Creating Lists
A list in Python can be created by placing a sequence of values (items) separated by commas within square brackets:
```python
my_list = [1, 2, 3, 4, 5]
```
Lists can contain items of different data types, although it is typical for all items to be of the same type:
```python
mixed_list = [1, "two", 3.0, True]
```
Indexing and Slicing
Like strings and other built-in sequence types, lists can be indexed and sliced. Indexing refers to accessing an element of the list by its position, starting with 0 for the first element:
```python
first_element = my_list[0] # Returns 1
```
Slicing allows you to obtain a sublist by specifying a start and end index (end index not included):
```python
sublist = my_list[1:3] # Returns [2, 3]
```
All slice operations return a new list containing the requested elements, which means that the following slice returns a shallow copy of the list:
```python
copy_of_list = my_list[:]
```
List Operations
Lists support a variety of operations, such as concatenation using the `+` operator:
```python
list1 = [1, 2, 3]
list2 = [4, 5, 6]
combined_list = list1 + list2 # Returns [1, 2, 3, 4, 5, 6]
```
Unlike strings, which are immutable, lists are mutable. This means you can change their content. For example, you can modify an element of the list directly:
```python
my_list[2] = "three"
```
Adding and Removing Elements
You can add new items to the end of the list using the `append()` method:
```python
my_list.append(6) # my_list becomes [1, 2, "three", 4, 5, 6]
```
Assignment to slices is also possible, allowing changes in size of the list or even clearing it entirely:
```python
my_list[1:3] = ["a", "b", "c"] # my_list becomes [1, "a", "b", "c", 4, 5, 6]
my_list[:] = [] # Clears the list, making it empty
```
The built-in function `len()` can be used to get the number of items in a list:
```python
length = len(my_list) # Returns 7, if my_list was not cleared
```
Nested Lists
Lists can also be nested, meaning you can create lists that contain other lists:
```python
nested_list = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
```
You can access elements of the nested lists using multiple indices:
```python
element = nested_list[1][2] # Returns 6
```
