry', 'Dishes', 'Homework', 'Exercise'

DSA Python

# Create the list of tasks
# Your code here

Hint

Use square brackets [] to create a list and separate items with commas.

2

Remove the last task from the list

Create a variable called last_task that removes the last item from the tasks list using the pop() method

DSA Python

tasks = ['Laundry', 'Dishes', 'Homework', 'Exercise']
# Remove the last task and store it in last_task
# Your code here

Hint

The pop() method removes the last item from a list and returns it.

3

Print the updated list of tasks

Print the tasks list to show the tasks remaining after removing the last one

DSA Python

tasks = ['Laundry', 'Dishes', 'Homework', 'Exercise']
last_task = tasks.pop()
# Print the updated tasks list
# Your code here

Hint

Use print(tasks) to display the list.

4

Print the removed last task

Print the variable last_task to show which task was removed from the end

DSA Python

tasks = ['Laundry', 'Dishes', 'Homework', 'Exercise']
last_task = tasks.pop()
print(tasks)
# Print the removed last task
# Your code here

Hint

Use print(last_task) to show the removed task.

Practice

1. What happens when you delete the last element from an array in Python using pop()?

easy

A. The first element is removed and the array size stays the same.

B. The last element is removed and the array size decreases by one.

C. The array is cleared completely.

D. The array becomes empty but elements remain.

Solution

1. Step 1: Understand the pop() method

   The pop() method removes the last element from the array (list) by default.

2. Step 2: Effect on array size

   After removal, the array size decreases by one because one element is deleted.

3. Final Answer:

   The last element is removed and the array size decreases by one. -> Option B

4. Quick Check:

   pop() removes last element [OK]

Hint: pop() removes last item and shrinks array [OK]

Common Mistakes:

• Thinking pop() removes the first element
• Assuming pop() clears the whole array
• Believing array size stays the same after pop()

2. Which of the following is the correct syntax to delete the last element from a list named arr in Python?

easy

A. arr.pop()

B. arr.delete()

C. pop(arr)

D. arr.remove_last()

Solution

1. Step 1: Identify the correct method for deletion at end

   In Python, pop() is the method used to remove the last element from a list.

2. Step 2: Check syntax correctness

   The correct syntax is arr.pop(). Other options are invalid or do not exist in Python.

3. Final Answer:

   arr.pop() -> Option A

4. Quick Check:

   pop() is correct syntax [OK]

Hint: Use arr.pop() to remove last element [OK]

Common Mistakes:

• Using arr.delete() which is invalid
• Trying pop(arr) instead of arr.pop()
• Using arr.remove_last() which does not exist

3. What is the output of the following code?

arr = [10, 20, 30, 40]
arr.pop()
print(arr)

medium

A. [10, 20, 30]

B. [20, 30, 40]

C. [10, 20, 30, 40]

D. [10, 20, 40]

Solution

1. Step 1: Understand pop() effect on arr

   The pop() removes the last element, which is 40.

2. Step 2: Print the updated array

   After removal, the array becomes [10, 20, 30].

3. Final Answer:

   [10, 20, 30] -> Option A

4. Quick Check:

   Last element removed, array shrinks [OK]

Hint: pop() removes last element, print updated list [OK]

Common Mistakes:

• Expecting original array unchanged
• Removing first element instead of last
• Confusing pop() with remove()

4. Find the error in the following code that tries to delete the last element from arr:

arr = [1, 2, 3]
arr.pop(0)
print(arr)

medium

A. pop() deletes the entire array

B. pop() cannot take any arguments

C. pop() should be replaced with remove()

D. pop(0) removes the first element, not the last

Solution

1. Step 1: Analyze pop(0) usage

   pop(0) removes the element at index 0, which is the first element, not the last.

2. Step 2: Identify correct method to delete last element

   To delete the last element, pop() should be called without arguments.

3. Final Answer:

   pop(0) removes the first element, not the last -> Option D

4. Quick Check:

   pop(index) removes element at index [OK]

Hint: pop() without argument removes last element [OK]

Common Mistakes:

• Assuming pop() cannot take arguments
• Using pop(0) to remove last element
• Confusing pop() with remove()

5. Given the list arr = [5, 10, 15, 20, 25], you want to remove the last two elements using pop(). Which code snippet correctly achieves this?

hard

A. arr.pop(1)
arr.pop(0)

B. arr.pop(3)
arr.pop(2)

C. arr.pop()
arr.pop()

D. arr.pop(0)
arr.pop(1)

Solution

1. Step 1: Understand pop() without argument

   Calling pop() without arguments removes the last element each time.

2. Step 2: Apply pop() twice to remove last two elements

   Calling arr.pop() twice removes 25 then 20, the last two elements.

3. Step 3: Check other options

   Options A, B, and C use indices that become invalid or remove wrong elements after first pop.

4. Final Answer:

   arr.pop() followed by arr.pop() -> Option C

5. Quick Check:

   pop() twice removes last two elements [OK]

Hint: Use pop() twice to remove last two elements [OK]

Common Mistakes:

• Using pop() with fixed indices without updating
• Removing first elements instead of last
• Assuming pop() clears multiple elements at once