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Dictionaries – Basics (creation, accessing)

A dictionary maps unique keys to values using key: value pairs inside curly braces

What it does: A dictionary stores data as key-value pairs inside curly braces: person = {'name': 'Alice'}. The key is the label used to look something up, and the value is the data stored under it. A value is accessed with square brackets around its key — person['name'] — which looks items up by name rather than by position, unlike a list.

Common mistakes: Using square brackets to create a dictionary — person = ['name': 'Alice'] — is a syntax error; dictionaries need curly braces {}. Looking up a key that doesn't exist raises a KeyError rather than returning nothing.

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Learning

Duo

What is a dictionary?

A collection of key-value pairsAn ordered list of items

Matches

❌ person = {'name': 'Ali'} print(person['age'])

↓

Error: Key 'age' doesn't exist

Applying

Meanings

Term

Dictionary

Meaning

A collection of key-value pairs in curly braces {}.

Practice

person = {'name': 'Alice', 'age': 15}

Testing

Gaps

person = 'name': 'Alice'

Check Answer

Spots

1# Create a person dictionary

2person = ['name': 'Alice']

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Quick Questions

1. What is a dictionary?

A. A collection of key-value pairs ✓

B. An ordered list of items

Dicts store data as pairs — each key maps to a value, like a lookup table

2. How do you create a dictionary?

A. Square brackets []

B. Curly braces {} ✓

Square brackets [] make lists; curly braces {} make dicts (or sets)

3. d = {'a': 1}\nprint(d['a'])\nWhat prints?

A. 1 ✓

B. 'a'

d['a'] looks up the key 'a' and returns its value, which is 1

4. What separates a key from its value?

A. An equals sign =

B. A colon : ✓

Syntax is key: value — e.g. {'name': 'Alice'}

5. Can dictionary keys be duplicated?

A. No each key must be unique ✓

B. Yes

If you assign the same key twice, the second value overwrites the first

Match the Pairs

person = {'name': 'Ali'} print(person['age']) → Error: Key 'age' doesn't exist

d = {name: 'Alice'} → Error: Keys need quotes if string

person = {'name': 'Ali', 'age': 20} → Valid: Dict with two key-value pairs

d = {} d['x'] = 10 → Ok: Add key to empty dict

p = {'name':'Ali'} print(p['name']) → Output: Ali

p = {} print(type(p)) → Output: <class 'dict'>

Key Term

Dictionary

A collection of key-value pairs in curly braces {}.~~Key

Fill in the Blanks

1. person = {'name': 'Alice'}

2. print(person['name'])

3. d = {} d['color'] = 'blue'

4. pet = {'type': 'cat'}

5. scores = {'math': 90, 'english': 85}

Spot the Error

Question 1

A # Create a person dictionary

B person = ['name': 'Alice']

C print('Name:', person['name'])

D print('Done')

Line B — Dictionaries use curly braces {}, not square brackets []

Question 2

A # Create a person dictionary

B person = {'name' = 'Alice'}

C print('Name:', person['name'])

D print('Done')

Line B — Use colon : between key and value, not equals =

Question 3

A person = {'name': 'Alice'}

B greeting = person[name]

C print('Hello,', greeting)

D print('Done')

Line B — Key must be in quotes: 'name' is a string, not a variable

Question 4

A person = {'name': 'Alice'}

B greeting = person('name')

C print('Hello,', greeting)

D print('Done')

Line B — Use square brackets [] to access keys, not parentheses ()

Question 5

A person = {'name': 'Alice'}

B label = 'Greeting'

C greeting = person.name

D print('Hello,', greeting)

Line C — Use bracket notation person['name'], not dot notation person.name

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