Language

Dictionaries

Source: 3-Data Structures/3.4-Dictionaries.ipynb

Start here — no coding background needed

What you will learn

Look up values by a name (key) — like a phone contact book.

In simple words

Dictionary `{key: value}` — find phone by name, price by product code.

Think of it like this

Contacts app: name → phone number.

Words to know:

dict — Key → value pairs in curly braces
key — The label you look up

Ways to store many values together — shopping lists, contacts, unique items.

Easy example — try this first

Easy example — run this first. Change values and press Run again.

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Reference notes (from full bootcamp)

Optional — deeper detail for when you are ready

Dictionaries

Video Outline:

Introduction to Dictionaries
Creating Dictionaries
Accessing Dictionary Elements
Modifying Dictionary Elements
Dictionary Methods
Iterating Over Dictionaries
Nested Dictionaries
Dictionary Comprehensions
Practical Examples and Common Errors

Introduction to Dictionaries

Dictionaries are unordered collections of items. They store data in key-value pairs.

Keys must be unique and immutable (e.g., strings, numbers, or tuples), while values can be of any type.

Reference example

Output

Expected (from notebook):
<class 'dict'>

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Reference example

Output

Expected (from notebook):
{}

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Reference example

Output

Expected (from notebook):
{'name': 'Anshul', 'age': 32, 'grade': 24}
<class 'dict'>

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Reference example

Output

Expected (from notebook):
{'name': 24, 'age': 32}

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Reference example

Output

Expected (from notebook):
{'name': 'Anshul', 'age': 32, 'grade': 'A'}

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Reference example

Output

Expected (from notebook):
A
32
A
None
Not Available

Runs in your browser via Pyodide — no server. First run may take a few seconds.

Reference example

Output

Expected (from notebook):
{'name': 'Anshul', 'age': 32, 'grade': 'A'}

Runs in your browser via Pyodide — no server. First run may take a few seconds.

Reference example

Output

Expected (from notebook):
{'name': 'Anshul', 'age': 33, 'grade': 'A'}
{'name': 'Anshul', 'age': 33, 'grade': 'A', 'address': 'India'}

Runs in your browser via Pyodide — no server. First run may take a few seconds.

Reference example

Output

Expected (from notebook):
{'name': 'Anshul', 'age': 33, 'address': 'India'}

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Reference example

Output

Expected (from notebook):
dict_keys(['name', 'age', 'address'])
dict_values(['Anshul', 33, 'India'])
dict_items([('name', 'Anshul'), ('age', 33), ('address', 'India')])

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Reference example

Output

Expected (from notebook):
{'name': 'Anshul1', 'age': 33, 'address': 'India'}
{'name': 'Anshul1', 'age': 33, 'address': 'India'}

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Reference example

Output

Expected (from notebook):
{'name': 'Anshul2', 'age': 33, 'address': 'India'}
{'name': 'Anshul2', 'age': 33, 'address': 'India'}

Runs in your browser via Pyodide — no server. First run may take a few seconds.

Reference example

Output

Expected (from notebook):
{'name': 'Anshul2', 'age': 33, 'address': 'India'}
{'name': 'Anshul2', 'age': 33, 'address': 'India'}

Runs in your browser via Pyodide — no server. First run may take a few seconds.

Reference example

Output

Expected (from notebook):
{'name': 'Anshul2', 'age': 33, 'address': 'India'}
{'name': 'Anshul3', 'age': 33, 'address': 'India'}

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Reference example

Output

Expected (from notebook):
name
age
address

Runs in your browser via Pyodide — no server. First run may take a few seconds.

Reference example

Output

Expected (from notebook):
Anshul3
33
India

Runs in your browser via Pyodide — no server. First run may take a few seconds.

Reference example

Output

Expected (from notebook):
name:Anshul3
age:33
address:India

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Reference example

Output

Expected (from notebook):
{'student1': {'name': 'Anshul', 'age': 32}, 'student2': {'name': 'Peter', 'age': 35}}

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Reference example

Output

Expected (from notebook):
Peter
35

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Reference example

Output

Expected (from notebook):
dict_items([('student1', {'name': 'Anshul', 'age': 32}), ('student2', {'name': 'Peter', 'age': 35})])

Runs in your browser via Pyodide — no server. First run may take a few seconds.

Reference example

Output

Expected (from notebook):
student1:{'name': 'Anshul', 'age': 32}
name:Anshul
age:32
student2:{'name': 'Peter', 'age': 35}
name:Peter
age:35

Runs in your browser via Pyodide — no server. First run may take a few seconds.

Reference example

Output

Expected (from notebook):
{0: 0, 1: 1, 2: 4, 3: 9, 4: 16}

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Reference example

Output

Expected (from notebook):
{0: 0, 2: 4, 4: 16, 6: 36, 8: 64}

Runs in your browser via Pyodide — no server. First run may take a few seconds.

Reference example

Output

Expected (from notebook):
{1: 1, 2: 2, 3: 3, 4: 4}

Runs in your browser via Pyodide — no server. First run may take a few seconds.

Reference example

Output

Expected (from notebook):
{'a': 1, 'b': 3, 'c': 4}

Runs in your browser via Pyodide — no server. First run may take a few seconds.

Conclusion

Dictionaries are powerful tools in Python for managing key-value pairs. They are used in a variety of real-world scenarios, such as counting word frequency, grouping data, storing configuration settings, managing phonebooks, tracking inventory, and caching results. Understanding how to leverage dictionaries effectively can greatly enhance the efficiency and readability of your code.

Practice test — try yourself

Write code, press Check. Wrong answer shows the correct code to copy & run.

student = {"name":"Anshul","city":"Dehradun"}. Print the city.