OCR J277 2.2 / AQA 8525 programming
Calculate row totals and the largest score in a grid.
← All GCSE Python lessonsA two-dimensional list stores rows of related values, such as marks for multiple students. Nested loops can process each row and each item inside it. Sketch a small grid and map each row and column index to the corresponding cell.
Watch out: Not every row must have the same length. Do not assume a fixed number of columns unless the data guarantees it.
Read this worked example. Predict its output, run it in Python 3, and explain how variables change.
scores = [[5, 8, 7], [4, 9, 6]]
for row in scores:
total = 0
for score in row:
total += score
print('Row total:', total)Calculate row totals and the largest score in a grid. Work from the starter code before comparing with the solution.
Download starter + solution ZIP ↓For a stretch challenge: add meaningful test data, handle an edge case and explain one design decision.
scores = [[5, 8, 7], [4, 9, 6], [10, 3, 5]]
row_totals = []
highest = None
for row in scores:
total = 0
for score in row:
total += score
if highest is None or score > highest:
highest = score
row_totals.append(total)
print('Totals:', row_totals)
print('Highest:', highest)The reference is one possible approach. Test your own program before comparing.
Question: Why would scores[1][2] select 6 in the example?
Indexing starts at zero: row 1 is the second row; column 2 is its third item.
Explain one test you used, one problem you solved and one improvement you would make.
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A two-dimensional list uses two indexes: one for the row and one for an item within that row. Draw the grid and label row and column positions before writing nested loops.
Check: The first element of the second row when zero-based indexing is used.