How can you verify the correctness of user-input data?

Validation of user-entered data involves several steps:

• Format validation: checking if the input matches the expected format (e.g., number, email, date).
• Range and constraint checks: for example, a number should be within a certain range, a string should not be empty.
• Exception handling: when converting types (e.g., from string to number), possible errors should be handled.

In Python, validation can be performed using regular expressions, built-in functions, and try-except blocks.

Example of validating input for a number from 1 to 100:

user_input = input("Enter a number from 1 to 100: ")
try:
    value = int(user_input)
    if 1 <= value <= 100:
        print("Valid input")
    else:
        print("Number is out of the allowed range")
except ValueError:
    print("Invalid number format")

For more complex formats, the re module for regular expressions or specialized libraries (e.g., pydantic for data validation) can be used.