Mutable vs Immutable Types

Data Structures in Python

This note covers the fundamental data structures in Python. I’ll need to expand on several of these in separate notes.

1. Built-in Data Structures:

Python offers several built-in data structures:

• Lists: Ordered, mutable (changeable) sequences of items. Allow duplicate elements.

my_list = 1, 2, "hello", 3.14, True]]

• Tuples: Ordered, immutable (unchangeable) sequences of items. Allow duplicate elements. Useful for representing fixed collections of data.

my_tuple = (1, 2, "hello", 3.14, True)

• Sets: Unordered collections of unique items. Useful for membership testing and eliminating duplicates.

my_set = {1, 2, 3, 3, 4} # {1, 2, 3, 4}

• Dictionaries: Unordered collections of key-value pairs. Keys must be immutable (e.g., strings, numbers, tuples), values can be any data type. Provides efficient lookups by key.

my_dict = {"name": "Alice", "age": 30, "city": "[New York](./../new-york/)"}

2. Data Structure Operations:

Each data structure has its own set of operations (methods):

• Lists: append(), insert(), remove(), pop(), sort(), reverse(), index(), count() etc. (List Methods)
• Tuples: Limited operations due to immutability. index(), count(). (Tuple Methods)
• Sets: add(), remove(), union(), intersection(), difference() etc. (Set Methods)
• Dictionaries: get(), items(), keys(), values(), update(), pop(), popitem() etc. (Dictionary Methods)

3. Choosing the Right Data Structure:

The choice of data structure depends on the specific needs of your program:

• Use lists when you need an ordered, mutable sequence.
• Use tuples when you need an ordered, immutable sequence.
• Use sets when you need to store unique items and perform set operations.
• Use dictionaries when you need to store data in key-value pairs for efficient lookups.

4. More Advanced Data Structures (Advanced Data Structures)

This section will cover more advanced data structures, like:

• Deque (double-ended queue): Efficient for adding and removing elements from both ends.
• Namedtuple: Similar to tuples, but with named fields for better readability.
• Counter: A dictionary subclass for counting hashable objects.
• OrderedDict (deprecated in Python 3.7+): Maintained order of insertion. (Use collections.OrderedDict if needed for older Python versions).

5. Further Reading:

• Python documentation on built-in types.
• Relevant chapters in a Python textbook.

Linked Notes: List Methods, Tuple Methods, Set Methods, Dictionary Methods, Advanced Data Structures