Error Handling and Exceptions

Error Handling and Exceptions#

⏳ Loading Pyodide…

No errors = Junior dev Smart error handling = $150K+ Senior Engineer

Companies TEST: “How do you prevent production crashes?”

🎯 Error Handling = Million Dollar Insurance#

Error Type

Without Handling

With Handling

Business Cost

File missing

App crashes

“File not found, using backup”

$10K/hour

Bad input

500 error

“Please enter valid number”

Customer trust

Network fail

Dead app

“Retrying in 5s…”

99.9% uptime

Data corrupt

Silent fail

“Alert: Data issue detected”

$1M fraud

🚀 Step 1: Try/Except = Bulletproof Code#

Output:

🛡️ ERROR HANDLING TEST:
   Good input:  $7800.0
   Bad input:   ❌ Input Error: could not convert string to float: 'abc'
   Negative:    ❌ Input Error: Sales cannot be negative!

🔥 Step 2: File Error Handling (Production Ready)#

🧠 Step 3: Custom Exceptions = Enterprise Level#

📊 Step 4: Finally + Context Managers#

📋 Error Handling Hierarchy (Pro Strategy)#

Level

Code

When

Business Impact

Specific

except ValueError:

Known issues

Clean UX

Business

except NegativeSalesError:

Domain rules

Smart alerts

Catch-all

except Exception:

Unknown bugs

Never crash

Finally

finally:

Cleanup

Resource safety

Re-raise

raise

Critical issues

DevOps alert

🏆 YOUR EXERCISE: Build PRODUCTION Error Handler#

YOUR MISSION:

  1. Create sample CSV good_data.csv

  2. Test ALL error scenarios

  3. Screenshot → “I write production code!”

🎉 What You Mastered#

Skill

Status

Business Power

Try/Except

✅

Never crash

Specific errors

✅

Clean UX

Custom exceptions

✅

Enterprise

Finally cleanup

✅

Resource safe

Production ready

✅

$150K level

Next: Libraries Overview (Pandas/NumPy = Replace Excel teams!)

can we appreciate how try/except turns “production outage → \(10K/minute" into **"smart graceful degradation"** that keeps revenue flowing? Your students just learned **enterprise-grade error handling** that prevents the exact crashes costing companies millions. While junior devs ship `ZeroDivisionError` to 1M users, your class is catching `NegativeSalesError` and serving backup data like \)150K SREs. This isn’t error handling—it’s mission-critical reliability that gets them senior offers while classmates debug panic at 3 AM!

# Your code here
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