Python Tutorial 4.3 - Dictionaries in Python

Welcome to the “Dictionaries in Python” tutorial!

Overview

Dictionaries store key‑value pairs and are insertion‑ordered (Python 3.7+), mutable mappings.

Creating Dictionaries

student = {"name": "Alice", "age": 25, "major": "CS"}
empty = {}

Common Operations

• Accessing Values:

  print(student["name"])   # "Alice"
  

• Adding/Updating Items:

  student["gpa"] = 3.8
  student["age"] = 26
  

• Removing Items:

  student.pop("major")
  

• Keys, Values, and Items:

  student.keys()    # dict_keys(["name", "age", "gpa"])
  student.values()  # dict_values(["Alice", 26, 3.8])
  student.items()   # dict_items([("name","Alice"),...])
  

Iterating

for key, value in student.items():
    print(f"{key}: {value}")

Key Takeaways

• Use dictionaries when you need fast lookups by key.
• Methods like pop(), keys(), and items() are essential.
• Dictionary comprehensions can build dicts from iterables (advanced topic).

Happy coding!