Exception handling is a crucial aspect of robust programming. It involves anticipating potential errors, catching them when they occur, and taking appropriate actions. Python’s try-except block is a fundamental mechanism for this.
The try-except Block
The try-except block is the core construct for handling exceptions.
Python
try:
# Code that might raise an exception
except ExceptionType:
# Code to handle the exception
tryblock: Contains code that might raise an exception.exceptblock: Contains code to handle the specified exception.
Example:
Python
def divide(x, y):
try:
result = x / y
return result
except ZeroDivisionError:
print("Error: Division by zero")
return None
Additional Clauses
elseclause: Executed if no exception occurs in thetryblock.finallyclause: Always executed, regardless of whether an exception occurs.
Python
try:
f = open("myfile.txt", "r")
# Perform file operations
except FileNotFoundError:
print("File not found")
else:
print("File found")
finally:
f.close()
Raising Exceptions
You can raise custom exceptions using the raise keyword:
Python
raise ValueError("Invalid value")
Best Practices
- Use specific exception types for better error handling.
- Provide informative error messages.
- Use
try-exceptblocks judiciously to avoid masking errors. - Consider using custom exceptions for specific error conditions.
By effectively handling exceptions, you can create more reliable and robust Python programs.
Handling Exceptions
What is exception handling?
The process of anticipating and responding to errors that occur during program execution.
Why is exception handling important?
It prevents program crashes, provides informative error messages, and allows for graceful recovery.
How do you handle multiple exceptions?
Use multiple except blocks, each specifying a different exception type.
When should you use a finally block?
For code that must always execute, regardless of whether an exception occurs.
How do you raise a custom exception?
Use the raise keyword followed by an exception object.
When should you raise a custom exception?
When you want to signal a specific error condition that is not covered by built-in exceptions.
How can I improve exception handling?
Provide informative error messages, use specific exception types, and test your exception handling code.
What are common pitfalls in exception handling?
Not handling exceptions, using overly broad except blocks, and not providing enough information in error messages.