\nFileNotFoundError<\/td>\n File does not exist<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\nUnderstanding these exceptions helps developers create more robust Python programs<\/b>.<\/p>\nRaising Exceptions in Python<\/h2>\n
Python allows developers to raise exceptions manually using the raise keyword<\/b>.<\/p>\n
Example:<\/p>\n
def check_value(value):\r\n\u00a0\u00a0\u00a0if value < 0:\r\n\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0raise ValueError(\"Value must be non-negative\")\r\n\u00a0\u00a0\u00a0print(\"Value:\", value)\r\nUsage:\r\ntry:\r\n\u00a0\u00a0\u00a0check_value(-5)\r\nexcept ValueError as e:\r\n\u00a0\u00a0\u00a0print(\"Error:\", e)\r\nOutput:\r\nError: Value must be non-negative<\/code>Copy<\/button><\/pre>\nThis technique is useful for validating user input and enforcing program rules<\/b>.<\/p>\nCustom Exceptions in Python<\/h2>\n
Python also allows developers to create custom exception classes<\/b>.<\/p>\n
Example:<\/p>\n
class CustomError(Exception):\r\n\u00a0\u00a0\u00a0pass\r\nUsage:\r\ntry:\r\n\u00a0\u00a0\u00a0raise CustomError(\"Custom error occurred\")\r\nexcept CustomError as e:\r\n\u00a0\u00a0\u00a0print(\"Caught error:\", e)\r\nOutput:\r\nCaught error: Custom error occurred<\/code>Copy<\/button><\/pre>\nCustom exceptions are commonly used in large applications and frameworks<\/b>.<\/p>\nPython Exception Handling Cheat Sheet<\/h2>\n<\/div>\n
\n
\n\n\nStatement<\/b><\/td>\n Purpose<\/b><\/td>\n<\/tr>\n\ntry<\/td>\n Wrap code that may cause errors<\/td>\n<\/tr>\n \nexcept<\/td>\n Handle the error<\/td>\n<\/tr>\n \nelse<\/td>\n Runs when no error occurs<\/td>\n<\/tr>\n \nfinally<\/td>\n Always executes<\/td>\n<\/tr>\n \nraise<\/td>\n Manually trigger an exception<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\nThis cheat sheet is helpful when learning Python error handling quickly<\/b>.<\/p>\nBest Practices for Exception Handling in Python<\/h2>\nCatch Specific Exceptions<\/h3>\n
Avoid using a generic except block.<\/p>\n
Bad practice:\r\nexcept:\r\n\u00a0\u00a0\u00a0pass\r\nBetter approach:\r\nexcept ValueError:<\/code>Copy<\/button><\/pre>\nKeep Try Blocks Small<\/h3>\n Smaller try blocks make debugging easier.<\/p>\n
Use Meaningful Error Messages<\/h3>\n Clear messages improve user experience and debugging.<\/p>\n
Use Logging in Production<\/h3>\n Use the Python logging module<\/b> instead of printing errors.<\/p>\nReal World Example of Python Exception Handling<\/h2>\n
Example: Handling invalid user input.<\/p>\n
try:\r\n\u00a0\u00a0\u00a0number = int(input(\"Enter a number: \"))\r\n\u00a0\u00a0\u00a0result = 10 \/ number\r\n\u00a0\u00a0\u00a0print(result)\r\nexcept ValueError:\r\n\u00a0\u00a0\u00a0print(\"Invalid input. Please enter a number.\")\r\nexcept ZeroDivisionError:\r\n\u00a0\u00a0\u00a0print(\"Division by zero is not allowed.\")<\/code>Copy<\/button><\/pre>\nThis prevents the program from crashing due to user mistakes.<\/p>\n
Q) What is exception handling in Python?<\/b><\/p>\n
A) Exception handling in Python is a mechanism used to detect and manage runtime errors using try and except blocks so that the program can continue executing instead of crashing.<\/p>\n
Q) What are exceptions in Python?<\/b><\/p>\n
A) Exceptions are errors that occur during program execution and interrupt the normal flow of the program. Examples include division by zero, invalid input, and file access errors.<\/p>\n
Q) What are the main blocks used for exception handling in Python?<\/b><\/p>\n
