Errors

Errors#

At this point of the course, you have undoubtedly encountered many different errors in Python and (hopefully) fixed at the very least most of them. In this notebook, we will look at the most common types of errors you might run into, and some common fixes for these.

It is your job to fix these errors using the techniques you learned in PA1.7 on debugging. You will pass this notebook if you are able to run everything without throwing any errors. Before starting the notebook, please read through this chapter in the book om error types and this page for more information on debugging.

\(\text{Task 4.1:}\)

Fix the errors in the cells below.

Syntax Errors#

The code below has several syntax errors. See if you can fix them! For more details about syntax errors, please refer to the MUDE book.

# This function should take a list of numbers and check if each item is higher than 10 or not
# If it is higher than 10, it should print the value, otherwise it should print "not over 10"
def over_10(input)
    for i in input:
    if number > 10
        print(f"Value: {number")
    else
        print("not over 10')

Name and Scope Errors#

The code below has several name and scope errors.

# The code below is supposed to sum all even numbers in a list and print the last even number processed

total_sum = 0

def sum_even_numbers(numbers):

    print("Starting sum with previous value:", previous_total)

    for n in numbers:
        if n % 2 == 0:
            total_sum += n
            last_even = n
    print("Last even number processed:", last_even)

    return total_sum

nums = [3, 6, 2, 7, 8, 5]
sum_even_numbers(nums)

print("The last even number in the list was:", last_even)

Type and Attribute Errors#

The code below has several Type and Attribute Errors. See if you can fix them.

# The code below is supposed to create a Person object and return it
# It should then print the name of the person, in this case 'John'

class Person:
    def __init__(self, name):
        self.name = name

def create_person():
    Person("John")  

p = create_person()
print(p.name)

File and Import Errors#

The code below has two errors in them. See if you can fix them.

import os
from urllib.request import urlretrieve

def findfile(fname):
    filepath = os.path.join('auxiliary_files', fname)
    if not os.path.isfile(filepath):
        os.makedirs('auxiliary_files', exist_ok=True)
        print(f"Downloading {fname}...")
        urlretrieve('https://github.com/TUDelft-MUDE/source-files/raw/main/file/'+fname, filepath)

findfile('numbers.csv')

# The code below is supposed to read a CSV file using pandas and print its contents

import panddas as pd

file = panda.read_csv('numbers.csv')
print(file)

Index Errors#

See if you can identify and fix the index errors in the code below.

# This code is supposed to create a 5x5 matrix with 5s on the diagonal and 1s just above the diagonal

import numpy as np

A = np.zeros((5, 5))
np.fill_diagonal(A, 5)
A[range(3), range(1, 5)] = 1

A mixed bag#

As you probably know by now, errors also rarely exist in isolation. Usually, you get a bundle of them that you need to fix one after another. Below is a snippet of code that have several errors of different types in them. See if you can fix the code!

import numpy as n

# This code is supposed to create two arrays, a and b and then sum them element-wise
a = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
b = np.linspace(0, 10, 11)

for i in range(0, a.size):
    a[i] = a[i] +a[i-1]

c = a+b
print(c)

Logical Errors#

Logical errors are usually the most difficult errors to deal with as the code will still run without any errors and you do not get any hints on what is wrong. This PA includes a .py files with code that contains logical errors: max_square_even.py. Try using the Python debugger for these, as then you can see how the variables change step-by-step!

\(\text{Task 4.2:}\)

Fix the errors in the .py file.

By Jialei Ding and Robert Lanzafame, Delft University of Technology. CC BY 4.0, more info on the Credits page of Workbook.

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