A3.1 Arrays, records and tuples worksheet

Arrays in one, two and three dimensions, records and fields, tuples and lists, and static structures.

Questions 6 marks in all

[1 mark]Which of these describes an array?

AA fixed-size, indexed collection of elements of the same data type
BA collection of named fields that can have different data types
CAn immutable ordered collection of values of any types
DA collection of key-value pairs

[1 mark]What does this program print?

scans = [[[1, 2], [3, 4]], [[5, 6], [7, 8]], [[9, 10], [11, 12]]]
print(len(scans), len(scans[0]), len(scans[0][0]))
print(scans[2][0][1])

[1 mark]A two-dimensional array with 8 columns is stored in row-major order, starting at position 0. At what position is element [3][5]?

[1 mark]BugBot's position() returns a tuple rather than a list. Which is the best reason?

AA tuple is immutable, so the x and y cannot be changed separately by mistake
BA tuple can hold more values than a list
CA tuple is sorted automatically
DA tuple can only hold numbers

[1 mark]What does this program print?

grid = [[0] * 2] * 3
grid[1][0] = 7
print(grid)

[1 mark]Which of these are true of a record?

Tick every answer that is true.

AIt groups fields that can have different data types
BEach field has its own name
CAll of its fields must have the same data type
DA file is often a collection of records with the same fields

The task: the depth cube

scans is a 3D array of three saved 4 by 4 depth scans, indexed scans[scan][row][col], each value a whole number of centimetres from 1 to 100. Using nested loops and len(), print: 1. size: 3 x 4 x 4, working the three sizes out with len(). 2. For each scan s from 0 to 2, scan <s> average: <mean>, the mean of its 16 values rounded to 1 decimal place with round(value, 1), for example scan 0 average: 56.0. 3. nearest: <cm> cm at [<scan>][<row>][<col>], the smallest value and its three indexes. The smallest value appears only once. The robot does not move.

# the two lines every program starts with: the commands, then the robot
from bugbot import *
connect()

# scans[scan][row][col]: three saved 4 by 4 depth scans, in cm
scans = [
    [[45, 44, 43, 50], [40, 38, 39, 41], [60, 58, 57, 59], [80, 79, 81, 82]],
    [[44, 42, 41, 49], [39, 36, 12, 40], [61, 57, 56, 60], [78, 80, 80, 83]],
    [[46, 43, 42, 51], [41, 37, 38, 42], [59, 59, 55, 58], [81, 78, 82, 80]],
]

Plan your program here, then type it in and press Run.

Do it on the robot
www.bugbotlab.com/learn/a3-1-arrays-records-and-tuples/
The simulator checks it and tells you when it passes. Nothing to install, no account.

Challenges

The array is stored in row-major order, scan by scan. At what position from the start is scans[2][1][3]? Check your answer by flattening the array into a 1D list.

Print the average of each row position across all three scans, so you can see which row of the view is usually nearest.

Write Reading as a tuple instead of a dataclass. What can you no longer do, and when would that be an advantage?

What this lesson is about

Questions 6 marks in all

The task: the depth cube

Challenges