raise Statements

Introduction to raise Statements

In Python programming, errors and exceptions are part of the routine process and act as debug-friendly alerts. To invoke exceptions manually or highlight exigent conditions, Python allows the usage of raise statements.

The raise statement, in Python, allows the programmer to force a specified exception to occur. It gives the ability to stop program execution when an external condition is triggered or when a bug is introduced.

Building of raise Statements

Here’s how a raise statement is typically built:

1raise Exception("Description of the error/ exception")

In the example above, ‘Exception’ is a built-in, base class for all exceptions and “Description of the error/ exception” is an informative message that explains the cause of the error.

Implementing raise Statements in Python

Let’s look at a simple implementation of the raise statement in Python:

1x = -1
2if x < 0:
3  raise Exception("Sorry, no numbers below zero")

In this code, we’re raising an exception when the variable x is less than 0. Hence, running this code would throw an error, Exception: Sorry, no numbers below zero.

Custom Exceptions

Generally, Python’s built-in exceptions are used to raise exceptions. Nevertheless, users can also define their own exceptions by creating a new exception class which inherits from the base Exception class.

Here is an example demonstrating how this can be done:

1class CustomError(Exception):
2    pass
4raise CustomError("This is a custom exception")

In the example above, CustomError is our own exception class which is derived from Python’s exception base class, Exception.


The pass in Python means “do nothing”. It is used when a statement is required syntactically but the program requires no action.

Remember, the choices of handling exceptions entirely depend on the needs of your specific program. Being proficient with Python’s error and exception handling can greatly improve the robustness of your code. Keep experimenting!