Error Handling

Learning how to handle exceptions using try-except blocks.

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1

What is the purpose of a try-except block in Python?

try:
    # Code that might raise an exception
    result = 10 / 0
except ZeroDivisionError:
    # Code that runs if an exception occurs
    print("Cannot divide by zero")

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2

How do you catch multiple exceptions in a single except block?

try:
    # Code that might raise exceptions
    result = int("not a number")
except (ValueError, TypeError) as e:
    print(f"An error occurred: {e}")

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3

How do you use else in a try-except block?

try:
    result = 10 / 2
except ZeroDivisionError:
    print("Cannot divide by zero")
else:
    print("Division successful, result is:", result)

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4

What is the use of finally in exception handling?

try:
    file = open("example.txt", "r")
    content = file.read()
except FileNotFoundError:
    print("File not found")
finally:
    file.close()
    print("File has been closed")

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5

How can you access the exception object in an except block?

try:
    result = int("abc")
except ValueError as e:
    print(f"An error occurred: {e}")

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6

How do you re-raise an exception after catching it?

try:
    result = int("not a number")
except ValueError as e:
    print("Handling exception...")
    raise

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7

Can you catch all exceptions using a generic except block?

try:
    result = 10 / 0
except Exception as e:
    print(f"An unexpected error occurred: {e}")

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8

How do you create a custom exception in Python?

class CustomError(Exception):
    pass

try:
    raise CustomError("This is a custom exception")
except CustomError as e:
    print(f"Caught custom exception: {e}")

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9

How do you handle exceptions in a loop?

numbers = [10, 0, 5, 'a']
for num in numbers:
    try:
        result = 10 / num
        print(f"10 divided by {num} is {result}")
    except (ZeroDivisionError, TypeError) as e:
        print(f"Error: {e}")

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10

How can you use try-except to validate user input?

while True:
    try:
        age = int(input("Enter your age: "))
        break
    except ValueError:
        print("Please enter a valid integer.")

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11

How can you use try-except to handle file I/O errors?

try:
    with open("nonexistent_file.txt", "r") as file:
        content = file.read()
except IOError as e:
    print(f"File error: {e}")

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12

What is the difference between except and finally blocks?

try:
    result = 10 / 2
except ZeroDivisionError:
    print("Error occurred")
finally:
    print("This will always execute, regardless of errors")

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13

How do you handle exceptions for a specific line of code?

try:
    result = 10 / 2
    result = int("abc")
except ValueError:
    print("ValueError occurred")
except ZeroDivisionError:
    print("ZeroDivisionError occurred")

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14

How can you use multiple except blocks for different exceptions?

try:
    result = 10 / 0
except ZeroDivisionError:
    print("Cannot divide by zero")
except ValueError:
    print("Value error occurred")

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15

How do you handle exceptions in nested try-except blocks?

try:
    try:
        result = 10 / 0
    except ZeroDivisionError:
        print("Inner block: Division by zero")
except Exception:
    print("Outer block: General exception")

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16

How do you ignore certain exceptions while handling others?

try:
    result = int("not a number")
except ValueError:
    print("Handling ValueError")
except (TypeError, KeyError):
    pass  # Ignore TypeError and KeyError

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17

How can you use try-except with with statements?

try:
    with open("example.txt", "r") as file:
        content = file.read()
except FileNotFoundError:
    print("File not found")

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18

How do you log exceptions in a try-except block?

import logging

logging.basicConfig(level=logging.ERROR)

try:
    result = 10 / 0
except ZeroDivisionError as e:
    logging.error("An error occurred: %s", e)

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19

How do you handle exceptions in a function and propagate them to the caller?

def divide_numbers(a, b):
    try:
        return a / b
    except ZeroDivisionError:
        print("Handled in function")
        raise

try:
    result = divide_numbers(10, 0)
except ZeroDivisionError:
    print("Handled in caller")

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20

How do you use try-except to handle exceptions in multithreaded code?

import threading

def thread_func():
    try:
        result = 10 / 0
    except ZeroDivisionError:
        print("Exception in thread")

thread = threading.Thread(target=thread_func)
thread.start()
thread.join()

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21

How do you handle exceptions in asynchronous code with async and await?

import asyncio

async def async_func():
    try:
        result = 10 / 0
    except ZeroDivisionError:
        print("Exception in async function")

asyncio.run(async_func())

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22

How do you handle exceptions in a finally block?

try:
    result = 10 / 2
finally:
    print("This block always executes, even if there was an exception")

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23

How do you use try-except with else and finally together?

try:
    result = 10 / 2
except ZeroDivisionError:
    print("Exception occurred")
else:
    print("No exception occurred, result is", result)
finally:
    print("This always executes")

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24

How do you handle exceptions when using external libraries or APIs?

import requests

try:
    response = requests.get("https://example.com")
    response.raise_for_status()
except requests.exceptions.HTTPError as e:
    print(f"HTTP error occurred: {e}")
except requests.exceptions.RequestException as e:
    print(f"Request error occurred: {e}")

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25

How do you validate that an exception was correctly caught and handled?

try:
    raise ValueError("Test exception")
except ValueError as e:
    print(f"Exception caught: {e}")
finally:
    assert "Test exception" in str(e), "Exception message did not match"

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