Python List Methods (Part 3)

Python provides several methods and functions to remove elements, reverse lists, sort data, and perform mathematical operations. These methods are widely used while processing numerical data and solving real-world programming problems.

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Learning Objectives

• Remove elements from a list.
• Reverse and sort a list.
• Understand the difference between sort() and sorted().
• Find minimum, maximum, and sum of list elements.

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1. remove() Method

The remove() method removes the first occurrence of the specified element from a list.

Syntax

list.remove(element)

Example

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

Output

[10,30,20,40]

Explanation: Only the first occurrence of 20 is removed.

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Important Note

If the specified element is not present in the list, Python raises a ValueError.

numbers=[10,20,30]
numbers.remove(50)

Output

ValueError

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2. pop() Method

The pop() method removes and returns an element from the specified index. If no index is provided, it removes the last element.

Syntax

list.pop(index)

Example 1

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

Output

[10,20,30]

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Example 2

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

Output

[10,30,40]

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Difference between remove() and pop()

remove()	pop()
Removes by value.	Removes by index.
Returns nothing.	Returns the removed element.
Raises ValueError if value is absent.	Raises IndexError for an invalid index.

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3. reverse() Method

The reverse() method reverses the order of elements in the original list.

Syntax

list.reverse()

Example

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

Output

[40,30,20,10]

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4. sort() Method

The sort() method arranges the elements of the original list in ascending order by default.

Syntax

list.sort()

Example

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

Output

[10,20,30,40]

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Descending Order

numbers=[40,10,30,20]
numbers.sort(reverse=True)
print(numbers)

Output

[40,30,20,10]

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5. sorted() Function

The sorted() function returns a new sorted list without modifying the original list.

Syntax

sorted(list)

Example

numbers=[40,10,30,20]
newlist=sorted(numbers)
print(numbers)
print(newlist)

Output

[40,10,30,20]
[10,20,30,40]

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Difference between sort() and sorted()

sort()	sorted()
Modifies the original list.	Returns a new sorted list.
Works only with lists.	Works with many iterable objects.
Returns None.	Returns a sorted list.

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6. min() Function

The min() function returns the smallest element from a list.

Syntax

min(list)

Example

marks=[85,90,72,96]
print(min(marks))

Output

72

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7. max() Function

The max() function returns the largest element from a list.

Syntax

max(list)

Example

marks=[85,90,72,96]
print(max(marks))

Output

96

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8. sum() Function

The sum() function returns the sum of all numeric elements in a list.

Syntax

sum(list)

Example

marks=[85,90,72,96]
print(sum(marks))

Output

343

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Summary Table

Function / Method	Purpose
remove()	Removes the first matching value.
pop()	Removes an element by index and returns it.
reverse()	Reverses the original list.
sort()	Sorts the original list.
sorted()	Returns a new sorted list.
min()	Returns the smallest element.
max()	Returns the largest element.
sum()	Returns the total of all numeric elements.

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Real-Life Applications

• Finding the highest and lowest marks of students.
• Calculating total sales.
• Sorting examination results.
• Maintaining ranking lists.
• Removing cancelled orders from a list.
• Displaying records in alphabetical order.

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Common Programming Mistakes

• Confusing sort() with sorted().
• Using remove() for an element that does not exist.
• Calling pop() with an invalid index.
• Applying sum() to a list containing strings.
• Expecting sort() to return a new list.

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CBSE Important Programs

1. Remove an element from a list.
2. Remove the last element using pop().
3. Reverse a list.
4. Sort a list in ascending order.
5. Sort a list in descending order.
6. Find the minimum value.
7. Find the maximum value.
8. Calculate the sum of list elements.
9. Display the removed element using pop().
10. Create a sorted copy of a list using sorted().

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Viva Questions

1. What is the difference between remove() and pop()?
2. Which method removes an element by value?
3. Which method removes an element by index?
4. Differentiate between sort() and sorted().
5. Which function returns the smallest element?
6. Which function returns the largest element?
7. What is the purpose of the sum() function?
8. Can sort() arrange elements in descending order?
9. What happens if remove() cannot find the specified value?
10. What happens if pop() is used with an invalid index?

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Exam Tips

• Use remove() to delete by value.
• Use pop() to delete by index.
• Remember that sort() modifies the original list.
• Use sorted() when the original list must remain unchanged.
• min(), max(), and sum() work with numeric lists.

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