Model-View-Controller and Unicode

Model-View-Controller (MVC) with Flask & Unicode Essentials

This post introduces the Model-View-Controller (MVC) pattern using Flask and demystifies Unicode encoding for modern software development.

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1. MVC Pattern in Flask

MVC divides an application into three components: - Model: Handles data and business logic. - View: Manages UI and presentation. - Controller: Processes user input and updates Model/View.

Example: Flask Counter App

Project Structure

counter_app/
├── app.py
├── models.py
├── templates/
│   ├── index.html
│   └── layout.html
└── static/
    └── style.css

Model (models.py)

class Counter:
    def __init__(self):
        self.value = 0
    def increment(self):
        self.value += 1
        return self.value
    def decrement(self):
        self.value -= 1
        return self.value
    def reset(self):
        self.value = 0
        return self.value
    def get_value(self):
        return self.value

View (templates/index.html)

{% extends "layout.html" %}
{% block content %}
<div class="counter-container">
    <h1>Flask Counter App</h1>
    <div class="counter-display">{{ count }}</div>
    <div class="counter-controls">
        <form method="post" action="{{ url_for('increment') }}">
            <button type="submit">Increment</button>
        </form>
        <form method="post" action="{{ url_for('decrement') }}">
            <button type="submit">Decrement</button>
        </form>
        <form method="post" action="{{ url_for('reset') }}">
            <button type="submit">Reset</button>
        </form>
    </div>
</div>
{% endblock %}

Controller (app.py)

from flask import Flask, render_template, redirect, url_for
from models import Counter

app = Flask(__name__)
counter = Counter()

@app.route('/')
def index():
    count = counter.get_value()
    return render_template('index.html', count=count)

@app.route('/increment', methods=['POST'])
def increment():
    counter.increment()
    return redirect(url_for('index'))

@app.route('/decrement', methods=['POST'])
def decrement():
    counter.decrement()
    return redirect(url_for('index'))

@app.route('/reset', methods=['POST'])
def reset():
    counter.reset()
    return redirect(url_for('index'))

if __name__ == '__main__':
    app.run(debug=True)

Summary:
- Model: Counter logic
- View: HTML templates
- Controller: Flask routes
This separation improves maintainability and scalability.

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2. Unicode: The Universal Character Set

What is Unicode?

Unicode assigns a unique number to every character, supporting all major writing systems. It solves compatibility issues from legacy encodings.

Unicode vs. ASCII

• ASCII: 7 bits, 128 characters (mainly English)
• Unicode: Supports all languages and symbols

UTF-8 vs. UTF-16

• UTF-8: 1–4 bytes/character, ASCII-compatible, web standard
• UTF-16: 2 or 4 bytes/character, used by Windows/Java/JS

Character	Description	Code Point	UTF-8	UTF-16
A	Latin A	U+0041	41	0041
é	e with acute	U+00E9	C3 A9	00E9
π	Greek pi	U+03C0	CF 80	03C0
€	Euro sign	U+20AC	E2 82 AC	20AC
你	Chinese (nǐ)	U+4F60	E4 BD A0	4F60
😊	Smiling face	U+1F60A	F0 9F 98 8A	D83D DE0A

Unicode in Python

Python 3 strings are Unicode by default:

hello_world = "Hello, World! 你好，世界! こんにちは! 안녕하세요!"
print(hello_world)
print("Euro symbol: \u20AC")
print("Snowman: \u2603")
print("Smiling face: \U0001F60A")
print(ord('A'))      # 65
print(ord('€'))      # 8364
print(ord('😊'))     # 128522
print(chr(65))       # A
print(chr(8364))     # €
print(chr(128522))   # 😊

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Key Takeaways

• MVC: Cleanly separates logic, UI, and control flow.
• Unicode: Enables global, multilingual software.
• Python: Unicode support is built-in and straightforward.

Understanding these concepts is essential for building robust, internationalized applications.