Functions - Answer Key

Authors

Noor Sohail

Will Gammerdinger

Published

March 14, 2026

Exercise 1

Round the num variable to 2 decimal places using the round() function.

num = 3.14159
rounded_num = round(num, 2)
print(rounded_num)

3.14

What happens when you specify a negative value for the ndigits argument in the round() function? Try it out and explain the output.

rounded_num = round(num, -1)
print(rounded_num)

0.0

When you specify a negative value for the ndigits argument in the round() function, it rounds the number to the left of the decimal point. In this case, we are rounding to the nearest 10, so 3.14159 gets rounded to 0.0.

What happens if you apply the round() function to the numbers list? Try it out and explain the output.

numbers = [2, 2.23, 0.77, 10, 40.2]
rounded_numbers = round(numbers)

TypeError: type list doesn't define __round__ method

print(rounded_numbers)

NameError: name 'rounded_numbers' is not defined

We get an error, because the round() function is not designed to work with lists. It expects a single number as input. To round each number in the list, we would need to apply the round() function to each element individually, perhaps using a loop or a list comprehension.

Apply the sorted() function to the numbers list. What does it do? What are the arguments for the sorted() function? Use the help() function to find out.

help(sorted)

Help on built-in function sorted in module builtins:

sorted(iterable, /, *, key=None, reverse=False)
    Return a new list containing all items from the iterable in ascending order.
    
    A custom key function can be supplied to customize the sort order, and the
    reverse flag can be set to request the result in descending order.

The default value for the argument reverse is False, which means that the sorted() function will sort the numbers in ascending order by default.

sorted_numbers = sorted(numbers)
print(sorted_numbers)

[0.77, 2, 2.23, 10, 40.2]

If we set reverse=True, it will sort the numbers in descending order.

sorted_numbers = sorted(numbers, reverse=True)
print(sorted_numbers)

[40.2, 10, 2.23, 2, 0.77]

Exercise 2

Write a function called multiply_it, which takes two inputs: a numeric value x, and a numeric value y. The function will return the product of these two numeric values, which is x * y.

For example, multiply_it(x=4, y=6) will return output 24.

def multiply_it(x, y):
    return x * y 

# Example x = 4, y = 6
result = multiply_it(x=4, y=6)
print(result)

Exercise 3

Custom Functions - Create a function temp_conv(), which converts the temperature in Fahrenheit (input) to the temperature in Kelvin (output). Let’s perform a two-step calculation:

first convert from Fahrenheit to Celsius, then
convert from Celsius to Kelvin

# The formula for celsius to farenheight: 
temp_c = (temp_f - 32) * 5 / 9

# The formula for celsius to kelvin
temp_k = temp_c + 273.15

def temp_conv(temp_f):
    temp_c = (temp_f - 32) * 5 / 9
    temp_k = temp_c + 273.15
    return temp_k

Test your function. If your input is 70, the result of temp_conv(70) should be 294.2611.

result = temp_conv(70)
print(result)

294.26111111111106

Nesting Functions - Now we want to round the temperature in Kelvin (output of temp_conv()) to a single decimal place. Use the round() function with the newly-created temp_conv() function to achieve this in one line of code.

round(temp_conv(70), 1)

294.3

If your input is 70, the output should now be 294.3.

Reuse

CC-BY-4.0

--- title: "Functions - Answer Key" author: - Noor Sohail - Will Gammerdinger date: "2026-03-14" license: "CC-BY-4.0" editor_options: markdown: wrap: 72 --- ```{r} #| label: load_libraries_data #| echo: false # Load libraries and data ``` # Exercise 1 1. Round the `num` variable to 2 decimal places using the `round()` function. ```{python} #| label: exercise_1 num = 3.14159 rounded_num = round(num, 2) print(rounded_num) ``` 2. What happens when you specify a negative value for the `ndigits` argument in the `round()` function? Try it out and explain the output. ```{python} #| label: exercise_2 rounded_num = round(num, -1) print(rounded_num) ``` When you specify a negative value for the `ndigits` argument in the `round()` function, it rounds the number to the left of the decimal point. In this case, we are rounding to the nearest 10, so 3.14159 gets rounded to 0.0. 3. What happens if you apply the `round()` function to the `numbers` list? Try it out and explain the output. ```{python} #| label: exercise_3 #| error: true numbers = [2, 2.23, 0.77, 10, 40.2] rounded_numbers = round(numbers) print(rounded_numbers) ``` We get an error, because the `round()` function is not designed to work with lists. It expects a single number as input. To round each number in the list, we would need to apply the `round()` function to each element individually, perhaps using a loop or a list comprehension. 4. Apply the `sorted()` function to the `numbers` list. What does it do? What are the arguments for the `sorted()` function? Use the `help()` function to find out. ```{python} #| label: sorted_help help(sorted) ``` The default value for the argument `reverse` is `False`, which means that the `sorted()` function will sort the numbers in ascending order by default. ```{python} #| label: exercise_4_sorted sorted_numbers = sorted(numbers) print(sorted_numbers) ``` If we set `reverse=True`, it will sort the numbers in descending order. ```{python} #| label: exercise_4_sorted_rev sorted_numbers = sorted(numbers, reverse=True) print(sorted_numbers) ``` # Exercise 2 5. Write a function called `multiply_it`, which takes two inputs: a numeric value ``x``, and a numeric value y. The function will return the product of these two numeric values, which is `x * y`. For example, `multiply_it(x=4, y=6)` will return output `24`. ```{python} #| label: exercise_5 def multiply_it(x, y): return x * y # Example x = 4, y = 6 result = multiply_it(x=4, y=6) print(result) ``` # Exercise 3 6. **Custom Functions** - Create a function `temp_conv()`, which converts the temperature in Fahrenheit (input) to the temperature in Kelvin (output). Let’s perform a two-step calculation: - first convert from Fahrenheit to Celsius, then - convert from Celsius to Kelvin ```{python} #| label: temp_conv_equation #| eval: false # The formula for celsius to farenheight: temp_c = (temp_f - 32) * 5 / 9 # The formula for celsius to kelvin temp_k = temp_c + 273.15 ``` ```{python} #| label: temp_conv def temp_conv(temp_f): temp_c = (temp_f - 32) * 5 / 9 temp_k = temp_c + 273.15 return temp_k ``` Test your function. If your input is 70, the result of `temp_conv(70)` should be 294.2611. ```{python} #| label: temp_conv_test result = temp_conv(70) print(result) ``` 7. **Nesting Functions** - Now we want to round the temperature in Kelvin (output of `temp_conv()`) to a single decimal place. Use the `round()` function with the newly-created `temp_conv()` function to achieve this in one line of code. ```{python} #| label: temp_conv_rounded round(temp_conv(70), 1) ``` If your input is 70, the output should now be 294.3.