INTRODUCTION – Troubleshooting Concepts

PRACTICE QUIZ: INTRODUCTION TO DEBUGGING

1. What is part of the final step when problem solving?

2. Which tool can you use when debugging to look at library calls made by the software?

3. What is the first step of problem solving?

4. What software tools are used to analyze network traffic to isolate problems? (Check all that apply)

5. The strace (in Linux) tool allows us to see all of the _____ our program has made.

6. What is the general description of debugging?  

7. What is the second step of problem solving?  

8. Which command can you use to scroll through a lot of text output after tracing system calls of a script?  

PRACTICE QUIZ: UNDERSTANDING THE PROBLEM

1. When a user reports that an “application doesn’t work,” what is an appropriate follow-up question to gather more information about the problem?

2. What is a heisenbug?

3. How do we verify if a problem is still persisting or not?

4. The datetime module supplies classes for manipulating dates and times, and contains many types, objects, and methods. You’ve seen some of them used in the dow function, which returns the day of the week for a specific date. We’ll use them again in the next_date function, which takes the date_string parameter in the format of “year-month-day”, and uses the add_year function to calculate the next year that this date will occur (it’s 4 years later for the 29th of February during Leap Year, and 1 year later for all other dates). Then it returns the value in the same format as it receives the date: “year-month-day”.

Can you find the error in the code? Is it in the next_date function or the add_year function? How can you determine if the add_year function returns what it’s supposed to? Add debug lines as necessary to find the problems, then fix the code to work as indicated above. 

import datetime
from datetime import date


def add_year(date_obj):
    try:
        new_date_obj = date_obj.replace(year=date_obj.year + 1)
    except ValueError:
        # This gets executed when the above method fails,
        # which means that we're making a Leap Year calculation
        new_date_obj = date_obj.replace(year=date_obj.year + 4)
    return new_date_obj


def next_date(date_string):
    # Convert the argument from string to date object
    date_obj = datetime.datetime.strptime(date_string, "%Y-%m-%d")
    next_date_obj = add_year(date_obj)


    # Convert the datetime object to string,
    # in the format of "yyyy-mm-dd"
    next_date_string = next_date_obj.strftime("%Y-%m-%d")
    return next_date_string


today = date.today()  # Get today's date
print(next_date(str(today)))
# Should return a year from today, unless today is Leap Day


print(next_date("2021-01-01"))  # Should return 2022-01-01
print(next_date("2020-02-29"))  # Should return 2024-02-29

5. When a user reports that a “website doesn’t work,” what is an appropriate follow-up question you can use to gather more information about the problem?  

6. A program fails with an error, “No such file or directory.” You create a directory at the expected file path and the program successfully runs. Describe the reproduction case you’ll submit to the program developer to verify and fix this error.  

7. Generally, understanding the root cause is essential for _____?  

8. What sort of software bug might we be dealing with if power cycling resolves a problem?  

PRACTICE QUIZ: BINARY SEARCHING A PROBLEM

1. You have a list of computers that a script connects to in order to gather SNMP traffic and calculate an average for a set of metrics. The script is now failing, and you do not know which remote computer is the problem. How would you troubleshoot this issue using the bisecting methodology?

2. When trying to find an error in a log file or output to the screen, what command can we use to review, say, the first 10 lines?

3. The best_search function compares linear_search and binary_search functions to locate a key in the list, returns how many steps each method took, and which method is the best for that situation. The list does not need to be sorted, as the binary_search function sorts it before proceeding (and uses one step to do so). Here, linear_search and binary_search functions both return the number of steps that it took to either locate the key or determine that it’s not in the list. If the number of steps is the same for both methods (including the extra step for sorting in binary_search), then the result is a tie. Fill in the blanks to make this work.

def linear_search(list, key):
   #Returns the number of steps to determine if key is in the list


   #Initialize the counter of steps
   steps=0
   for i, item in enumerate(list):
       steps += 1
       if item == key:
           break
   return ___


def binary_search(list, key):
   #Returns the number of steps to determine if key is in the list


   #List must be sorted:
   list.sort()


