Unit III: Data Structures and Modules

Table of Contents

1. Lists
2. Tuples
3. Sets
4. Dictionaries
5. Python Modules
6. String Manipulation

1. Lists

A List is an ordered, mutable collection of items that can be of different data types.

Indexing: Lists use zero-based indexing to access elements.
Operations: Supports concatenation (joining lists), repetition (multiplying elements), membership (checking if item exists), and slicing (extracting parts of a list).
Traversal: Lists can be traversed using loops to process each element sequentially.
Nested Lists: Lists can contain other lists as elements.
Built-in Methods: Python provides various methods to manipulate lists, such as append(), extend(), and insert().

2. Tuples

A Tuple is an ordered, immutable sequence of items. Once created, its elements cannot be changed.

Indexing: Similar to lists, tuples use indexing to access specific items.
Operations: Supports concatenation, repetition, membership, and slicing.
Built-in Functions: Common functions include len(), max(), and min().

3. Sets

A Set is an unordered collection of unique elements.

Creation: Sets are created using curly braces {} or the set() function.
Modification: Elements can be added or removed, but sets do not support indexing or slicing because they are unordered.
Operations: Includes mathematical set operations like union, intersection, difference, and symmetric difference.
Methods: Common methods include add(), remove(), and pop().

4. Dictionaries

A Dictionary is a mapping of unique keys to values.

Accessing Items: Values are accessed using their associated keys rather than index numbers.
Mutability: Dictionaries are mutable, allowing for adding new terms or modifying existing items.
Traversal: You can traverse a dictionary to access keys, values, or key-value pairs using loops.
Built-in Methods: Includes keys(), values(), and items().

5. Python Modules

A Module is a file containing Python definitions and statements that can be reused in other programs.

Importing: Modules are imported using the import <module> statement or the from ... import ... syntax.
Math Module: A built-in module providing access to mathematical functions like sqrt(), sin(), and cos().

6. String Manipulation

Advanced string handling techniques are vital for data processing.

Basic Operations: Includes string concatenation and repetition.
Slicing: Using range indices to extract substrings.

Exam Tips: Data Structure Comparison

Structure	Ordered?	Mutable?	Duplicates?
List	Yes	Yes	Allowed
Tuple	Yes	No	Allowed
Set	No	Yes	No
Dictionary	No (pre-3.7)	Yes	Keys must be unique

Common Mistakes

Trying to change a tuple element (Tuples are immutable!).
Using a mutable type (like a list) as a dictionary key.
Assuming sets maintain the order in which items were added.

Frequently Asked Questions

Q1: When should I use a Tuple instead of a List?
Use a tuple when you have data that should not change throughout the program (e.g., coordinates, constant settings) to ensure data integrity.

Q2: How do I remove duplicates from a list?
The easiest way is to convert the list to a set using set(my_list) and then back to a list, as sets automatically handle unique elements.