Summary
This postmortem article discusses two Python programs that were written to solve specific problems, but contained errors that led to their failure. The first program was designed to read strings from a file and write to an output file all strings that appear as a substring of at least one other string in the list. The second program was intended to find the subject in which a given student achieved the highest score. Key takeaways from these programs include the importance of handling edge cases and properly testing code.
Root Cause
The root cause of the failures in these programs was:
- Insufficient testing: The programs were not thoroughly tested, leading to unforeseen errors.
- Lack of error handling: The programs did not adequately handle potential errors, such as file not found or invalid input.
- Inadequate algorithm design: The algorithms used in the programs were not efficient or effective, leading to incorrect results.
Why This Happens in Real Systems
These types of errors can occur in real systems due to:
- Complexity: As systems become more complex, it can be difficult to anticipate and test all possible scenarios.
- Time constraints: Developers may be under pressure to meet deadlines, leading to rushed testing and debugging.
- Lack of experience: Junior developers may not have the experience or knowledge to design and test effective algorithms.
Real-World Impact
The impact of these errors can be significant, including:
- Data loss: Incorrectly written data to files can lead to data loss or corruption.
- System crashes: Unhandled errors can cause systems to crash or become unresponsive.
- Security vulnerabilities: Inadequate error handling can create security vulnerabilities that can be exploited by attackers.
Example or Code
# Example of how to read strings from a file and write substrings to an output file
def find_substrings(input_file, output_file):
with open(input_file, 'r') as f:
strings = [line.strip() for line in f.readlines()]
substrings = [s for s in strings if any(s in string for string in strings if s!= string)]
with open(output_file, 'w') as f:
for substring in substrings:
f.write(substring + '\n')
# Example of how to find the subject with the highest score for a given student
import pandas as pd
def highest_score(student_id):
df = pd.read_csv('scores.csv')
student_scores = df[df['student_id'] == student_id]
if student_scores.empty:
return None
max_score = student_scores['score'].max()
subject = student_scores.loc[student_scores['score'] == max_score, 'subject'].iloc[0]
return subject
# Call the function from the main body and print the returned result
print(highest_score(1))How Senior Engineers Fix It
Senior engineers fix these types of errors by:
- Thoroughly testing their code to ensure it works correctly in all scenarios.
- Using debugging tools to identify and fix errors.
- Code reviewing to ensure that code is well-structured and effective.
- Handling errors to prevent system crashes and data loss.
Why Juniors Miss It
Junior developers may miss these errors due to:
- Lack of experience: Junior developers may not have the experience or knowledge to anticipate and fix these types of errors.
- Insufficient training: Junior developers may not have received adequate training in testing, debugging, and error handling.
- Overconfidence: Junior developers may be overconfident in their abilities and not thoroughly test their code. Key concepts to focus on include testing, debugging, and error handling.