Summary  
This chapter explains how to declare and initialize Python lists—ordered, mutable collections that can hold mixed data types—using literal notation for both populated and empty lists.

General domain of usage  
Data organization

Data structures are essential tools for organizing data, allowing for more efficient access depending on the specific needs of a program. They form the foundation of any programming language and are central to building functional and effective programs. In Python, the main data structures include **lists**, **tuples**, **dictionaries**, and **sets**, each offering unique features and capabilities.

### Understanding Python Lists
Python lists are **ordered collections** that are **mutable** and may contain elements of any data type. In Python, a list is created by putting the items inside square brackets. Here's an example:

# City name, population, area, is a major metropolitan
city_info = ["New York", 8419600, 468.9, True]

print(city_info)

As shown, a list can contain a mix of different items or even be completely empty. Take a look at the following example:

```python
cities = []
```

To initialize an empty list, simply assign empty square brackets to a variable.

import unittest
import importlib

def _dynamic_test(test_case, condition, success_message, failure_message):
    if condition:
        test_case._testMethodName = success_message
        test_case.assertTrue(True, success_message)
    else:
        test_case._testMethodName = failure_message
        test_case.fail(failure_message)

class TestUserCode(unittest.TestCase):

    def test_travel_wishlist_is_declared(self):
        import user_code
        _dynamic_test(
            self,
            hasattr(user_code, 'travel_wishlist'),
            "The `travel_wishlist` list is declared.",
            "Expected `travel_wishlist` to be declared."
        )

    def test_travel_wishlist_is_list(self):
        import user_code
        _dynamic_test(
            self,
            isinstance(user_code.travel_wishlist, list),
            "The `travel_wishlist` is of type `list`.",
            "Expected `travel_wishlist` to be of type `list`."
        )

    def test_travel_wishlist_correct_elements(self):
        import user_code
        expected_cities = {"London", "Tokyo", "Berlin"}
        actual_cities = set(user_code.travel_wishlist)
        _dynamic_test(
            self,
            actual_cities == expected_cities,
            "The `travel_wishlist` list contains the correct cities.",
            f"Expected `travel_wishlist` to contain {expected_cities}, but got {actual_cities}."
        )

    def test_travel_wishlist_has_exactly_three_elements(self):
        import user_code
        _dynamic_test(
            self,
            len(user_code.travel_wishlist) == 3,
            "The `travel_wishlist` list contains exactly 3 elements.",
            f"Expected `travel_wishlist` to have 3 elements, but got {len(user_code.travel_wishlist)}."
        )

if __name__ == '__main__':
    unittest.main()

test_main.py

Explore the fundamental data structures of the Python programming language, including lists, dictionaries, tuples, and sets, and learn how to apply them effectively to solve real-world programming challenges.

What is a list? A list is an ordered collection that can be modified. It also allows for duplicate elements.

Declaring and Initializing Lists in Python

Understanding Python Lists

解答