Pop Operation on Stack in DSA Python - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to remove the top element from the stack.

DSA Python

def pop(stack):
    if not stack:
        return None
    return stack[1]()

Drag options to blanks, or click blank then click option'

Aappend

Bpop

Cremove

Dinsert

Attempts:

3 left

💡 Hint

Common Mistakes

Using append() which adds an element instead of removing.

Using remove() which removes by value, not by position.

The pop() method removes and returns the last item from the list, which is the top of the stack.

2fill in blank

medium

Complete the code to check if the stack is empty before popping.

DSA Python

def safe_pop(stack):
    if len(stack) [1] 0:
        return stack.pop()
    return None

Drag options to blanks, or click blank then click option'

A==

B!=

C<

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using '==' which only checks if stack is exactly zero.

Using '<' which checks for less than zero, impossible for length.

We check if the stack length is greater than 0 before popping to avoid errors.

3fill in blank

hard

Fix the error in the pop function to correctly remove the top element.

DSA Python

def pop_element(stack):
    if stack:
        return stack[1]()
    return None

Drag options to blanks, or click blank then click option'

Aappend

Bremove

Cpop

Dinsert

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop(0) which removes the bottom element.

Using remove() which removes by value, not position.

Using pop() without arguments removes the last element (top of stack). pop(0) removes the first element, which is incorrect for stack.

4fill in blank

hard

Fill both blanks to create a function that pops the top element and returns the updated stack.

DSA Python

def pop_and_return(stack):
    if stack:
        stack[1]()
    return [2]

Drag options to blanks, or click blank then click option'

Apop

Bstack

CNone

Dappend

Attempts:

3 left

💡 Hint

Common Mistakes

Returning None instead of the updated stack.

Using append() which adds elements instead of removing.

Calling pop() removes the top element. Returning stack shows the updated stack.

5fill in blank

hard

Fill all three blanks to pop the top element only if the stack is not empty and return the popped element.

DSA Python

def conditional_pop(stack):
    if len(stack) [1] 0:
        return stack[2]()
    else:
        return [3]

Drag options to blanks, or click blank then click option'

A>

Bpop

CNone

D==

Attempts:

3 left

💡 Hint

Common Mistakes

Using '==' instead of '>' to check stack length.

Returning stack instead of None when empty.

Check if stack length is greater than 0, then pop the top element. Otherwise, return None.