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Free A-Level Computer Science guide
Read requirements and predict outputs before running code. Repair one boundary fault, preserve existing validation, then extend the report and record test evidence.
Content owner: Michael Print · Written for A-Level learners · Checked against official specifications
Explore the idea
Use an original score-report task. Record an expected result before checking a boundary change; the fixed model validates rows and applies the selected threshold.
The original task loads ID,score text rows, validates them, and reports accepted scores at or above a threshold. Valid IDs are one uppercase letter followed by two digits; scores are decimal integers from 0 to 100. The first valid occurrence of an ID is kept.
The starter deliberately uses > where the requirement says >=. Keep the solution closed, predict the boundary case, then run the supplied tests. This is independent practice, not an AQA skeleton, past-paper task or mark scheme.
AQA 7517 · 4.1 programming; 4.13 systematic problem solving; Paper 1 practice
Useful foundations
By the end, you should be able to
Read TASK.txt first. Keep the solution closed while attempting the starter. These plain-text files run locally in your chosen Python environment.
AQA: original Python task for reading, repairing, extending and testing an unfamiliar program. It does not reproduce a supplied skeleton or assert equivalence across every supported language. Test files and expected outcomes are original.
Shared foundations and optional extensions are labelled separately; this page does not claim complete coverage of the qualification.
Ignore blank lines. Reject a row with the wrong field count or ID format; reject a non-integer or out-of-range score; reject a repeated accepted ID. Preserve accepted rows in their source order and report those whose score is at least the minimum.
The supplied scores.csv contains valid scores 72, 0, 100 and 60 plus two invalid scores and one malformed row. At minimum 60, expected qualifying IDs are A11, C13 and F16. Predict this independently before inspecting actual output.
parse_rows handles format, range and uniqueness; report handles threshold validation and filtering. The file-reading/writing block catches task-file errors. Keeping the pure transformation separate makes it testable without repeatedly changing files.
Copy score_report_starter.py to score_report.py to use the tests against the starter. Read the TODO instructions in TASK.txt. The solution file uses the same name, so keep its copy separate until you have attempted the repair.
A score of 72 at threshold 60 passes both > and >=, so it cannot distinguish them. A score exactly 60 is the boundary that exposes the defect. Include 59, 60 and 61 for the comparison, alongside 0 and 100 for validation.
Retain tests for duplicate IDs, malformed records, nonnumeric scores, empty text and invalid thresholds. Expected results belong in the test plan before execution; a screenshot of output alone does not establish correctness.
| Test | Expected |
|---|---|
| F16,60 at minimum 60 | Included |
| B12,59 at minimum 60 | Accepted but not qualifying |
| D14,101 | Rejected: score |
| Second valid A11 record | Rejected: duplicate |
| Empty file | No rows; no row-validation errors |
Add an interactive threshold input that accepts only an integer from 0 to 100 and reprompts after invalid text. Keep that input loop outside report so the existing pure-function tests still run. Test empty input, text, −1, 0, 100 and 101.
A second variation sorts qualifying rows by descending score and then ID for equal scores. Test a tie and ensure original accepted rows are not silently reordered. Explain the changed requirements and run old tests as regressions after each small modification.
After attempting the task, compare the solution with the requirements and test results. AQA permits several programming languages; this resource supplies Python practice and does not establish equivalent language-specific depth for Java, C# or VB.Net.
Use relevant program extracts and labelled expected/actual results to explain a repair. Consult your examination year's instructions for the on-screen response format. Avoid copying all console text without identifying which requirement each test supports.
"""Original practice task: validate rows, then report scores >= minimum."""
import re
from pathlib import Path
def parse_rows(text):
accepted, rejected, seen = [], [], set()
for number, raw in enumerate(text.splitlines(), 1):
if not raw.strip():
continue
fields = raw.strip().split(',')
if len(fields) != 2 or not re.fullmatch(r'[A-Z][0-9]{2}', fields[0]):
rejected.append((number, 'format'))
continue
identifier, score_text = fields
if not re.fullmatch(r'[0-9]+', score_text) or not 0 <= int(score_text) <= 100:
rejected.append((number, 'score'))
continue
if identifier in seen:
rejected.append((number, 'duplicate'))
continue
seen.add(identifier)
accepted.append((identifier, int(score_text)))
return accepted, rejected
def report(text, minimum=60):
if type(minimum) is not int or not 0 <= minimum <= 100:
raise ValueError('minimum must be an integer from 0 to 100')
accepted, rejected = parse_rows(text)
rows = [(identifier, score) for identifier, score in accepted if score >= minimum]
return rows, rejected
if __name__ == '__main__':
try:
source = Path('scores.csv').read_text(encoding='utf-8')
rows, rejected = report(source)
Path('report.csv').write_text(''.join(f'{key},{score}\n' for key, score in rows), encoding='utf-8')
print(f'{len(rows)} qualifying rows; rejected: {rejected}')
except (OSError, UnicodeError) as error:
print(f'Cannot read/write task files: {error}')
Worked example
4 original questions total 14 marks. Attempt each before opening the independently written indicative marking guidance.
For minimum 60 and rows A11,59; B12,60; C13,61, state which rows qualify and identify the one that distinguishes > from >=.
Indicative answer
A file contains A11,72; A11,80; B12,101; C13,text. Under the declared rules, give accepted and rejected records.
Indicative answer
Describe a safe threshold-input extension and supply one normal, one boundary and one invalid test with expected outcomes.
Indicative answer
Specify how to sort qualifying records by descending score with ascending ID ties, and how to verify that change independently.
Indicative answer
This guide addresses AQA 7517 4.1 programming; 4.13 systematic problem solving; Paper 1 practice. Check your examination year and the complete specification for the assessment scope.
These are independently written explanations and practice questions. CompSciTutoring.co.uk is not affiliated with or endorsed by an examination board. The marking guidance is indicative; always check the syllabus for your examination year.
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Use the free examples first, then explore one-to-one tuition if guided practice would help.