list Method

append()

Append is a predefined function. The append() function is used to add a new element to the end of an existing list.

The syntax for the append() function is listobj. append(Value), where Value is the element to be added.

# Creating a list lst = [10, 20, -30, 40] # Printing the original list print("Original list:", lst) # Output: Original list: [10, 20, -30, 40] # Appending elements using append() lst.append(50) # Adding integer 50 to the end lst.append("Python") # Adding string "Python" to the end # Printing updated list print("List after appending:", lst) # Output: List after appending: [10, 20, -30, 40, 50, 'Python'] # Appending a mixed-type element lst.append(3.14) # Adding float 3.14 to the end # Printing final list print("Final list:", lst) # Output: Final list: [10, 20, -30, 40, 50, 'Python', 3.14]

insert():

Insert is a predefined function. The insert() function is used to add an element at a specified position or index in a list.

The syntax for the insert() function is listobj.insert(Index, Value), where Index is the position and Value is the element to be added.

# Creating a list with variable name 'lst' lst = [10, 20, -30, 40] # Printing original list print("Original list:", lst) # Output: Original list: [10, 20, -30, 40] # Inserting elements using insert() lst.insert(1, 15) # Adding integer 15 at index 1 lst.insert(0, "Start") # Adding string "Start" at index 0 # Printing updated list print("List after inserting:", lst) # Output: List after inserting: ['Start', 10, 15, 20, -30, 40] # Inserting a mixed-type element lst.insert(3, 3.14) # Adding float 3.14 at index 3 # Printing final list print("Final list:", lst) # Output: Final list: ['Start', 10, 15, 3.14, 20, -30, 40]

Extend():

The extend() function is a predefined function used to add multiple elements at the end of a list.

The syntax for the extend() function is listobj. extend(list), where Index is the s the element to be added.

# Creating a list with variable name 'lst' lst = [10, 20, -30, 40] # Printing original list print("Original list:", lst) # Output: Original list: [10, 20, -30, 40] # Extending the list with another list lst.extend([50, 60]) # Adding elements [50, 60] at the end print("List after extending with [50, 60]:", lst) # Output: List after extending with [50, 60]: [10, 20, -30, 40, 50, 60] # Extending the list with a tuple lst.extend((3.14, "Python")) # Adding elements 3.14 and "Python" at the end print("List after extending with (3.14, 'Python'):", lst) # Output: List after extending with (3.14, 'Python'): [10, 20, -30, 40, 50, 60, 3.14, 'Python'] # Extending the list with a string (treated as iterable of characters) lst.extend("ABC") # Adding characters 'A', 'B', 'C' at the end print("List after extending with 'ABC':", lst) # Output: List after extending with 'ABC': [10, 20, -30, 40, 50, 60, 3.14, 'Python', 'A', 'B', 'C']

Remove():

The remove() function is used to delete the first occurrence of a specified element from a list based on its value.

The syntax is listobj. remove(Value), where Value is the element to be removed.

# Creating a list with variable name 'lst' lst = [10, 20, -30, 20, 40, "Python"] # Printing original list print("Original list:", lst) # Output: Original list: [10, 20, -30, 20, 40, 'Python'] # Removing the first occurrence of an element lst.remove(20) # Removes the first occurrence of 20 print("List after removing 20:", lst) # Output: List after removing 20: [10, -30, 20, 40, 'Python'] # Removing another element lst.remove("Python") # Removes the first occurrence of "Python" print("List after removing 'Python':", lst) # Output: List after removing 'Python': [10,

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

# Creating a list with variable name 'lst' lst = [10, 20, -30, 20, 40, "Python"] # Printing original list print("Original list:", lst) # Output: Original list: [10, 20, -30, 20, 40, 'Python'] lst.remove(50) # 50 is not in the list, will raise ValueError

pop(index):

The pop() function is used to remove and return an element from a list at a specified valid index; if the index is invalid, it raises an IndexError.

The syntax is listobj.pop(index), where index is the position of the element to be removed.

