Range checking in code

Name:

Date:

Class:

Quick Questions

Shade in the A or B circle for each question.

1. Which condition is a range check that accepts ages from 1 to 120 inclusive?

A if age == 1 or 120:

B if 1 <= age <= 120:

2. A program uses the check 1 <= age <= 120. Which age is rejected as invalid?

A 120

B 121

3. What does a range check test?

A That a number lies between a minimum and a maximum

B That a value is not left empty

4. You want a mark of 0 to be valid for a test scored out of 100. Which check is correct?

A if 0 <= mark <= 100:

B if 0 < mark <= 100:

5. Which range check is better practice for a maximum quantity limit?

A if MIN_QTY <= qty <= MAX_QTY:

B if 1 <= qty <= 50:

Match the Pairs

Draw a line connecting each item on the left to its match on the right.

Left column		Right column
1if 1 <= age <= 120:		AUses < instead of <=, so the boundary values 1 and 120 are wrongly rejected when the range should be inclusive.
2if MIN_AGE <= age <= MAX_AGE:		BChecks that age is between 1 and 120, including both limits
3Inclusive boundaries: the minimum and maximum values themselves are accepted		Cvalid = 1 <= mark <= 100
4A range check on a date: the date must fall between a start date and an end date		DRange check that uses named constants for the lower and upper limits
5if 1 < age < 120:		Eif date(2025, 1, 1) <= entry <= date(2025, 12, 31):
6if age >= 1 or age <= 120:		FUses or instead of and, so almost every number passes, including 0 and 121. Both limits must be satisfied together.

Definitions

1 <= age <= 120

Fill in the Blanks

Complete each line of code by filling in the missing parts.

if 1 <= age __ 120: print("Valid age")

LOW = 1 HIGH = 120 if LOW <= age <= ____:

entry = "2026-06-15" if "2026-01-01" <= _____ <= "2026-12-31":

if age < 1 __ age > 120: print("Invalid age")

age = int(input("Age: ")) while ___ 1 <= age <= 120: age = int(input("Try again: "))

Spot the Error

Shade in the letter of the line that contains an error.

Question 1

A age = int(input("Age: "))

B if 1 <= age >= 120:

C print("Valid")

D else:

E print("Invalid")

Question 2

A MIN = 1

B MAX = 120

C if age < MIN and age > MAX:

D print("Out of range")

Question 3

A score = input("Score: ")

B if 0 <= score <= 100:

C print("Accepted")

Question 4

A temp = float(input("Temp: "))

B if 50 <= temp <= -10:

C print("OK")

D else:

E print("Rejected")

Question 5

A MAX_MARK == 50

B mark = int(input("Mark: "))

C if 0 <= mark <= MAX_MARK:

D print("Valid")

Answer Key

Range checking in code

Section A: Quick Questions

B — if 1 <= age <= 120:

B — 121

A — That a number lies between a minimum and a maximum

A — if 0 <= mark <= 100:

A — if MIN_QTY <= qty <= MAX_QTY:

Section B: Match the Pairs

if 1 <= age <= 120: → Checks that age is between 1 and 120, including both limits

if MIN_AGE <= age <= MAX_AGE: → Range check that uses named constants for the lower and upper limits

Inclusive boundaries: the minimum and maximum values themselves are accepted → valid = 1 <= mark <= 100

A range check on a date: the date must fall between a start date and an end date → if date(2025, 1, 1) <= entry <= date(2025, 12, 31):

if 1 < age < 120: → Uses < instead of <=, so the boundary values 1 and 120 are wrongly rejected when the range should be inclusive.

if age >= 1 or age <= 120: → Uses or instead of and, so almost every number passes, including 0 and 121. Both limits must be satisfied together.

Section C: Definitions

1 <= age <= 120 — A range check: tests that a number lies between a minimum and a maximum (inclusive here). Values outside the limits, such as 0 or 121, are rejected as invalid.

Section D: Fill in the Blanks

if 1 <= age <= 120:
    print("Valid age")

LOW = 1
HIGH = 120
if LOW <= age <= HIGH:

entry = "2026-06-15"
if "2026-01-01" <= entry <= "2026-12-31":

if age < 1 or age > 120:
    print("Invalid age")

age = int(input("Age: "))
while not 1 <= age <= 120:
    age = int(input("Try again: "))

Section E: Spot the Error

B — The second operator points the wrong way. 'age >= 120' only accepts ages of 120 or more, so most valid ages fail. The upper limit must be 'age <= 120'.

C — No number is both below the minimum and above the maximum, so 'and' never triggers and invalid values slip through. Use 'or' to reject a value outside either limit.

A — input() returns a string, so comparing it with numbers causes a TypeError. Convert it first with int(): score = int(input("Score: ")).

B — The limits are swapped. The minimum must come first and the maximum last, so it should be 'if -10 <= temp <= 50:'. As written, no value can pass.

A — A single = assigns a value to the constant. '==' only compares, so MAX_MARK is never created and the range check fails with a NameError. It should be MAX_MARK = 50.