   #The Sort was 1 step, so initialize the counter of steps to 1
   steps=1


   left = 0
   right = len(list) - 1
   while left <= right:
       steps += 1
       middle = (left + right) // 2
      
       if list[middle] == key:
           break
       if list[middle] > key:
           right = middle - 1
       if list[middle] < key:
           left = middle + 1
   return ___


def best_search(list, key):
   steps_linear = ___
   steps_binary = ___
   results = "Linear: " + str(steps_linear) + " steps, "
   results += "Binary: " + str(steps_binary) + " steps. "
   if (___):
       results += "Best Search is Linear."
   elif (___):
       results += "Best Search is Binary."
   else:
       results += "Result is a Tie."


   return results


print(best_search([1, 2, 3, 4, 5, 6, 7, 8, 9, 10], 1))
#Should be: Linear: 1 steps, Binary: 4 steps. Best Search is Linear.


print(best_search([10, 2, 9, 1, 7, 5, 3, 4, 6, 8], 1))
#Should be: Linear: 4 steps, Binary: 4 steps. Result is a Tie.


print(best_search([10, 9, 8, 7, 6, 5, 4, 3, 2, 1], 7))
#Should be: Linear: 4 steps, Binary: 5 steps. Best Search is Linear.


print(best_search([1, 3, 5, 7, 9, 10, 2, 4, 6, 8], 10))
#Should be: Linear: 6 steps, Binary: 5 steps. Best Search is Binary.


print(best_search([5, 1, 8, 2, 4, 10, 7, 6, 3, 9], 11))
#Should be: Linear: 10 steps, Binary: 5 steps. Best Search is Binary.

4. When searching for more than one element in a list, which of the following actions should you perform first in order to search the list as quickly as possible?  

5. When troubleshooting an XML configuration file that’s failed after being updated for an application, what would you bisect in the code?  

DEBUG PYTHON SCRIPTS

1. How does debugging a script contribute to the quality and reliability of code and applications?

2. In the lab, what was identified as the root cause of the issue that led to the TypeError?

3. Why is it necessary to convert the integer variable number to a string using the str() function in the revised print statement?

4. In the lab, what is the main issue with the script involving concatenating two different data points?

5. You receive the following error message (TypeError: Can’t convert ‘int’ object to str implicitly). What do you need to do to resolve this error? 

6. In the lab, you encountered an error message that indicates a problem with concatenating a string and an integer. To figure out the root cause of this bug, what step did you take next in the lab after successfully reproducing the error?

7. A recurring problem can be defined as what? 

8. Which of the following best describes the importance of debugging a script? 

9. In the lab, where was the root cause of the issue located? 

10. In the debugging process described, what is the purpose of replacing the original print statement with the following statement?

print("hello " + name + ", your random number is " + str(number))

11. In the lab, what is the main issue with the script involving concatenating two different data points?

12. In the lab, what was the recommended solution to address the issue in the Python script where two different data types (string and int) need to be concatenated?

13. Why is it necessary to convert the integer variable number to a string using the str() function in the revised print statement?

14. Question: In Python, what issue arises when trying to concatenate two different data types, such as a string and an integer, as seen in the provided code snippet?

15. Complete this sentence. In troubleshooting and debugging, a(n) ______________ type of problem is reproducible under the same set of conditions. 

16. When a bug is found in a software program during testing, what is the best way to communicate it to the right individuals(s)? 

17. What can you infer if a recurring problem goes away when you change the system settings? 

18. Why is it important to reproduce an error when debugging scripts? Select all that apply.

19. Which of the following statements are true about adding two different data types directly in Python? 

20. While following the lab instructions and attempting to connect to your VM or run a script, you encounter the error mentioned in the lab: “TypeError: Can’t convert ‘int’ object to str implicitly.” What should be your initial response to address this error?

21. When a bug is found in a software program during testing, what should you do? 

22. Complete this sentence. The error message TypeError: Can’t convert ‘int’ object to str implicitly lets you know that ___________________________. 

23. As part of your testing process, you’ve successfully reproduced the error in the laB: After identifying that the root cause of the issue is a concatenation problem involving different data types (string and integer), you decide to use the str() function to convert the integer variable into a string. How does this step contribute to effective software testing?

24. What is the definition of a recurring problem in the context of troubleshooting and debugging? 

CONCLUSION – Troubleshooting Concepts