Push Operation on Stack in DSA Python - Practice Problems & Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output after pushing elements on a stack?

Consider the following Python code that uses a list as a stack. What will be the printed output after all push operations?

DSA Python

stack = []
stack.append(5)
stack.append(10)
stack.append(15)
print(stack)

A [5, 15, 10]

B [15, 10, 5]

C [5, 10, 15]

D [10, 5, 15]

💡 Hint

Remember that append adds elements to the end of the list.

The append method adds elements to the end of the list, so the stack will be [5, 10, 15].

❓ Predict Output

intermediate

What is the top element after pushing on stack?

After pushing elements 3, 7, and 9 on an empty stack, what is the top element of the stack?

DSA Python

stack = []
stack.append(3)
stack.append(7)
stack.append(9)
top = stack[-1]
print(top)

A 9

B 7

C None

D 3

💡 Hint

The top element is the last one pushed.

The last element pushed is 9, so stack[-1] is 9.

🔧 Debug

advanced

Identify the error in this push operation code

What error will this code produce when trying to push an element onto the stack?

DSA Python

stack = []
stack.push(4)
print(stack)

A No error, output: [4]

B AttributeError: 'list' object has no attribute 'push'

C IndexError: list index out of range

D TypeError: push() missing 1 required positional argument

💡 Hint

Check the method name for adding elements to a list.

Python lists use append() to add elements, not push(). Using push() causes AttributeError.

❓ Predict Output

advanced

What is the stack content after multiple push operations?

Given this code, what is the final stack content printed?

DSA Python

stack = [1, 2]
stack.append(3)
stack.append(4)
stack.append(5)
print(stack)

A [3, 4, 5]

B [5, 4, 3, 2, 1]

C [1, 2, 5, 4, 3]

D [1, 2, 3, 4, 5]

💡 Hint

Appending adds elements to the end of the list.

Appending adds elements at the end, so the stack grows as [1, 2, 3, 4, 5].

🧠 Conceptual

expert

What is the time complexity of the push operation on a stack implemented with a Python list?

Choose the correct time complexity for the push operation (adding an element) on a stack implemented using a Python list with append().

A O(1) - Constant time

B O(n) - Linear time

C O(log n) - Logarithmic time

D O(n^2) - Quadratic time

💡 Hint

Appending to the end of a Python list is usually very fast.

Python list append() runs in average constant time O(1) because it adds element at the end.