Python Learning Session-10 : Dictionaries in Python –from lists, tuples and Key-Value Power!.

 

Session-10 : Dictionaries in Python –from lists, tuples and Key-Value Power!.

✅ Learning Objectives

• Understand what sets are in Python.
• Learn how sets differ from lists and tuples.
• Explore set operations (union, intersection, difference, symmetric difference).
• Work with set methods like add(), remove(), discard(), update().
• Understand immutability with frozenset.

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📌 Key Concepts

1. Definition:
   A set is an unordered collection of unique elements in Python.
   Example:

Python

my_set = {1, 2, 3, 3} # Output: {1, 2, 3}

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2. Why Sets?
• Automatically removes duplicates.
• Faster membership testing (in operator).
• Useful for mathematical operations.
3. Creating Sets:

Python

s1 = {1, 2, 3}

s2 = set([4, 5, 6])

empty_set = set() # {} creates a dictionary, not a set

 

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4. Common Operations:

Python

a = {1, 2, 3}

b = {3, 4, 5}

 

print(a | b) # Union: {1, 2, 3, 4, 5}

print(a & b) # Intersection: {3}

print(a - b) # Difference: {1, 2}

print(a ^ b) # Symmetric Difference: {1, 2, 4, 5}

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5. Methods:
• add(), remove(), discard(), pop(), clear()
• update() for merging sets.
6. frozenset:
• Immutable version of a set.

Python

fs = frozenset([1, 2, 3])

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🛠 Practice Ideas

• Remove duplicates from a list using a set.
• Find common elements between two lists.
• Write a program to check if two sets are disjoint.
• Implement a simple set-based membership system.

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Key-Value Power

Learning Objectives

• Understand what dictionaries are and why they are useful.
• Learn how to create, access, and modify dictionary elements.
• Explore dictionary methods like get(), keys(), values(), items(), update().
• Understand nested dictionaries and dictionary comprehensions.

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📌 Key Concepts

1. Definition:
   A dictionary is an unordered collection of key-value pairs.
   Example:

Python

my_dict = {"name": "Hitesh", "role": "Engineer"}

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2. Creating Dictionaries:

Python

d1 = {"a": 1, "b": 2}

d2 = dict(x=10, y=20)

empty_dict = {}

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3. Accessing & Modifying:

Python

print(d1["a"]) # 1

print(d1.get("c")) # None

d1["b"] = 5 # Modify value

d1["c"] = 3 # Add new key-value

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4. Common Methods:
• keys(), values(), items()
• update(), pop(), clear()
5. Dictionary Comprehension:

Python

squares = {x: x**2 for x in range(5)}

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6. Nested Dictionaries:

Python

student = {

"name": "Hitesh",

"marks": {"math": 90, "science": 85}

 

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🛠 Practice Ideas

• Count word frequency in a sentence using a dictionary.
• Merge two dictionaries.
• Create a dictionary from two lists (keys and values).
• Implement a simple phonebook using a dictionary.