2.8 Validation

Definition: Validation is the process of checking that input data is reasonable, sensible, and acceptable before processing.

Purpose: To prevent errors, incorrect processing, and potential security issues.

When used: Whenever user input or external data is entered.

Ensures that data has been entered.

Python example:

name = input("Enter name: ")

if name == "":
    print("Name is required")
        

Ensures data is within an acceptable length.

Python example:

password = input("Enter password: ")

if len(password) < 8:
    print("Password too short")
        

Ensures numeric data falls within a defined range.

Python example:

age = int(input("Enter age: "))

if age < 0 or age > 120:
    print("Age out of range")
        

Ensures data is of the correct type.

Python example:

value = input("Enter a number: ")

if not value.isdigit():
    print("Not a valid number")
        

Checks data follows a specific pattern.

Python example:

email = input("Enter email: ")

if "@" not in email:
    print("Invalid email format")
        

Uses a calculated digit to verify data accuracy.

Example use: Barcodes, ISBNs.

Simple Python concept example:

number = "1234"
check_digit = int(number[-1])

if check_digit % 2 == 0:
    print("Check digit valid")
        

Example:

mark = int(input("Enter mark: "))

if mark >= 0 and mark <= 100:
    print("Valid mark")
        

This checks that the input is within an acceptable range.

Python example:

username = input("Enter username: ")

if username != "" and len(username) >= 5:
    print("Username accepted")
else:
    print("Invalid username")
        

Incorrect code:

age = input("Enter age: ")

if age > 18:
    print("Adult")
        

Problem: Input is a string, not an integer.

Corrected code:

age = int(input("Enter age: "))

if age > 18:
    print("Adult")