# Creating a list with variable name 'lst' and mixed data types lst = [10, "Start", 3.14, True, -30, "Python"] # Printing original list print("Original list:", lst) # Output: Original list: [10, 'Start', 3.14, True, -30, 'Python'] # Popping an element at a specific index popped_item = lst.pop(1) # Removes and returns element at index 1 ('Start') print("List after popping index 1:", lst) # Output: List after popping index 1: [10, 3.14, True, -30, 'Python'] print("Popped item:", popped_item) # Output: Popped item: Start # Popping the last element (default behavior, no index specified) popped_item = lst.pop() # Removes and returns the last element ('Python') print("List after popping last element:", lst) # Output: List after popping last element: [10, 3.14, True, -30] print("Popped item:", popped_item) # Output: Popped item: Python

If no index is provided, it removes and returns the last element by default.

# Creating a list with variable name 'lst' and mixed data types lst = [10, "Start", 3.14, True, -30, "Python"] # Printing original list print("Original list:", lst) # Output: Original list: [10, 'Start', 3.14, True, -30, 'Python'] lst.pop(7) # Index 7 does not exist, will raise IndexError

pop():

The pop() function, when called without an index, is used to remove and return the last element of a list.

The syntax is listobj.pop(), which deletes the last element from the list.

# Creating a list with variable name 'lst' and mixed data types lst = [10, "Start", 3.14, True, -30] # Printing original list print("Original list:", lst) # Output: Original list: [10, 'Start', 3.14, True, -30] # Popping the last element popped_item = lst.pop() # Removes and returns the last element (-30) print("List after popping last element:", lst) # Output: List after popping last element: [10, 'Start', 3.14, True] print("Popped item:", popped_item) # Output: Popped item: -30 # Popping the last element again popped_item = lst.pop() # Removes and returns the last element (True) print("List after popping last element:", lst) # Output: List after popping last element: [10, 'Start', 3.14] print("Popped item:", popped_item) # Output: Popped item: True

If the list is empty, it raises an IndexError.

# Creating an empty list to demonstrate error case lst_empty = [] # Attempting to pop from an empty list lst_empty.pop() # Will raise IndexError since the list is empty

clear():

The clear function is used to remove all elements from a list, leaving it empty.

The syntax is listobj.clear(), which deletes all elements from the list without returning any value.

# Creating a list with variable name 'lst' and mixed data types lst = [10, "Start", 3.14, True, -30] # Printing the original list print("Original list:", lst) # Output: Original list: [10, 'Start', 3.14, True, -30] print("Length of original list:", len(lst)) # Output: Length of original list: 5 # Using clear() to remove all elements lst.clear() # Removes all elements, making the list empty print("List after clear():", lst) # Output: List after clear(): [] print("Length after clear():", len(lst)) # Output: Length after clear(): 0

del

The del statement is a general-purpose function used to remove elements from any mutable object (like a list) based on indexing or slicing, or to delete the entire object.

The del statement can target a single element (del listobj[index]), a range of elements (del listobj[start :end]), or the entire object (del listobj), modifying the mutable object in place or removing it from memory.

# Creating a list with variable name 'lst' and mixed data types lst = [10, "Start", 3.14, True, -30, "Python"] # Printing the original list print("Original list:", lst) # Output: Original list: [10, 'Start', 3.14, True, -30, 'Python'] print("Length of original list:", len(lst)) # Output: Length of original list: 6 # Using del to remove a single element by index del lst[1] # Removes element at index 1 ('Start') print("List after del lst[1]:", lst) # Output: List after del lst[1]: [10, 3.14, True, -30, 'Python'] print("Length after del:", len(lst))

# Creating a list with variable name 'lst' and mixed data types lst = [10, "Start", 3.14, True, -30, "Python"] # Printing the original list print("Original list:", lst) # Output: Original list: [10, 'Start', 3.14, True, -30, 'Python'] print("Length of original list:", len(lst)) # Output: Length of original list: 6 # Using del to remove a range of elements by slicing del lst[1:4] # Removes elements from index 1 to 3 (3.14, True, -30) print("List after del lst[1:4]:", lst) # Output: List after del lst[1:4]: [10, 'Python'] print("Length after del:", len(lst)) # Output: Length after del: 2

# Creating a list with variable name 'lst' and mixed data types lst = [10, "Start", 3.14, True, -30, "Python"] del lst # Deletes the entire list object print(last) # it shows error

lst = [1, 2, 3] del lst[10] # Index 10 does not exist, will raise IndexError

count():

This function is used to count the number of occurrences of a specified element in a list.

