🐍 Python Dictionaries: Your Personal “Address Book” for Data

Imagine you carry a little notebook where, on each page, you jot a label (“Mum’s phone”) and the thing it points to (“080-123-4567”). That notebook is a perfect metaphor for a dictionary in Python:

dog = {'name': 'Roger'}

One glance at the label ('name') instantly tells Python exactly where to retrieve its companion value ('Roger'). Unlike lists, where you hunt by position (index 0, index 1…), dictionaries let you jump straight to the item you care about—no counting required.

1. Building a Dictionary 🔨

A dictionary is wrapped in curly braces, with each key → value pair set off by a colon:

dog = {
    'name': 'Roger',
    'age': 8
}

Keys must be immutable (strings, numbers, tuples).
Values can be anything (strings, lists, even other dictionaries).

2. Reading & Updating Entries 📖✍️

Read

dog['name']      # ➡ 'Roger'
dog.get('age')   # ➡ 8
dog.get('color', 'unknown')  # ➡ 'unknown' (safe default)

Update

dog['name'] = 'Syd'      # modifies the existing entry
dog['favorite food'] = 'Meat'   # adds a brand-new pair

3. Cleaning Out the Kennel 🧹

Remove by key & return it

dog.pop('name')   # returns 'Syd' and deletes the key

Remove the most recently added pair
```
dog.popitem()     # last-in, first-out
```
Delete silently
```
del dog['favorite food']
```

4. Peeking Inside 🔍

Think of these like special X-ray glasses for dictionaries:

Action	Tool	Example	Result
Check membership	`in`	`'age' in dog`	`True / False`
List keys	`keys()`	`list(dog.keys())`	`['age']`
List values	`values()`	`list(dog.values())`	`[8]`
List pairs	`items()`	`list(dog.items())`	`[('age', 8)]`
Count pairs	`len()`	`len(dog)`	`1`

Need a fresh copy you can experiment on?

spare_dog = dog.copy()

5. Why Dictionaries Matter 🚀

Speed: Direct key look-ups are lightning fast—ideal for large data sets.
Clarity: Keys act like self-documenting labels, making code easier to read.
Flexibility: Values can hold anything—numbers, lists, even other dictionaries—unlocking powerful nested structures.

6. Practice Time 📝

Simple Lookup Create a dictionary car with keys 'brand', 'model', and 'year'. Retrieve and print the model.
Default Safety Net Using the get() method, attempt to access the key 'color' in the car dictionary from Question 1, but return 'unknown' if it’s missing.
Delete & Count Given inventory = {'apples': 30, 'bananas': 12, 'oranges': 10}, remove 'bananas' and print how many items remain.
Last-In, First-Out Start with an empty dictionary. Add three key/value pairs of your choosing. Call popitem() once. What remains, and why?
Nested Challenge Build a student dictionary where each key is a student’s name and each value is another dictionary holding "math" and "english" scores. Write code to print the average score for each student.

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