Validation checks

301.16 Defensive Design

Defensive Design — Note 2 of 5

Range length presence.

What you need to know

Validation checks ensure data meets specific criteria before processing. Common checks include range (within limits), length (correct size), and presence (not empty).

What to know

Range check: 0 <= age and age <= 120
Length check: len(password) >= 8
Presence check: name != ""
Type check: value.isdigit()
Use while loops to re-ask until valid

Code examples

Validation loop

python

age = -1
while age < 0 or age > 120:
    age = int(input("Enter age (0-120): "))
    if age < 0 or age > 120:
        print("Out of range, try again")
print("Age: " + str(age))

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Specification notes for programming are in Paper 2.