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Python TypeError · Exercises
Core Python

Python TypeError Exercises

4 exercises that build on the Python TypeError: What It Means and How to Fix It lesson, from easy to hard. Each one is checked in your browser when you press Check. Stuck? Use the hint before peeking at the solution.

What this lesson covers: A TypeError means Python was asked to do something with a value whose type doesn't support it, such as adding a number to text or calling something that isn't a function. By the end you can read a TypeError message and its traceback, recognise the five most common causes and fix each one. You will practise: Fix the score message; Predict the mixed total; Add up mixed prices; Two TypeErrors in one function.

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1. Fix the score message

Fix the bug Easy

This code should store "Your score is 87 points" in message and print it, but it raises a TypeError. Fix it without changing the value of score.

Your code 
score = 87
message = "Your score is " + score + " points"
print(message)




  
  

  
  
  



    
  
    

  

    
2. Predict the mixed total

    Predict the output
    Easy
    
  

  
Read the code and type exactly what it will print. Then press Check to compare.

  
    

  

    Read this code
    

      
      
    

  

  
values = [10, "5", 2.5]
total = 0

for v in values:
    try:
        total = total + v
        print("added", v)
    except TypeError:
        print("skipped", repr(v))

print(total)

  
  
  

  

    
      
      
      
      
    
    
  

  




  
  

  
  
  



    

  
    

  

    
3. Add up mixed prices

    Write code
    Medium
    
  

  
Prices arrive from a form as a mix of strings and numbers, e.g. ["2.50", 3, "4"]. Change total_cost(prices) so it converts every price to a float before adding, and returns the total rounded to 2 decimal places. An empty list should give 0.

  
    

  

    Your code
    

      
      
      
      
    

  

  
def total_cost(prices):
    return sum(prices)

print(total_cost(["2.50", 3, "4"]))

  
  
  
  

    
      
      
      
      
    
    
  

  




  
  

  
  
  



    
  
    

  

    
4. Two TypeErrors in one function

    Fix the bug
    Hard
    
  

  
count_points(points) should count how often each [x, y] point appears and return a dictionary whose keys are (x, y) tuples, e.g. {(1, 2): 2, (3, 4): 1}. There are two separate TypeErrors hiding here: fix the first, run again, then fix the second.

  
    

  

    Your code
    

      
      
      
      
    

  

  
def count_points(points):
    counts = {}
    for point in points:
        counts[point] = counts.get(point, 0) + 1

result = count_points([[1, 2], [3, 4], [1, 2]])
print(result[(1, 2)])

  
  
  
  

    
      
      
      
      
    
    
  

  




  
  

  
  
  



    
  
  

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