Low-Level Design (LLD) of a Polling System 🗳️
A Polling System allows users to create, vote on, and view polls. This design covers essential components, class structure, and workflow.

Step 1: Identify the Core Functionalities
🔹 User Management → Users can create polls & vote.
🔹 Poll Management → Create, edit, and delete polls.
🔹 Voting Mechanism → Users can vote once per poll.
🔹 Result Computation → Count votes and display results.

Step 2: Identify the Key Entities & Relationships
User → Represents the users participating in polls.
Poll → Stores details about a specific poll.
Option → Represents the choices in a poll.
Vote → Tracks the votes cast by users.
Step 3: Define the Class Structure
1. User Class
python
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class User:
    def __init__(self, user_id: int, name: str):
        self.user_id = user_id
        self.name = name

    def get_details(self):
        return f"User: {self.name} (ID: {self.user_id})"
✔ Stores basic user information.

2. Poll Class
python
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class Poll:
    def __init__(self, poll_id: int, creator: User, question: str, options: list):
        self.poll_id = poll_id
        self.creator = creator
        self.question = question
        self.options = {option: 0 for option in options}  # Stores votes for each option
        self.voters = set()  # Track users who voted
        self.is_active = True  # Poll status

    def vote(self, user: User, option: str):
        if not self.is_active:
            return "Poll is closed."
        if user.user_id in self.voters:
            return "User has already voted."
        if option not in self.options:
            return "Invalid option."

        self.options[option] += 1
        self.voters.add(user.user_id)
        return f"{user.name} voted for '{option}'"

    def close_poll(self):
        self.is_active = False
        return "Poll closed."

    def get_results(self):
        return self.options if not self.is_active else "Poll is still active."
✔ Handles poll creation, voting, and results computation.

3. PollManager Class
python
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class PollManager:
    def __init__(self):
        self.polls = {}  # {poll_id: Poll object}
        self.poll_counter = 1

    def create_poll(self, creator: User, question: str, options: list):
        if len(options) < 2:
            return "A poll must have at least two options."

        poll = Poll(self.poll_counter, creator, question, options)
        self.polls[self.poll_counter] = poll
        self.poll_counter += 1

        return f"Poll '{question}' created with ID {poll.poll_id}"

    def get_poll(self, poll_id: int):
        return self.polls.get(poll_id, "Poll not found.")

    def close_poll(self, poll_id: int):
        if poll_id not in self.polls:
            return "Poll not found."

        return self.polls[poll_id].close_poll()
✔ Manages poll creation, retrieval, and closing polls.

Step 4: Testing the System
python
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# Initialize Poll Manager
poll_mgr = PollManager()

# Create Users
user1 = User(1, "Alice")
user2 = User(2, "Bob")
user3 = User(3, "Charlie")

# Create a Poll
print(poll_mgr.create_poll(user1, "Best Programming Language?", ["Python", "Java", "C++"]))

# Fetch Poll
poll = poll_mgr.get_poll(1)
if isinstance(poll, Poll):
    print(poll.vote(user1, "Python"))  # Alice votes for Python
    print(poll.vote(user2, "Java"))    # Bob votes for Java
    print(poll.vote(user3, "Python"))  # Charlie votes for Python

    print(poll.get_results())  # Display poll results

    print(poll_mgr.close_poll(1))  # Close poll

    print(poll.get_results())  # Display final results
Step 5: Explanation
User Class → Represents users who create & vote on polls.
Poll Class → Manages poll data, voting logic, and results.
PollManager → Handles poll creation, retrieval, and management.
Step 6: Enhancements & Scalability
🔹 Multiple-choice Voting → Allow users to select multiple options.
🔹 Poll Expiry → Auto-close polls after a set duration.
🔹 Anonymous Polls → Hide voter identities.
🔹 Real-time Updates → Use WebSockets for live results.
🔹 Database Integration → Store polls & votes persistently.

🚀 Conclusion
This LLD provides a modular, scalable, and extendable Polling System. Users can create, vote, and view poll results seamlessly! 🗳️