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Hajipur, Bihar, 844101
Python
Introduction to Python
Python Basics
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Python Syntax
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Python Comments
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Python Variables
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Python Data Types
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Python Casting
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Python I/O
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Python Operators
Cotrol Structures
Data Structures
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Python Strings
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Python Lists
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Python Tuples
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Python Dictionaries
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Python Sets
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Python Arrays
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Python Bytes and Bytearray
Date and Time
Functions and Module
File Handling
Python OOP
Advanced Concepts
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Python Scope
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Python Modules
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Python JSON
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Python RegEx
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Python PIP
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Python Try...Except
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Python String Formatting
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Python User Input
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Python VirtualEnv
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Python Math
Python DSA
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Python DSA
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Lists and Arrays
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Python Stacks
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Python Queues
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Linked Lists
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Python Hash Tables
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Python Trees
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Python Binary Trees
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Binary Search Trees
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Python AVL Trees
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Python Graphs
Searching Algorithms
Sorting Algorithms
Python Hash Tables
A Hash Table is a data structure that stores data in key-value pairs. In Python, the built-in dict (dictionary) is the most common way to implement a hash table.
Hash tables use a hash function to map keys to a specific index where the value is stored.
🔹 Creating a Hash Table in Python
# Create a hash table (dictionary)
students = {
"101": "Alice",
"102": "Bob",
"103": "Charlie"
}
print(students["102"]) # Output: Bob
✅ Keys can be strings, numbers, or tuples
✅ Values can be of any data type
🔹 Adding Items
students["104"] = "David"
🔹 Updating Values
students["103"] = "Eve"
🔹 Deleting Items
del students["101"]
🔹 Looping Through a Hash Table
for key, value in students.items():
print(key, ":", value)
🔹 Useful Dictionary Methods
| Method | Description |
|---|---|
dict.get(key) |
Returns value for key (or None) |
dict.keys() |
Returns all keys |
dict.values() |
Returns all values |
dict.items() |
Returns all key-value pairs |
dict.pop(key) |
Removes item by key |
key in dict |
Checks if key exists |
🔹 Hashing Example (Behind the Scenes)
print(hash("apple")) # Outputs an integer (hash value)
Python internally uses this hash value to store keys efficiently.
🔹 Use Cases of Hash Tables
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Storing user profiles
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Phonebooks
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Caching
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Counting items (frequency maps)
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Lookup tables
Practice Questions
Q1. Write a Python program to create a dictionary of employee ID → name.
Q2. Write a Python program to add a new employee to the dictionary.
Q3. Write a Python program to update the name of an existing employee.
Q4. Write a Python program to delete an employee using del keyword.
Q5. Write a Python program to check if the key "105" exists in the dictionary.
Q6. Write a Python program to use a loop to print all keys and values in the dictionary.
Q7. Write a Python program to get the value for key "104" using .get().
Q8. Write a Python program to list all keys using the .keys() method.
Q9. Write a Python program to remove an item from the dictionary using .pop().
Q10. Write a Python program to count the number of items in the dictionary using len().
Python
Introduction to Python
Python Basics
-
Python Syntax
-
Python Comments
-
Python Variables
-
Python Data Types
-
Python Casting
-
Python I/O
-
Python Operators
Cotrol Structures
Data Structures
-
Python Strings
-
Python Lists
-
Python Tuples
-
Python Dictionaries
-
Python Sets
-
Python Arrays
-
Python Bytes and Bytearray
Date and Time
Functions and Module
File Handling
Python OOP
Advanced Concepts
-
Python Scope
-
Python Modules
-
Python JSON
-
Python RegEx
-
Python PIP
-
Python Try...Except
-
Python String Formatting
-
Python User Input
-
Python VirtualEnv
-
Python Math
Python DSA
-
Python DSA
-
Lists and Arrays
-
Python Stacks
-
Python Queues
-
Linked Lists
-
Python Hash Tables
-
Python Trees
-
Python Binary Trees
-
Binary Search Trees
-
Python AVL Trees
-
Python Graphs
Searching Algorithms
Sorting Algorithms
