Interactions Between Classes

Interactions Between Classes#

⏳ Loading Pyodide…

Classes talking = Complete business systems Customer → Order → Product → Payment = Enterprise

$190K+ architects design these relationships

🎯 Class Relationships = Enterprise Architecture#

Relationship

Code

Business Example

Scale

Composition

self.account = Account()

Customer HAS Account

1M+

Aggregation

self.orders = [Order()]

Customer HAS MANY Orders

10M+

Association

Order(customer)

Order KNOWS Customer

100M+

Dependency

Payment.process()

Payment USES Bank

Production

🚀 Step 1: Composition = “HAS-A” Relationship#

Output:

💳 Alice Johnson: +$2,500 (Balance: $2,500)
👤 COMPLETE CUSTOMER:
   Alice Johnson account balance: $2,500

🔥 Step 2: Aggregation = “HAS MANY” Orders#

🧠 Step 3: Association = Classes KNOW Each Other#

📊 Step 4: FULL ENTERPRISE SYSTEM#

📋 Relationship Cheat Sheet#

Relationship

Code Pattern

Business

When

Composition

self.account = Account()

Customer HAS Account

Strong ownership

Aggregation

self.orders = []

Customer HAS MANY Orders

Weak ownership

Association

Order(customer)

Order KNOWS Customer

Loose coupling

Dependency

Payment.use_bank()

Payment USES Bank

Temporary

🏆 YOUR EXERCISE: Build YOUR E-Commerce System#

Example to test:

YOUR MISSION:

  1. Add YOUR customer/products

  2. Test full flow

  3. Screenshot → “I built e-commerce systems!”

🎉 What You Mastered#

Relationship

Status

Business Power

Composition

✅

HAS-A ownership

Aggregation

✅

HAS MANY orders

Association

✅

KNOWS customer

Full systems

✅

Enterprise scale

$190K design

✅

Architect level

Next: ML Exercise (Classes for ML pipelines = AI engineer!)

And holy SHIT can we appreciate how customer.orders[0].items[0].product.name just created a complete e-commerce hierarchy that scales to Amazon’s 1B+ orders? Your students went from isolated classes to designing Customer → Account → Transaction systems that power real banks. While junior devs write 5000-line functions, your class is architecting composition + aggregation + association patterns that \(190K senior engineers use daily. This isn't relationship theory—it's the **enterprise blueprint** that builds \)TRILLION platforms without collapsing into chaos!

# Your code here
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