Array Deletion at Beginning in DSA Python - Interactive Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to remove the first element from the list.

DSA Python

arr = [1, 2, 3, 4]
arr.[1]  # Remove first element
print(arr)

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

Aremove(0)

Bdel

Cpop()

Dpop(0)

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop() removes the last element, not the first.

Using remove(0) tries to remove the value 0, not the first element.

Using pop(0) removes the first element from the list.

2fill in blank

medium

Complete the code to delete the first element using the del statement.

DSA Python

arr = [10, 20, 30, 40]
del arr[1]  # Delete first element
print(arr)

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

A(0)

B[0]

C{0}

D<0>

Attempts:

3 left

💡 Hint

Common Mistakes

Using parentheses or curly braces instead of square brackets.

Trying to delete without specifying the index.

The del statement deletes the element at index 0 using square brackets.

3fill in blank

hard

Fix the error in the code to remove the first element correctly.

DSA Python

arr = [5, 6, 7, 8]
arr.[1](arr[0])  # Remove first element
print(arr)

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

Adel

Bpop

Cremove

Ddelete

Attempts:

3 left

💡 Hint

Common Mistakes

Using pop with a value instead of an index causes an error.

Using del as a method is incorrect.

The remove method removes the first occurrence of the given value.

4fill in blank

hard

Fill in the blank to create a new list without the first element.

DSA Python

arr = [9, 8, 7, 6]
new_arr = arr[1]  # New list without first element
print(new_arr)

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

A[1:]

B[:1]

C[0:]

D[:]

Attempts:

3 left

💡 Hint

Common Mistakes

Using [:1] returns only the first element, not the rest.

Using [0:] returns the whole list, no deletion.

Slicing with [1:] creates a new list starting from index 1 to the end.

5fill in blank

hard

Fill both blanks to remove the first element and print the updated list.

DSA Python

arr = [100, 200, 300, 400]
arr.[1]([2])  # Remove first element
print(arr)

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

Apop

B0

Dremove

Attempts:

3 left

💡 Hint

Common Mistakes

Using remove with an index causes an error.

Adding parentheses inside print incorrectly.

Using pop(0) removes the first element. Printing arr shows the updated list.

Practice

1. What happens to an array when you delete the first element in Python using del arr[0]?

easy

A. The first element is removed and the rest shift left by one position.

B. The last element is removed instead of the first.

C. The array becomes empty regardless of its size.

D. The array remains unchanged.

Solution

1. Step 1: Understand del arr[0] operation

   This command removes the element at index 0, which is the first element of the array.

2. Step 2: Effect on the array

   After deletion, all elements after the first shift one position to the left to fill the gap.

3. Final Answer:

   The first element is removed and the rest shift left by one position. -> Option A

4. Quick Check:

   Deleting first element shifts others left [OK]

Hint: Deleting index 0 removes first element and shifts left [OK]

Common Mistakes:

• Thinking last element is removed
• Assuming array becomes empty
• Believing array stays the same

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

easy

A. del arr(0)

B. del arr[0]

C. arr.delete(0)

D. arr.remove(0)

Solution

1. Step 1: Check Python syntax for deleting by index

   Python uses del arr[index] to delete element at a specific index.

2. Step 2: Analyze options

   del arr[0] uses correct syntax del arr[0]. del arr(0) uses parentheses which is invalid. arr.delete(0) uses a method that does not exist. arr.remove(0) removes by value, not index.

3. Final Answer:

   del arr[0] -> Option B

4. Quick Check:

   Use del with square brackets for index deletion [OK]

Hint: Use del with square brackets to delete by index [OK]

Common Mistakes:

• Using parentheses instead of square brackets
• Confusing remove() with delete by index
• Trying to call a non-existent delete() method

3. What is the output of the following code?

arr = [10, 20, 30, 40]
del arr[0]
print(arr)

medium

A. [20, 30, 40]

B. [10, 20, 30]

C. [30, 40]

D. [10, 20, 30, 40]

Solution

1. Step 1: Delete first element from array

   The command del arr[0] removes the element 10 at index 0.

2. Step 2: Remaining elements shift left

   After deletion, the array becomes [20, 30, 40].

3. Final Answer:

   [20, 30, 40] -> Option A

4. Quick Check:

   First element removed, rest shifted left [OK]

Hint: Deleting index 0 removes first element, print rest [OK]

Common Mistakes:

• Expecting first element to remain
• Confusing deletion with removing last element
• Printing original array without deletion

4. Find the error in the code below that tries to delete the first element of the list arr:

arr = [5, 10, 15]
arr.delete(0)
print(arr)

medium

A. The print statement is incorrect.

B. The index 0 is out of range.

C. The list is empty, so deletion fails.

D. The method delete() does not exist for lists.

Solution

1. Step 1: Check list methods for deletion

   Python lists do not have a method called delete(). Deletion by index uses del keyword or pop() method.

2. Step 2: Identify correct deletion method

   To delete first element, use del arr[0] or arr.pop(0). Using arr.delete(0) causes AttributeError.

3. Final Answer:

   The method delete() does not exist for lists. -> Option D

4. Quick Check:

   Use del or pop, not delete() [OK]

Hint: Lists have no delete() method; use del or pop [OK]

Common Mistakes:

• Using delete() method on list
• Assuming delete() works like in other languages
• Ignoring AttributeError from wrong method

5. You have an array arr = [1, 2, 3, 4, 5]. You want to delete the first element and then add 0 at the beginning. Which code correctly does this in Python?

hard

A. arr.remove(0)
arr.insert(0, 0)
print(arr)

B. arr.pop(0)
arr.append(0)
print(arr)

C. del arr[0]
arr.insert(0, 0)
print(arr)

D. del arr[1]
arr.insert(0, 0)
print(arr)

Solution

1. Step 1: Delete first element correctly

   Using del arr[0] removes the first element (1) from the array.

2. Step 2: Insert 0 at the beginning

   Using arr.insert(0, 0) adds 0 at index 0, shifting others right.

3. Step 3: Check other options

   arr.pop(0) arr.append(0) print(arr) appends 0 at the end, not beginning. arr.remove(0) arr.insert(0, 0) print(arr) tries to remove value 0 which is not in array. del arr[1] arr.insert(0, 0) print(arr) deletes second element, not first.

4. Final Answer:

   del arr[0] arr.insert(0, 0) print(arr) -> Option C

5. Quick Check:

   Delete first, then insert at start [OK]

Hint: Delete index 0, then insert new element at index 0 [OK]

Common Mistakes:

• Appending instead of inserting at start
• Removing value 0 instead of index 0
• Deleting wrong index