Assignment 03#

Due date: 29.03.2023

Important

This week’s assignment has to be returned in the form of one (1) python script OR one (1) jupyter notebook. Don’t forget the instructions!

  • Exercise 1 and Exercise 2 are independent from one another.

  • Exercise 3 uses the functions you wrote in Exercise 1 and 2 in a small program.

Exercise 1: write two temperature conversion functions#

Write a function called fahrenheit_to_celsius, which accepts a float or int as input parameter and returns the temperature value converted to degrees celsius. Here are some examples of the function’s execution:

print(fahrenheit_to_celsius(100))
37.77777777777778

print(fahrenheit_to_celsius(68))
20.0

Now, write a second function called celsius_to_fahrenheit, which does the opposite. Here are some examples:

print(celsius_to_fahrenheit(38))
100.4

print(celsius_to_fahrenheit(0))
32.0

Important

A few things to note here:

  • these functions are fruitful functions: they returns a value

  • these functions do not print anything: there is no print statement in these functions

  • these functions have one input parameter only

If you are unsure about what I mean with “fruitful” or “input parameter”, go back to the lecture notes.

Exercise 2: write two user input checking functions#

Write a new function with the following signature:

def valid_temperature_input(min_value):
    <your code here>
    return number

This function uses python’s input to ask for the temperature value to convert, and then decides:

  • if the value can be converted to a number and this number is above the parameter min_value, return this number

  • if the value cannot be converted to a number or is below the specified limit print a message to the user and ask them to enter a new value.

  • this program never ends until a valid value is entered.

Examples:

print(valid_temperature_input(0))
Please enter a temperature value: 10
10.0

print(valid_temperature_input(0))
Please enter a temperature value: ups
This value is not valid! Try again.
Please enter a temperature value: -2
This value is below the specified limit! Try again.
Please enter a temperature value: 12.3
12.3

Now, write a second input function with the following signature:

def valid_conversion_input():
    <your code here>
    return number

This function asks the user what kind of conversion they want to do, and validates the input (if needed, asking again if the value is not correct). Examples:

print(valid_conversion_input())
What conversion do you want to do? Type:
1 for Celsius to Farenheit
2 for Farenheit to Celsius
3 for doing nothing
Your input: 1
1

print(valid_conversion_input())
What conversion do you want to do? Type:
1 for Celsius to Farenheit
2 for Farenheit to Celsius
3 for doing nothing
Your input: 3
3

print(valid_conversion_input())
What conversion do you want to do? Type:
1 for Celsius to Farenheit
2 for Farenheit to Celsius
3 for doing nothing
Your input: ups
Not valid! Try again.
Your input: 4
Not valid! Try again.
Your input: 2
2

The function always returns one of 1, 2, 3 and never ends until the user gives a valid input.

Important

A few things to note here:

  • these functions are fruitful functions: they returns a value

  • these functions do print something: there are print statements in these functions

  • these functions have no input parameter.

  • these functions use input() internally.

If you are unsure about what I mean with “fruitful” or “input parameter”, go back to the lecture notes.

Exercise 3: write a temperature conversion program#

Now, rely on your hard work and the functions you just created to write a full program (in a python file or a notebook). The program:

  • asks the user what they want to do (convert or do nothing)

  • if convert, ask the user for the value to convert. The minimum acceptable value depends on the conversion function to use (indeed, the value in °C or °F cannot be below the absolute minimum, 0 Kelvin)

  • convert the value to the other unit and print it on screen

This program should use the functions you wrote in exercise 1 and 2, and therefore have only little code other than calling the functions.

Example output for a °C to °F conversion:

0°C are converted to 32.0°F

Exercise 4 (optional): design a test function#

In addition to your program, write a function called test_conversion() with no arguments, and no output (a void function in the book).

When run, this function checks that some given values are converted properly. You can pick a few examples from this table here. If the value is not the expected one, print a message saying that there is a problem.

Furthermore, the function should check that for 10 random numbers selected between 0 and 100, the following test is True:

value = 89.2  # or any random number
output = celsius_to_fahrenheit(fahrenheit_to_celsius(value))
value == output  # Should be true

Important: if you run these tests often enough, you will see that they do not always pass!!! Actually, they fail quite often. Don’t panic and accept it: the reason for this problem (and how to overcome it) will be explained later.