A) Python uses four main blocks for exception handling:<\/p>\n
\ntry<\/li>\n except<\/li>\n else<\/li>\n finally<\/li>\n<\/ul>\nEach block helps manage errors and control program execution.<\/p>\n
Q) What does the try block do in Python?<\/b><\/p>\n
A) The try block contains code that may produce an exception. If an error occurs inside the try block, Python immediately stops executing it and jumps to the appropriate except block.<\/p>\n
Q) What does the except block do in Python?<\/b><\/p>\n
A) The except block catches and handles exceptions raised in the try block. It allows developers to display error messages or perform recovery actions.<\/p>\n
Q) What is the purpose of the else block in Python exception handling?<\/b><\/p>\n
A) The else block runs only when the try block executes successfully without raising any exceptions.<\/p>\n
Q) What does the finally block do in Python?<\/b><\/p>\n
A) The finally block always executes whether an exception occurs or not. It is commonly used for cleanup operations such as closing files or releasing resources.<\/p>\n
Q) Can Python handle multiple exceptions?<\/b><\/p>\n
A) Yes. Python allows multiple except blocks to handle different types of exceptions separately.<\/p>\n
Example:<\/p>\n
try:\r\n\u00a0\u00a0\u00a0# code\r\nexcept ValueError:\r\n\u00a0\u00a0\u00a0# handle value error\r\nexcept TypeError:\r\n\u00a0\u00a0\u00a0# handle type error<\/code>Copy<\/button><\/pre>\nQ) What is the raise keyword in Python?<\/b><\/p>\n
A) The raise keyword is used to manually trigger an exception in Python. It allows developers to enforce rules or validate input data.<\/p>\n
Example:<\/p>\n
raise ValueError(“Invalid input”)<\/p>\n
Q) What are custom exceptions in Python?<\/b><\/p>\n
A) Custom exceptions are user-defined exception classes created by inheriting from the built-in Exception class. They help developers create application-specific error types.<\/p>\n
Q) What is the difference between error and exception in Python?<\/b><\/p>\n
A) An error is a general issue that prevents code from running correctly, while an exception is a specific runtime error that Python can detect and handle using exception handling.<\/p>\n
Q) Why is exception handling important in Python?<\/b><\/p>\n
A) Exception handling prevents programs from crashing unexpectedly and helps developers manage errors gracefully, improving application reliability.<\/p>\n
Q) Can we use multiple except blocks in Python?<\/b><\/p>\n
A) Yes. Python allows multiple except blocks to handle different types of exceptions individually.<\/p>\n
Q) What happens if an exception is not handled in Python?<\/b><\/p>\n
A) If an exception is not handled, Python stops program execution and displays an error message along with a traceback.<\/p>\n
Q) Can try be used without except in Python?<\/b><\/p>\n
A) Yes. A try block can be used with finally without an except block when cleanup actions are required regardless of errors.<\/p>\n
Example:<\/p>\n
try:\r\n\u00a0\u00a0\u00a0file = open(\"data.txt\")\r\nfinally:\r\n\u00a0\u00a0\u00a0file.close()<\/code>Copy<\/button><\/pre>\nQ) What is a common example of exception handling in Python?<\/b><\/p>\n
A) A common example is handling division by zero errors.<\/p>\n
Example:<\/p>\n
try:\r\n\u00a0\u00a0\u00a0result = 10 \/ 0\r\nexcept ZeroDivisionError:\r\n\u00a0\u00a0\u00a0print(\"Division by zero is not allowed\")<\/code>Copy<\/button><\/pre>\nQ) What are common exceptions in Python?<\/b><\/p>\n
A) Some common Python exceptions include:<\/p>\n