Proctor level_134

Simplemodels.py har table ki class hai — columns, PK/FK, relationships. Yeh Model layer hai.

Viva mein file khol ke bolo:
1) Kaunsi classes/tables hain (User, Role-specific, Booking...)
2) Har table ka kaam 1 line
3) Relationships: 1-1 / 1-M / M-M, backref, cascade, lazy
4) Constraints: unique email, nullable, default status

Example skeleton

class User(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    email = db.Column(db.String(120), unique=True, nullable=False)
    role = db.Column(db.String(20), default='user')
    bookings = db.relationship('Booking', backref='user', cascade='all, delete-orphan')

ER diagram: rectangles entities, lines relationships, PK/FK mark. Schema = yahi structure.
Tables create: db.create_all() ya migrations. SQLite file SQL viewer se dikha sakte ho.

SimpleRoutes/controllers URLs handle karte hain. app.py app banata hai, models.py data, templates/ views, static/ CSS-JS.

Typical structure:
app.py / __init__.py → Flask app, db.init, register blueprints
models.py → tables
routes.py / views → @app.route functions
templates/ → Jinja HTML
static/ → css, images
instance/*.db → SQLite

Ek route explain karne ka template:
1) URL + methods 2) Auth/role check 3) Form/query se data 4) Business rule (duplicate, slots) 5) db.session 6) render ya redirect

Example GET+POST same route: GET form, POST save.
Data HTML se: form name= → request.form. Data HTML ko: render_template(..., items=query).
Nayi .py file: import karke use karo, warna Flask ko pata nahi. Folder rename: imports/paths/templates check.

SimpleDemo script pehle se practice karo, 5-7 minute, saari roles.

Suggested flow

1) Register/login user 2) Admin login — CRUD 3) Approval/blacklist 4) Booking/apply 5) Search 6) Validation edge (slots 0, duplicate) 7) Logout
Bolte-bolte dikhao: 'Yahan overbooking rokta hoon'. Code tab kholna jab poochhein.
Crash ho to debug calmly: terminal error, typo, DB path.
Mandatory features skip mat karna — examiner list tick karta hai.

SimplePrimary Key row ki unique ID hai, Foreign Key doosri table ki Primary Key ko point karti hai.

Primary Key: unique + not null. Har table mein hota hai. Example: user.id = 5
Foreign Key: relationship banati hai. post.user_id = 5 matlab yeh post user 5 ki hai.

Example

class User(db.Model):
    id = db.Column(db.Integer, primary_key=True)
class Post(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    user_id = db.Column(db.Integer, db.ForeignKey('user.id'))

FK Primary Key bhi ho sakti hai (1-to-1 profile table). FK unique ho to One-to-One, nahi to One-to-Many.

Simplebackref relationship ki reverse side automatically bana deta hai.

class Post(db.Model):
    user_id = db.Column(db.Integer, db.ForeignKey('user.id'))
    user = db.relationship('User', backref='posts')

Ab post.user milta hai, aur user.posts bhi — Post model pe sirf ek line.
secondary Many-to-Many junction table ke liye: relationship(..., secondary=likes_table, backref='liked_by').
Explicit chahiye to back_populates use karo.

SimpleORM = Object Relational Mapping. Database tables ko Python classes/objects se map karta hai, raw SQL kam likhni padti hai.

Bina ORM: cursor.execute('SELECT * FROM user WHERE id=?', [5])
ORM se: User.query.get(5) ya db.session.get(User, 5)

Example model

class User(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    email = db.Column(db.String(120), unique=True)

FaydePython mein soch sakte ho, SQL injection se protection (parameterized), relationships easy, DB switch thoda aasan.

Nuksaancomplex queries slow/abstract, seekhne ki layer extra, kabhi raw SQL phir bhi chahiye.

MAD1: SQLAlchemy (Flask-SQLAlchemy). Tables db.create_all() ya migrations se banti hain.

Simplerender_template HTML file ko Jinja se process karke browser ko bhejta hai. Backend data ko frontend se jodta hai.

return render_template('dashboard.html', user=user, treks=treks)

File templates/dashboard.html honi chahiye.
Keyword arguments template mein variables ban jaate hain: {{ user.name }}.
Route kuch return na kare to Flask error. Boolean return typical HTML view ke liye nahi — string/Response chahiye.

SimpleGET data mangta hai (read), POST data bhejta hai (create/submit).

GETURL mein dikhta hai, bookmark ho sakta hai, browser back/refresh safe hai, data URL query mein jaata hai. Search, page open, login form dikhana.

POSTbody mein data jaata hai, URL mein password nahi dikhta, refresh pe dubara submit ho sakta hai. Login, register, form save.

Example

# page dikhana

@app.route('/login', methods=['GET', 'POST'])
def login():
    if request.method == 'GET':
        return render_template('login.html')
    # POST: form submit
    email = request.form.get('email')
    ...

GET se theoretically data bhej sakte ho (?q=flask), lekin create/update ke liye nahi use karna — data log/history mein save ho jaata hai, length limit hoti hai.
HTML form default GET hota hai; method='POST' likhna zaroori hai login/register pe.

SimpleDOM = Document Object Model — HTML ka tree jo browser memory mein banata hai. JS isi ko change karta hai.

document.getElementById('btn').style.color = 'red'
Jinja server pe HTML banata hai, phir browser DOM parse karta hai. Vue DOM ko reactive update karta hai.