Run multiple python codes and Check with answer data

Question

I wrote the code for my undergraduate TA jobs, to check assignment codes of students in Python class are correct or not.

Usage of the code is

$ python [test01.py[,test02 , ...] answer.dat grade.md

It will write grades (range 0~100) to a file called grade.md.

"""
Testing Assginments
by kidkkr
03-16-2017
"""
import os
import sys
from difflib import SequenceMatcher
class ResultChecker:
 """ Check python code result with answer data """
 __slots__ = '_srcFiles', '_ansFile', '_gradeFile', '_grade', '_ans'
 def __init__(self, srcFiles, ansFile, gradeFile):
 self._srcFiles = srcFiles 
 self._ansFile = ansFile 
 self._ans = open(self._ansFile, 'r').read()
 self._gradeFile = gradeFile
 self._grade = "# Grade File\n"
 def _run_code(self, src):
 print('-----------running ' + src + '..-----------')
 os.system('python ' + src + ' > result.swp')
 res = open('./result.swp', 'r').read()
 ratio = int(SequenceMatcher(None, res, self._ans).ratio() * 100)
 self._grade += src + ' ' + str(ratio) + '\n'
 print('result: ' + str(ratio))
 def check(self):
 for src in self._srcFiles:
 self._run_code(src)
 open(self._gradeFile, 'w').write(self._grade) # Write _grade to a file
 print('Checking has completed.')
 print(self._gradeFile + ":")
 print(self._grade)
def __main__():
 if len(sys.argv) < 2: # Check arguments
 raise ValueError('')
 srcFiles = sys.argv[1:-2]
 ansFile = sys.argv[-2]
 gradeFile = sys.argv[-1]
 ResultChecker(srcFiles, ansFile, gradeFile).check()
if __name__ == '__main__':
 __main__() 

• Adam Martin: Note that you should make sure you're being safe with untrusted scripts. Even if they're not malicious a student could break things that could cause future tests to fail or bigger problems. You should sandbox each run, either using something from here wiki.python.org/moin/Asking%20for%20Help/… or simply using a vm
• kidkkr: I could not reached to that. It will be possible because I run codes directly in my shell.. Thank you for the advice!

Answer 1

Here is something I would improve:

• fix the variable naming - according to PEP8, use lower case and separate words with an underscore - e.g. _grade_file instead of _gradeFile

• use argparse module instead of manually reading from sys.argv - you will get the auto-generated command-line help for free and it is generally more readable, structured and scalable. As a bonus, you may avoid checking the length of the sys.argv and reading the "files" into variables. Something along these lines:

  import argparse
  def parse_arguments():
   parser = argparse.ArgumentParser()
   parser.add_argument('--source-files', nargs="+", type=str)
   parser.add_argument('--answer-file', type=argparse.FileType('r'))
   parser.add_argument('--grade-file', type=argparse.FileType('w'))
   return parser.parse_args()
  

  Note the use of the special FileType argument type.

  And, because of the use of nargs="+", you should change the way you pass python file names - instead of a comma-separated list, use space:

  $ python --source-files test01.py test02.py --answer-file answer.dat --grade-file grade.md
  

• use with context manager when opening files

• try subprocess.Popen() instead of os.system() - with "popen" you may not need to temporarily write the result to a swap file and read the standard out and error directly
• I understand that an underscore at the beginning of a variable name is a convention to mark "private variables", but, if the checker class would not be a part of a public-facing API, it would be okay to remove the underscores to improve on readability

• kidkkr: argparse module is cool. I hope I used to PEP8.. Thank you :)