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Records, rows, fields and two-dimensional structures

A two-dimensional structure stores rows containing related fields. In Python's PLS representation, it is a list of lists. The first index selects a row; the second selects a field inside that row.

1. Read row then field

In records[1][2], index 1 selects Ben's row and index 2 selects the score field. Each row should follow the same field order. A whole row represents one record; a column position represents one kind of field.

Fill in the blanks3 marks

The first index chooses a gap 1. The second chooses a gap 2 inside it. For three rows, the final row index is gap 3.

2
field
row

Multiple choice1 mark

Given records = [["A", 4], ["B", 7]], what is records[1][0]?

2. Preserve field meaning and type

A record may contain mixed types: a name string, an integer score and a Boolean membership flag. CSV input begins as text, but after parsing, numeric fields should be converted so comparisons and arithmetic behave correctly.

Written answer2 marks

For clubs = [["Mina", "Chess", 6], ["Owen", "Code", 8]], state the expressions that access Code and 6.

Give one two-index expression for each value.

Students type their answer here.

3. Predict before execution

records = [["Asha", 12], ["Ben", 18], ["Cara", 14]]
total = 0
for row in records:
    total = total + row[1]
print(total)

Multiple choice1 mark

What exact value is printed?

A3
B14
C44
D121814

Written answer2 marks

Explain why row[1] changes on each loop pass even though the expression is unchanged.

Refer to the current row variable.

Students type their answer here.

Trace table5 marks

Complete the row-traversal trace.

Record row, score and total each iteration.

Use one row for each pass through the loop. Fill in a box only when that value changes on that row, and leave the rest blank.

ProgramPython

records = [["A", 3], ["B", 5], ["C", 2]]
total = 0
for row in records:
score = row[1]
total = total + score
print(total)

Trace table with 5 columns
Row	records	total	row	score	Output
1
2
3
4
5
6
7

Written answer2 marks

Explain why a two-dimensional structure is more suitable than three unrelated lists for records that must be processed row by row.

Link grouped fields to consistency or traversal.

Students type their answer here.

Multiple choice1 mark

Which statement is accurate?

AEvery 2D structure is a database
BThe first index always means a column
CA row can hold related fields in a fixed order
DAll fields must be strings

Route forward

You can access rows and fields reliably. Next you will use nested traversal, formatted display and linear search over a named field.