Paper 2: Application of computational thinking (practice version)

The code below should print the average of the scores but contains errors.

def average(values):    total = 0    for i in range(1, len(values)):        total = total + values[i]    return total / len(values) scores = [12, 15, 9, 20]print("Average is " + average(scores))

Identify and correct three errors.

Using the data below, write a function clean(readings) that returns a new list without the -999 values, and a function stats(values) that returns the minimum, maximum and mean (rounded to 1 d.p.).

readings = [18.5, 19.2, 21.0, -999, 22.4, 23.1, 20.7, -999, 19.8, 18.9]# -999 means the sensor failed to record a value

Write a program that repeatedly asks a user to enter temperature readings (or 'done' to finish), validates each one (must be a number between −50 and 60), stores valid readings, and then outputs: the number of readings, the mean, and how many readings were above the mean. Use at least two functions.

Extend your program so that the valid readings are saved to a text file, one per line, and can be loaded again when the program next starts.

Without using built-in sort functions, write a function that sorts a list of readings into ascending order using insertion sort, and a function that uses binary search to report whether a given reading is in the sorted list.

Write a recursive function that returns the sum of the digits of a positive integer (e.g. 4071 → 12) and explain how the base case prevents infinite recursion.

Implement a stack class in Python with push, pop and peek methods and an isEmpty method. pop and peek must handle an empty stack sensibly. Use it to check whether the brackets in a string such as '(a[b]{c})' are balanced.

Evaluate the efficiency of your solutions to Questions 3 and 5. Suggest how they could be improved for a data set of 10 million readings.