Exercise 2 - Short failing examples

Here we give a series of short functions that are failing for a variety of reasons. Please look over each of these in turn, and try to identify and fix the problem.

Exercise 2A - Nothing being printed??

In this code we have written a function to take two inputs a and b and compute (a + b) / (a - b + 0.01)**2. However, when we try to use it nothing is printed. Please fix this!

def some_expression(a, b):
    output = (a + b)/(a - b + 0.01)**2


my_fav_a = 6
my_least_fav_b = 3

print(some_expression(my_fav_a, my_least_fav_b))

None

Exercise 2B - TypeError??

We have written a function to concatenate two strings. We then provide two strings, but the code says TypeError. Please make it add my strings together!!

def string_contatenator(string1, string2):
    output = string1 + string2
    return output

string1 = "I think I'm ok"
string2 = ["I feel trapped"]

print(string_contatenator(string1, string2))

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
Input In [2], in <module>
      5 string1 = "I think I'm ok"
      6 string2 = ["I feel trapped"]
----> 8 print(string_contatenator(string1, string2))

Input In [2], in string_contatenator(string1, string2)
      1 def string_contatenator(string1, string2):
----> 2     output = string1 + string2
      3     return output

TypeError: can only concatenate str (not "list") to str

Exercise 2C - Assignment and logical equality

Here is a function for determining whether you have a good amount of flour, sugar and eggs to make a cake. Except it doesn’t work. Please fix it!

def baking_cake(amount_flour, sugar_spoons, num_eggs):
    if amount_flour = 5:
        return f"Are you sure that you want to use {amount_flout} kg of flour to bake a cake?"
    elif amount_flout < 0.25 and sugar_spoons = 20:
        return f"This is going to be very sugary"
    else:
        return f"This looks good for making a cake, but maybe check with Mary Berry."

amount_flour = 4
sugar_spoons == 5
num_eggs = 2
print(f"Adding first number {first_num} to the second number {sec_num} gives me {first_num + sec_num}")

  Input In [3]
    if amount_flour = 5:
                    ^
SyntaxError: invalid syntax

Exercise 2D - N factorial always equals 1??

We wish to calculate a factorial of \(n\), in maths we often denote this as \(n!\) it is defined as $\( n! = 1 \cdot 2 \cdot 3 \cdot 4 \cdot \cdots \cdot n\)$

We have written a code to do this …. except whatever we give it as input it always returns 1. Please fix my code!

def my_func(n):
    total = 1.0
    for k in range(1, n+1):
        total *= k
        return total

print(my_func(3), my_func(5), my_func(7))

1.0 1.0 1.0

Exercise 2E - List is not callable??

We have a function that takes a list and returns the last 2 elements as a new list. Except it fails with the strange error seen below. Please fix!

def last_but_one_and_last(my_list):
    if len(my_list)>=2:
        output = [my_list(-2), my_list[-1]]
        return output

my_list = [1, 2, 3, 4]
print(last_but_one_and_last(my_list))

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
Input In [5], in <module>
      4         return output
      6 my_list = [1, 2, 3, 4]
----> 7 print(last_but_one_and_last(my_list))

Input In [5], in last_but_one_and_last(my_list)
      1 def last_but_one_and_last(my_list):
      2     if len(my_list)>=2:
----> 3         output = [my_list(-2), my_list[-1]]
      4         return output

TypeError: 'list' object is not callable

Exercise 2F - Function just gives the wrong output??

After being upset that none of my 5 short code snippets above worked, I tried to reassure myself by coding something quick. A function that takes one input and returns the number squared. However, the function just seems to return random numbers? HEEEELLLPPP!!!!

def my_fonc(my_fav_n):
    return my_fav_a**2

print(my_func(2))

1.0