Exception Handling in Python

What is an Exception?

An exception is an event that occurs during the execution of a program that disrupts the normal flow of instructions. When an error occurs, Python generates an exception that can be handled, which avoids the program from crashing.

Types of Exceptions

There are two types of exceptions in Python:

Syntax Error: These errors occur when the parser detects a syntax error. For example, if you forget to close a bracket or misspell a keyword, Python will raise a syntax error.
Exceptions: These errors occur during the execution of the program. For example, if you try to divide a number by zero, Python will raise an exception.

Handling Exceptions

To handle exceptions in Python, you can use the try, except, and finally blocks. The try block contains the code that might raise an exception, and the except block contains the code that handles the exception. The finally block contains the code that will be executed regardless of whether an exception is raised or not.

try:
  # code that might raise an exception
  x = 10 / 0
except ZeroDivisionError:
  # code that handles the exception
  print("Cannot divide by zero!")
finally:
  # code that will be executed regardless of whether an exception is raised or not
  print("The program has ended.")

$ python main.py
 
Cannot divide by zero!
The program has ended.

Raising Exceptions

You can raise exceptions in Python using the raise statement. This allows you to create custom exceptions and handle them in your code.

x = -1
 
if x < 0:
  raise Exception("Number cannot be negative!")

$ python main.py
 
Traceback (most recent call last):
  File "main.py", line 4, in <module>
    raise Exception("Number cannot be negative!")
Exception: Number cannot be negative!

Conclusion

In this guide, you learned about exception handling in Python. You learned about the different types of exceptions, how to handle exceptions using the try, except, and finally blocks, and how to raise exceptions using the raise statement. Exception handling is an essential concept in Python programming that allows you to handle errors gracefully and prevent your program from crashing.

References

Collections Python Standard Libraries