Array Insertion at Beginning in DSA Python - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to insert an element at the beginning of the list.

DSA Python

arr = [2, 3, 4]
arr.[1](0, 1)
print(arr)

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

Ainsert

Bextend

Cpop

Dappend

Attempts:

3 left

💡 Hint

Common Mistakes

Using append adds at the end, not the beginning.

Using pop removes elements instead of adding.

The insert method adds an element at a specific index. Here, index 0 means the beginning.

2fill in blank

medium

Complete the code to insert the value 10 at the start of the list named numbers.

DSA Python

numbers = [20, 30, 40]
numbers.[1](0, 10)
print(numbers)

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

Apop

Bappend

Cremove

Dinsert

Attempts:

3 left

💡 Hint

Common Mistakes

Using append adds at the end.

Using remove or pop deletes elements.

To add 10 at the start, use insert(0, 10) on the list.

3fill in blank

hard

Fix the error in the code to correctly insert 5 at the beginning of the list.

DSA Python

data = [6, 7, 8]
data.[1](0, 5)
print(data)

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

Aappend

Binsert

Cextend

Dpop

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping the order of arguments causes wrong insertion.

Using append adds at the end.

The insert method requires the index first, then the value. So it should be insert(0, 5).

4fill in blank

hard

Fill both blanks to insert 100 at the start and then print the list.

DSA Python

lst = [200, 300]
lst.[1]([2], 100)
print(lst)

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

Ainsert

Bappend

C0

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using append instead of insert.

Using wrong index like 1 instead of 0.

Use insert with index 0 to add at the beginning.

5fill in blank

hard

Fill all three blanks to insert 0 at the beginning, then insert 5 at index 1, and finally print the list.

DSA Python

arr = [10, 15]
arr.[1]([2], 0)
arr.[3](1, 5)
print(arr)

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

Ainsert

Bappend

C0

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using append instead of insert.

Mixing up indices.

Use insert(0, 0) to add 0 at start, then insert(1, 5) to add 5 at index 1.

Practice

1. What does inserting an element at the beginning of an array do to the existing elements?

easy

A. Shifts all existing elements one position to the right

B. Deletes the last element of the array

C. Replaces the first element with the new element

D. Leaves the array unchanged

Solution

1. Step 1: Understand array insertion at beginning

   When we insert at the start, the new element takes index 0.

2. Step 2: Effect on existing elements

   All existing elements move one position right to make space.

3. Final Answer:

   Shifts all existing elements one position to the right -> Option A

4. Quick Check:

   Insert at start = shift right [OK]

Hint: New start means shift all right by one [OK]

Common Mistakes:

• Thinking insertion replaces first element
• Assuming array size shrinks
• Believing array stays unchanged

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

easy

A. arr.add(10)

B. arr.append(10)

C. arr[0] = 10

D. arr.insert(0, 10)

Solution

1. Step 1: Identify correct method for insertion at index

   Python list method insert(index, value) inserts at given index.

2. Step 2: Check each option

   arr.insert(0, 10) uses insert(0, 10) which inserts 10 at start. Others either append at end, replace element, or invalid method.

3. Final Answer:

   arr.insert(0, 10) -> Option D

4. Quick Check:

   Use insert(0, value) to add at start [OK]

Hint: Use insert(0, value) to add at beginning [OK]

Common Mistakes:

• Using append() adds at end, not start
• Assigning arr[0] replaces element, no shift
• Using non-existent method add()

3. What is the output of the following code?

arr = [2, 3, 4]
arr.insert(0, 1)
print(arr)

medium

A. [1, 3, 4]

B. [2, 3, 4, 1]

C. [1, 2, 3, 4]

D. [2, 3, 4]

Solution

1. Step 1: Initial array and insertion

   Original array is [2, 3, 4]. Using insert(0, 1) adds 1 at index 0.

2. Step 2: Resulting array after insertion

   All elements shift right. New array is [1, 2, 3, 4].

3. Final Answer:

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

4. Quick Check:

   Insert at start shifts elements right [OK]

Hint: Insert at 0 puts element first, shifts others [OK]

Common Mistakes:

• Thinking insert adds at end
• Replacing first element instead of shifting
• Ignoring shift effect on elements

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

nums = [10, 20, 30]
nums.add(5)
print(nums)

medium

A. Method add() does not exist for lists

B. The list nums is empty

C. The print statement is incorrect

D. The value 5 cannot be inserted into a list

Solution

1. Step 1: Check method used for insertion

   Python lists do not have an add() method; this causes an error.

2. Step 2: Correct method to insert at beginning

   Use insert(0, 5) to add 5 at start of list.

3. Final Answer:

   Method add() does not exist for lists -> Option A

4. Quick Check:

   Use insert() not add() for list insertion [OK]

Hint: Use insert() for lists, add() is invalid [OK]

Common Mistakes:

• Assuming add() works like append()
• Thinking print statement causes error
• Believing list cannot hold new values

5. Given the list data = [4, 5, 6], which code snippet correctly inserts the elements of another list new_items = [1, 2, 3] at the beginning so that the final list is [1, 2, 3, 4, 5, 6]?

hard

A. for item in new_items:
data.insert(0, item)

B. for item in reversed(new_items):
data.insert(0, item)

C. data.extend(new_items)

D. data.append(new_items)

Solution

1. Step 1: Understand insertion order impact

   Inserting each item at index 0 shifts existing elements right. To keep order, insert reversed list.

2. Step 2: Analyze each option

   for item in new_items: data.insert(0, item) inserts 1, then 2 at front, reversing order. for item in reversed(new_items): data.insert(0, item) inserts reversed list, preserving order. Options C and D add at end or nested list.

3. Final Answer:

   for item in reversed(new_items): data.insert(0, item) -> Option B

4. Quick Check:

   Insert reversed to keep order at start [OK]

Hint: Insert reversed list at 0 to keep order [OK]

Common Mistakes:

• Inserting forward order reverses new items
• Using extend() adds at end, not start
• Appending list nests it inside