Lecture Notes: Advanced Python Features

Introduction

• Topic: Hidden and powerful features in Python
• Objective: Understand five key Python features to appear more professional

1. Anonymous Variable

• Underscore (_): Used as a placeholder for variables whose values are not needed.
• Use Cases:
  • For Loop: Replace unused loop variable. for _ in range(10): print("Do this")
  • Unpacking Coordinates: Avoid declaring unused variables. x, _ = coordinate x, _, z = larger_coordinate
  • List Comprehension: Avoid declaring unused variables. second_elements = [b for _, b in list_of_pairs]
• Benefits: Prevents linting errors and improves code clarity.

2. Else Statement in Loops

• While/For Loops with Else: The else block executes only if the loop is not terminated by a break statement.
• Example: for item in items: if item == 'B': break else: print("Do something here")
  • Output: else block runs if 'B' is not found and loop completes.
• Use Case: Useful for determining loop exit status without using additional flags.

3. Walrus Operator

• Operator: := (introduced in Python 3.8).
• Function: Assigns a value while using it in an expression.
• Examples:
  • While Loop: while (data := next(generator)) != -1: process(data)
  • List Comprehension: results = [result for x in range(10) if (result := f(x)) > 3]
• Benefits: More readable and efficient code.

4. Argument and Parameter Unpacking

• Single Asterisk (*): Unpacks iterable objects (e.g., lists, tuples). def func(a, b, c, d): pass values = [1, 2, 3, 4] func(*values)
• Double Asterisk (**): Unpacks dictionaries for keyword arguments. def func(key, target): pass kwargs = {'key': 5, 'target': 10} func(**kwargs)
• Benefits: Clean and flexible code for handling multiple arguments.

5. Default Dictionary

• Library: collections module.
• Class: defaultdict
• Function: Automatically assigns a default value to non-existing keys.
• Example: from collections import defaultdict def default(): return 0 char_count = defaultdict(default) for char in string: char_count[char] += 1
• Benefits: Simplifies code by removing the need for manual checks for key existence.

Conclusion

• Summary: Discussed five advanced Python features for professional coding.
• Additional Resources: Mentioned a software development program for further learning.