Python Full Stack Web Developer Course

def safe_read_file(filename, default=""):
    try:
        with open(filename, 'r') as file:
            return file.read()
    except FileNotFoundError:
        print(f"Warning: File {filename} not found.")
        return default
    except PermissionError:
        print(f"Warning: No permission to read {filename}.")
        return default
    except Exception as e:
        print(f"Unexpected error reading {filename}: {e}")
        return default

def safe_divide():
    try:
        num1 = float(input("Enter the numerator: "))
        num2 = float(input("Enter the denominator: "))
        result = num1 / num2
        print(f"{num1} divided by {num2} is {result}")
        return result
    except ValueError:
        print("Error: Please enter valid numbers.")
    except ZeroDivisionError:
        print("Error: Cannot divide by zero.")
    except KeyboardInterrupt:
        print("\nOperation cancelled by user.")
    except Exception as e:
        print(f"Unexpected error: {e}")
    
    # If we get here, an exception occurred
    return None

class BankingError(Exception):
    """Base exception for banking operations."""
    pass

class InsufficientFundsError(BankingError):
    """Raised when a withdrawal would result in a negative balance."""
    def __init__(self, account_id, requested, available):
        self.account_id = account_id
        self.requested = requested
        self.available = available
        self.deficit = requested - available
        super().__init__(
            f"Account {account_id} has insufficient funds: "
            f"requested ${requested:.2f}, available ${available:.2f}, "
            f"deficit ${self.deficit:.2f}"
        )

def withdraw(account_id, amount):
    # Get account balance (in a real app, this would be from a database)
    balance = get_account_balance(account_id)
    
    if amount <= 0:
        raise ValueError("Withdrawal amount must be positive")
    
    if balance < amount:
        raise InsufficientFundsError(account_id, amount, balance)
    
    # Perform withdrawal
    new_balance = perform_withdrawal(account_id, amount)
    return new_balance

# Usage
try:
    new_balance = withdraw("ACC123456", 500.00)
    print(f"Withdrawal successful. New balance: ${new_balance:.2f}")
except ValueError as e:
    print(f"Invalid withdrawal: {e}")
except InsufficientFundsError as e:
    print(f"Withdrawal failed: {e}")
    print(f"Would you like to withdraw ${e.available:.2f} instead?")
except BankingError as e:
    print(f"Banking error: {e}")
except Exception as e:
    print(f"Unexpected error: {e}")

import time
import logging
from contextlib import contextmanager

# Configure logging
logging.basicConfig(level=logging.INFO)

@contextmanager
def timing(description):
    start_time = time.time()
    try:
        yield
    finally:
        elapsed_time = time.time() - start_time
        logging.info(f"{description}: {elapsed_time:.4f} seconds")

# Usage
with timing("Data processing"):
    # Code to time
    data = process_large_dataset()

with timing("API request"):
    # Another operation to time
    response = api.get_data()