How is data validation performed before processing?

Data validation before processing in Python typically involves verifying input values for compliance with the expected format, type, and range. This can be done using:

• Type checks with isinstance().
• Using try-except blocks to catch errors during data conversion.
• Validation with regular expressions for strings.
• Using third-party libraries, such as pydantic or marshmallow, for more complex validation schemas.

Example of simple type and range check:

def process_age(age):
    if not isinstance(age, int):
        raise ValueError("Age must be an integer")
    if age < 0 or age > 120:
        raise ValueError("Age is out of the valid range")
    # further processing

Thus, data validation helps prevent runtime errors and ensures the correctness of the program.