5 파이썬의 오류 처리 패턴 (Try-Excrect 이상)

def process_user_record(record, record_number):
    if not record.get("email"):
        raise ValueError(f"Record #{record_number} failed: Missing email in record {record}")
    
    # Simulate processing
    print(f"Processed user #{record_number}: {record['email']}")

def process_users(records):
    errors = []
    for index, record in enumerate(records, start=1):  
        try:
            process_user_record(record, index)
        except ValueError as e:
            errors.append(str(e))
    return errors

users = [
    {"email": "[email protected]"},
    {"email": ""},
    {"email": "[email protected]"},
    {"email": ""}
]

errors = process_users(users)

if errors:
    print("\nProcessing completed with errors:")
    for error in errors:
        print(f"- {error}")
else:
    print("All records processed successfully")

Output:
Processed user #1: [email protected]
Processed user #3: [email protected]

Processing completed with errors:
- Record #2 failed: Missing email in record {'email': ''}
- Record #4 failed: Missing email in record {'email': ''}

import csv

def read_csv_data(file_path):
    try:
        with open(file_path, 'r') as file:
            print(f"Inside 'with': file.closed = {file.closed}")  # Should be False
            reader = csv.reader(file)
            for row in reader:
                if len(row) 

Output:
Inside 'with': file.closed = False
['Name', 'Age']
['Sarwar', '30']
Error: Invalid row format
In except block: file is closed? True

class DatabaseAccessError(Exception):
    """Raised when database operations fail."""
    pass

def fetch_user(user_id):
    try:
        # Simulate database query
        raise ConnectionError("Failed to connect to database")
    except ConnectionError as e:
        raise DatabaseAccessError(f"Failed to fetch user {user_id}") from e

try:
    fetch_user(123)
except DatabaseAccessError as e:
    print(f"Error: {e}")
    print(f"Caused by: {e.__cause__}")

Output:
Error: Failed to fetch user 123
Caused by: Failed to connect to database

import random
import time

def flaky_api_call():
    # Simulate 50% chance of failure (like timeout or server error)
    if random.random() 

Output:
Attempt 1 failed: Simulated network failure. Retrying in 2 seconds...
API call succeeded: {'status': 'success', 'data': [1, 2, 3]}

class PaymentError(Exception):
    """Base class for payment-related exceptions."""
    pass

class InsufficientFundsError(PaymentError):
    """Raised when the account has insufficient funds."""
    pass

class InvalidCardError(PaymentError):
    """Raised when the card details are invalid."""
    pass

def process_payment(amount, card_details):
    try:
        if amount > 1000:
            raise InsufficientFundsError("Not enough funds for this transaction")
        if not card_details.get("valid"):
            raise InvalidCardError("Invalid card details provided")
        print("Payment processed successfully")
    except InsufficientFundsError as e:
        print(f"Payment failed: {e}")
        # Notify user to top up account
    except InvalidCardError as e:
        print(f"Payment failed: {e}")
        # Prompt user to re-enter card details
    except Exception as e:
        print(f"Unexpected error: {e}")
        # Log for debugging

process_payment(1500, {"valid": False})

Output:
Payment failed: Not enough funds for this transaction