Array Insertion at End in DSA Python - Practice Problems & Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output after inserting elements at the end of the array?

Consider the following Python code that inserts elements at the end of an array (list). What will be printed?

DSA Python

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

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

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

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

D [1, 2, 3]

💡 Hint

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

The append method adds elements at the end of the list. So after appending 4 and 5, the list becomes [1, 2, 3, 4, 5].

❓ Predict Output

intermediate

What is the final array after multiple insertions at the end?

What will be the output of this code snippet?

DSA Python

arr = []
for i in range(3):
    arr.append(i * 2)
print(arr)

A [0, 1, 2]

B [0, 2, 4]

C [2, 4, 6]

D []

💡 Hint

Check the values generated by i * 2 for i in range(3).

The loop runs for i = 0, 1, 2. Multiplying by 2 gives 0, 2, 4. These are appended in order.

🔧 Debug

advanced

Identify the error in this array insertion code

What error will this code produce when run?

DSA Python

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

A No error, output: [1, 2, 3, 4, 5]

B SyntaxError: invalid syntax

C ValueError: too many values to unpack

D TypeError: append() takes exactly one argument (2 given)

💡 Hint

Check how many arguments append accepts.

The append method accepts only one argument. Passing two causes a TypeError.

🚀 Application

advanced

What is the array after inserting elements using extend?

Given the code below, what will be the final state of the array?

DSA Python

arr = [1, 2]
arr.extend([3, 4])
print(arr)

A [1, 2, 3, 4]

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

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

D [3, 4, 1, 2]

💡 Hint

Remember that extend adds each element of the iterable individually.

The extend method adds each element of the given list to the end of the original list.

🧠 Conceptual

expert

How many elements are in the array after these insertions?

If we start with an empty array and perform these operations, how many elements will the array have at the end? arr = [] arr.append(1) arr.append([2, 3]) arr.extend([4, 5])

A 4

B 5

C 3

D 6

💡 Hint

Remember append adds the whole object as one element, extend adds each element separately.

After append(1), array has 1 element.
append([2, 3]) adds the list as one element, total 2.
extend([4, 5]) adds two elements individually, total 4.

Practice

1. What does inserting an element at the end of an array mean?

easy

A. Replacing the first element with the new element

B. Adding the new element after the last existing element

C. Removing the last element and adding the new one at the start

D. Inserting the new element in the middle of the array

Solution

1. Step 1: Understand array structure

   An array stores elements in order, from first to last.

2. Step 2: Define insertion at end

   Inserting at the end means placing the new element after the last element, extending the array.

3. Final Answer:

   Adding the new element after the last existing element -> Option B

4. Quick Check:

   Insert at end = add after last element [OK]

Hint: End insertion means add after last element [OK]

Common Mistakes:

• Confusing insertion at end with replacing elements
• Thinking insertion means removing elements
• Mixing up start and end positions

2. Which of the following Python statements correctly inserts the value 10 at the end of list arr?

easy

A. arr.append(10)

B. arr.insert(0, 10)

C. arr.add(10)

D. arr[10] = 10

Solution

1. Step 1: Recall Python list methods

   To add an element at the end, use append() method.

2. Step 2: Check each option

   arr.append(10) uses append(10), which adds 10 at the end. Others either insert at start, use invalid method, or wrong syntax.

3. Final Answer:

   arr.append(10) -> Option A

4. Quick Check:

   append() adds at end [OK]

Hint: Use append() to add at end of list [OK]

Common Mistakes:

• Using insert(0, value) which adds at start
• Trying to assign value to arr[10] without index existing
• Using non-existent method add()

3. What will be the output of the following code?

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

medium

A. [1, 2, 3, 4]

B. Error

C. [1, 2, 3]

D. [4, 1, 2, 3]

Solution

1. Step 1: Understand initial array

   Array starts as [1, 2, 3].

2. Step 2: Apply append(4)

   Append adds 4 at the end, so array becomes [1, 2, 3, 4].

3. Final Answer:

   [1, 2, 3, 4] -> Option A

4. Quick Check:

   append(4) adds 4 at end [OK]

Hint: append() adds element at array's end [OK]

Common Mistakes:

• Thinking append adds at start
• Expecting original array unchanged
• Confusing append with insert

4. Find the error in the following code that tries to insert 5 at the end of the list nums:

nums = [1, 2, 3]
nums.insert(5)

medium

A. insert() cannot be used to add elements

B. nums is not a list

C. append() should be used instead of insert()

D. insert() requires two arguments: index and value

Solution

1. Step 1: Check insert() method signature

   insert() needs two arguments: position index and value to insert.

2. Step 2: Analyze given code

   Code calls insert(5) with only one argument, causing error.

3. Final Answer:

   insert() requires two arguments: index and value -> Option D

4. Quick Check:

   insert() needs index and value [OK]

Hint: insert() needs index and value arguments [OK]

Common Mistakes:

• Calling insert() with one argument
• Confusing insert() and append() usage
• Assuming insert() adds at end by default

5. You have an array arr = [2, 4, 6]. You want to add multiple elements [8, 10, 12] at the end efficiently. Which code snippet correctly does this?

hard

A. arr.append(8, 10, 12)

B. arr.append([8, 10, 12])

C. arr.extend([8, 10, 12])

D. arr.insert(len(arr), [8, 10, 12])

Solution

1. Step 1: Understand difference between append and extend

   append adds one element; extend adds all elements from iterable individually.

2. Step 2: Analyze options

   A: arr.append(8,10,12) passes multiple arguments to append(), causing TypeError. B: arr.append([8,10,12]) adds list as one element. arr.extend([8,10,12]) adds all elements individually at end. arr.insert(len(arr),[8,10,12]) inserts list as one element at end.

3. Final Answer:

   arr.extend([8, 10, 12]) -> Option C

4. Quick Check:

   extend() adds multiple elements at end [OK]

Hint: Use extend() to add multiple elements at once [OK]

Common Mistakes:

• Passing multiple arguments to append()
• Using append() to add list as single element
• Using insert() with list adds nested list