Python: Loops, Lists and Functions: Unit Exam A
for and while loops, lists and indexes, append and len, functions with parameters and return values, and validation.
Instructions
- Time allowed
- 25 minutes
- Total marks
- 25
- Calculator
- No calculator is permitted.
- Answer all the questions.
- The number of marks for each question is shown in brackets. Use it as a guide to how much to write.
- The clock at the top counts down from the real time allowed. When it reaches zero the paper is locked and marked, as it would be collected in the exam hall.
- Read every question to the end before answering. Where a question says tick two boxes, tick exactly two: ticking more than asked scores nothing. Type one word and number answers carefully, because they are marked exactly.
Questions
Answer every question, then finish the paper to have it marked. Marking as you go teaches you far less.
for i in range(3):
print("Hi")- L3
range(3) gives 0, 1 and 2: three passes.
for i in range(1, 5):
print(i)- L4
range(1, 5) stops before 5, so the last value is 4.
total = 0
for n in range(1, 6):
total = total + n
print(total)- L15
1 + 2 + 3 + 4 + 5 = 15.
- Lred
- Lblue
- Lyellow
- L4
Indexes start at 0, so colours[0] is red and colours[2] is blue. -1 is the last item, yellow. There are 4 items.
Tick one box.
- LA colours.append("purple")
append() adds to the end. colours[4] would be an error, because the list has no index 4 yet.
Tick one box.
- LC A loop whose condition never becomes false, so it never stops
If nothing inside the loop ever makes the condition false, it runs for ever.
x = 1
while x < 50:
x = x * 2
print(x)- L64
x doubles: 2, 4, 8, 16, 32, 64. 64 is not below 50, so the loop stops and 64 is printed.
Tick one box.
- LB A while loop
A while loop repeats until its condition changes.
def double(n):
return n * 2
print(double(4) + double(3))- L14
double(4) returns 8 and double(3) returns 6: 8 + 6 = 14.
| Parameter | Function call | Return value | |
|---|---|---|---|
| n in def double(n): | |||
| double(4) | |||
| The value worked out by n * 2 and sent back |
Tick one box in each row.
- Ln in def double(n):: Parameter
- Ldouble(4): Function call
- LThe value worked out by n * 2 and sent back: Return value
n is the parameter, double(4) calls the function, and n * 2 is sent back as the return value.
- LDefines a function called area with two parameters
- LReturns the correct area, for example 12 for a width of 3 and a height of 4
- LReturns the value rather than printing it
Multiply the width by the height and return the result.
def area(width, height):
return width * height- LChecking that input is sensible or follows the rules before it is used
- LA named check, such as a range, length, presence or type check
Validation is the program checking that input is sensible, and follows the rules, before using it. A range check, for example, rejects an age outside 11 to 18.
for i in range(2, 11, 4):
print(i)| Line | Printed |
|---|---|
| 1 | |
| 2 | |
| 3 |
- L2
- L6
- L10
range(2, 11, 4) starts at 2 and goes up in 4s, stopping before 11: 2, 6, 10.
Tick one box.
- LD 8
Index 1 is the second item, 8.
scores = [3, 7, 2]
scores.append(5)
print(len(scores))- L4
Appending 5 makes four items.
This is an original Key Stage 3 assessment. Most questions are closed, so the marking is exact, and the written answers are marked against a mark scheme in the same style as a GCSE paper, so the format is familiar long before it counts.