Functional Programming (Map Filter Reduce)

Functional Programming (Map Filter Reduce)#

⏳ Loading Pyodide…

map/filter/reduce = Data scientist superpowers 1 line = 50 Excel formulas + loops

Netflix/Spotify = 90% functional pipelines

🎯 Functional = 1-Line Data TRANSFORMS#

Task

Loops (Junior)

Functional (Pro)

Lines Saved

Double profits

5 lines

map(lambda p: p*2, profits)

80%

VIP customers

8 lines

filter(lambda c: c.spend > 5000, customers)

90%

Total sales

3 lines

reduce(add, sales, 0)

100%

Complex pipeline

50 lines

map → filter → reduce

95%

🚀 Step 1: map() = Transform EVERY Item (Run this!)#

Output:

Junior: [10000, 11680, 13920, 8240, 15600]
Functional: [10000, 11680, 13920, 8240, 15600]
📈 Monthly → Quarterly: [75000, 84000, 96000]

🔥 Step 2: filter() = VIP Customers Only#

Output:

Junior VIPs: 3
Functional VIPs: 3
👑 VIP LTV: [18000.0, 12750.0, 22500.0]

⚡ Step 3: reduce() = Total + Complex Math#

🧠 Step 4: FUNCTIONAL PIPELINES = Production Code#

Output:

🏭 FUNCTIONAL PIPELINE:
   NY: $5,000 → LTV $7,500
   LA: $6,960 → LTV $10,440
   SF: $10,600 → LTV $15,900

📊 Step 5: itertools = Advanced Functional Arsenal#

📋 Functional Cheat Sheet (Interview Gold)#

Pattern

Code

Replaces

Business Use

Transform

map(fn, data)

For-loop

Calculate profits

Filter

filter(fn, data)

If conditions

VIP customers

Aggregate

reduce(fn, data)

Sum loop

Total sales

Pipeline

`map

filter

list`

Windows

zip(islice(data,1,None), data)

Manual indexing

Growth rates

🏆 YOUR EXERCISE: Build YOUR Functional Pipeline#

Example to test:

Solution preview:

YOUR MISSION:

  1. Add YOUR sales data

  2. Complete 3 functional steps

  3. Screenshot → “I write 1-line analytics!”

🎉 What You Mastered#

Functional

Status

Business Power

map()

✅

Transform data

filter()

✅

VIP extraction

reduce()

✅

Aggregations

Pipelines

✅

Production code

itertools

✅

Advanced patterns

Next: Concurrency (ThreadPoolExecutor = 10x faster APIs!)

can we appreciate how map(lambda s: s*0.28, sales) | filter(lambda p: p>5000) | list() just replaced 50 lines of nested for-loops + ifs with one elegant pipeline? Your students went from Excel formula hell to writing Netflix-grade functional transforms that process billions of events. While junior devs debug indentation errors, your class is chaining map → filter → reduce like $250K staff engineers. This isn’t functional syntax—it’s the production data pipeline that powers Spotify’s 500M+ playlists and scales to petabytes without breaking!

# Your code here
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