Question

Describe the following list methods: a. index b. insert c. sort d. reverse

Short answer

Question: Provide a brief explanation and example of the following Python list methods: index, insert, sort, and reverse. Answer: The `index()` method finds the first occurrence of a specified element in a list and returns its index. For example, if we have a list `numbers = [1, 2, 3, 4, 3, 5]`, calling `numbers.index(3)` would return 2. The `insert()` method inserts a new element in a list at a specified index. For instance, if we have a list `fruits = ['apple', 'banana', 'cherry']`, calling `fruits.insert(1, 'orange')` would result in `['apple', 'orange', 'banana', 'cherry']`. The `sort()` method sorts a list in ascending order by default but can also be sorted in descending order using the `reverse` parameter. For example, a list `numbers = [3, 1, 5, 2, 4]` would become `[1, 2, 3, 4, 5]` after calling `numbers.sort()`, and `[5, 4, 3, 2, 1]` after calling `numbers.sort(reverse=True)`. The `reverse()` method reverses the order of elements in a list. For instance, a list `colors = ['red', 'green', 'blue', 'yellow']` would become `['yellow', 'blue', 'green', 'red']` after calling `colors.reverse()`.

Step-by-step solution

a. index method

The `index()` method is used to find the first occurrence of a specified element in a list. It takes the element as its argument and returns the index of the first occurrence of the element. If the element is not found in the list, it raises a ValueError. Example: ``` numbers = [1, 2, 3, 4, 3, 5] # Find the first occurrence of 3 and get its index index_of_3 = numbers.index(3) print(index_of_3) # Output: 2 ```

b. insert method

The `insert()` method is used to insert a new element in a list at a specified index. It takes two arguments - the index position where the new element should be added, and the new element itself. Example: ``` fruits = ['apple', 'banana', 'cherry'] # Insert a new element 'orange' at index 1 fruits.insert(1, 'orange') print(fruits) # Output: ['apple', 'orange', 'banana', 'cherry'] ```

c. sort method

The `sort()` method is used to sort a list in ascending order, by default. It modifies the original list and doesn't return any value. You can also sort the list in descending order by setting the `reverse` parameter to `True`. Example: ``` numbers = [3, 1, 5, 2, 4] # Sort the list in ascending order numbers.sort() print(numbers) # Output: [1, 2, 3, 4, 5] # Sort the list in descending order numbers.sort(reverse=True) print(numbers) # Output: [5, 4, 3, 2, 1] ```

d. reverse method

The `reverse()` method is used to reverse the order of elements in a list. It modifies the original list and doesn't return any value. Example: ``` colors = ['red', 'green', 'blue', 'yellow'] # Reverse the order of elements in the list colors.reverse() print(colors) # Output: ['yellow', 'blue', 'green', 'red']