Syntax: listobj. count(value).

It returns the number of times the specified value appears in the list.

# Counting occurrences of a number in a list numbers = [1, 2, 3, 2, 4, 2, 5] count_of_twos = numbers.count(2) print(f"Number of 2s in the list: {count_of_twos}") # Output: Number of 2s in the list: 3

# Counting occurrences of a string in a list fruits = ["apple", "banana", "apple", "orange", "apple"] count_of_apples = fruits.count("apple") print(f"Number of 'apple' in the list: {count_of_apples}") # Output: Number of 'apple' in the list: 3 Counting an element not present in the list count_of_mango = fruits.count("mango") print(f"Number of 'mango' in the list: {count_of_mango}") # Output: Number of 'mango' in the list: 0

This function is used to find the index of the first occurrence of a specified element in a list.

If the specified element is not found in the list, it raises a ValueError.

Syntax: listobj.index(element)

# Finding the index of a float in a list prices = [19.99, 29.99, 15.50, 29.99, 45.00] index_of_price = prices.index(29.99) print(f"Index of 29.99: {index_of_price}") # Output: Index of 29.99: 1

# Finding the index of a character in a list of characters letters = ['a', 'b', 'c', 'a', 'd'] index_of_c = letters.index('c') print(f"Index of 'c': {index_of_c}") # Output: Index of 'c': 2

# Using index() with a mixed-type list mixed_list = [1, "hello", 3.14, "hello", True] index_of_false = mixed_list.index(False) # Output: Error: 'False' not found in the list

copy()

This function creates a shallow copy of a list, copying the contents of one list object into another list object.

The new list is a separate object, but nested objects (e.g., lists within the list) are not copied deeply.

Syntax: listobj2 = listobj1.copy()

# Copy method() lst = [1,2,3,4,5] lst1 = lst.copy() print(lst1)

reverse():

This function reverses the order of elements in a list (from back to front). It modifies the original list in place and does not return a new list.

Syntax: listobj.reverse()

lst = [10, "Rossum", 55.55, "Python", "Hyd"] print(lst) # Output: [10, 'Rossum', 55.55, 'Python', 'Hyd'] lst.reverse() print(lst) # Output: ['Hyd', 'Python', 55.55, 'Rossum', 10] lst.reverse() print(lst) # Output: [10, 'Rossum', 55.55, 'Python', 'Hyd']

sort():

This function sorts the elements of a list in ascending order by default. It modifies the original list in place and does not return a new list.

Syntax: listobj.sort() (sorts in ascending order)

lst = [30, 10, 50, 20, 40] print(lst) # Output: [30, 10, 50, 20, 40] lst.sort() print(lst) # Output: [10, 20, 30, 40, 50]

Syntax: listobj.sort(reverse=False | True)

reverse=False: Sorts the list in ascending order (same as listobj.sort()).

lst = [30, 10, 50, 20, 40] print(lst) # Output: [30, 10, 50, 20, 40] lst.sort(reverse=False) print(lst) # Output: [50, 40, 30, 20, 10]

reverse=True: Sorts the list in descending order.

lst = [30, 10, 50, 20, 40] print(lst) # Output: [30, 10, 50, 20, 40] lst.sort(reverse=True) print(lst) # Output: [50, 40, 30, 20, 10]

>>> lst=["kiwi","banana","guava","apple","sberry"] >>> print(lst)----------['kiwi', 'banana', 'guava', 'apple', 'sberry'] >>> lst.sort() >>> print(lst)---------['apple', 'banana', 'guava', 'kiwi', 'sberry'] >>> lst.reverse() >>> print(lst)----------['sberry', 'kiwi', 'guava', 'banana', 'apple']