254 lines
9.9 KiB
Python
254 lines
9.9 KiB
Python
# Compute grades using real division, with no integer truncation
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from __future__ import division
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import random
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import logging
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from django.conf import settings
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from models import StudentModuleCache
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from module_render import get_module, get_instance_module
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from xmodule import graders
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from xmodule.course_module import CourseDescriptor
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from xmodule.graders import Score
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from models import StudentModule
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log = logging.getLogger("mitx.courseware")
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def yield_module_descendents(module):
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stack = module.get_display_items()
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while len(stack) > 0:
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next_module = stack.pop()
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stack.extend( next_module.get_display_items() )
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yield next_module
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def grade(student, request, course, student_module_cache=None):
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"""
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This grades a student as quickly as possible. It retuns the
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output from the course grader, augmented with the final letter
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grade. The keys in the output are:
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course: a CourseDescriptor
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- grade : A final letter grade.
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- percent : The final percent for the class (rounded up).
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- section_breakdown : A breakdown of each section that makes
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up the grade. (For display)
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- grade_breakdown : A breakdown of the major components that
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make up the final grade. (For display)
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More information on the format is in the docstring for CourseGrader.
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"""
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grading_context = course.grading_context
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if student_module_cache == None:
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student_module_cache = StudentModuleCache(course.id, student, grading_context['all_descriptors'])
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totaled_scores = {}
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# This next complicated loop is just to collect the totaled_scores, which is
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# passed to the grader
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for section_format, sections in grading_context['graded_sections'].iteritems():
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format_scores = []
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for section in sections:
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section_descriptor = section['section_descriptor']
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section_name = section_descriptor.metadata.get('display_name')
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should_grade_section = False
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# If we haven't seen a single problem in the section, we don't have to grade it at all! We can assume 0%
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for moduledescriptor in section['xmoduledescriptors']:
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if student_module_cache.lookup(
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course.id, moduledescriptor.category, moduledescriptor.location.url()):
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should_grade_section = True
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break
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if should_grade_section:
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scores = []
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# TODO: We need the request to pass into here. If we could forgo that, our arguments
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# would be simpler
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section_module = get_module(student, request,
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section_descriptor.location, student_module_cache,
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course.id)
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if section_module is None:
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# student doesn't have access to this module, or something else
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# went wrong.
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continue
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# TODO: We may be able to speed this up by only getting a list of children IDs from section_module
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# Then, we may not need to instatiate any problems if they are already in the database
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for module in yield_module_descendents(section_module):
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(correct, total) = get_score(course.id, student, module, student_module_cache)
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if correct is None and total is None:
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continue
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if settings.GENERATE_PROFILE_SCORES:
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if total > 1:
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correct = random.randrange(max(total - 2, 1), total + 1)
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else:
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correct = total
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graded = module.metadata.get("graded", False)
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if not total > 0:
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#We simply cannot grade a problem that is 12/0, because we might need it as a percentage
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graded = False
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scores.append(Score(correct, total, graded, module.metadata.get('display_name')))
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section_total, graded_total = graders.aggregate_scores(scores, section_name)
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else:
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section_total = Score(0.0, 1.0, False, section_name)
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graded_total = Score(0.0, 1.0, True, section_name)
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#Add the graded total to totaled_scores
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if graded_total.possible > 0:
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format_scores.append(graded_total)
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else:
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log.exception("Unable to grade a section with a total possible score of zero. " + str(section_descriptor.location))
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totaled_scores[section_format] = format_scores
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grade_summary = course.grader.grade(totaled_scores)
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# We round the grade here, to make sure that the grade is an whole percentage and
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# doesn't get displayed differently than it gets grades
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grade_summary['percent'] = round(grade_summary['percent'] * 100 + 0.05) / 100
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letter_grade = grade_for_percentage(course.grade_cutoffs, grade_summary['percent'])
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grade_summary['grade'] = letter_grade
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return grade_summary
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def grade_for_percentage(grade_cutoffs, percentage):
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"""
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Returns a letter grade 'A' 'B' 'C' or None.
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Arguments
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- grade_cutoffs is a dictionary mapping a grade to the lowest
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possible percentage to earn that grade.
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- percentage is the final percent across all problems in a course
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"""
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letter_grade = None
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for possible_grade in ['A', 'B', 'C']:
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if percentage >= grade_cutoffs[possible_grade]:
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letter_grade = possible_grade
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break
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return letter_grade
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def progress_summary(student, course, grader, student_module_cache):
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"""
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This pulls a summary of all problems in the course.
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Returns
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- courseware_summary is a summary of all sections with problems in the course.
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It is organized as an array of chapters, each containing an array of sections,
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each containing an array of scores. This contains information for graded and
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ungraded problems, and is good for displaying a course summary with due dates,
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etc.
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Arguments:
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student: A User object for the student to grade
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course: An XModule containing the course to grade
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student_module_cache: A StudentModuleCache initialized with all
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instance_modules for the student
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"""
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chapters = []
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# Don't include chapters that aren't displayable (e.g. due to error)
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for c in course.get_display_items():
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# Skip if the chapter is hidden
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hidden = c.metadata.get('hide_from_toc','false')
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if hidden.lower() == 'true':
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continue
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sections = []
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for s in c.get_display_items():
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# Skip if the section is hidden
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hidden = s.metadata.get('hide_from_toc','false')
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if hidden.lower() == 'true':
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continue
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# Same for sections
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graded = s.metadata.get('graded', False)
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scores = []
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for module in yield_module_descendents(s):
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# course is a module, not a descriptor...
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course_id = course.descriptor.id
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(correct, total) = get_score(course_id, student, module, student_module_cache)
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if correct is None and total is None:
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continue
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scores.append(Score(correct, total, graded,
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module.metadata.get('display_name')))
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section_total, graded_total = graders.aggregate_scores(
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scores, s.metadata.get('display_name'))
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format = s.metadata.get('format', "")
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sections.append({
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'display_name': s.display_name,
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'url_name': s.url_name,
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'scores': scores,
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'section_total': section_total,
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'format': format,
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'due': s.metadata.get("due", ""),
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'graded': graded,
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})
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chapters.append({'course': course.display_name,
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'display_name': c.display_name,
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'url_name': c.url_name,
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'sections': sections})
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return chapters
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def get_score(course_id, user, problem, student_module_cache):
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"""
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Return the score for a user on a problem, as a tuple (correct, total).
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user: a Student object
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problem: an XModule
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cache: A StudentModuleCache
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"""
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if not (problem.descriptor.stores_state and problem.descriptor.has_score):
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# These are not problems, and do not have a score
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return (None, None)
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correct = 0.0
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# If the ID is not in the cache, add the item
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instance_module = get_instance_module(course_id, user, problem, student_module_cache)
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# instance_module = student_module_cache.lookup(problem.category, problem.id)
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# if instance_module is None:
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# instance_module = StudentModule(module_type=problem.category,
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# course_id=????,
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# module_state_key=problem.id,
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# student=user,
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# state=None,
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# grade=0,
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# max_grade=problem.max_score(),
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# done='i')
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# cache.append(instance_module)
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# instance_module.save()
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# If this problem is ungraded/ungradable, bail
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if instance_module.max_grade is None:
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return (None, None)
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correct = instance_module.grade if instance_module.grade is not None else 0
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total = instance_module.max_grade
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if correct is not None and total is not None:
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#Now we re-weight the problem, if specified
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weight = getattr(problem, 'weight', None)
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if weight is not None:
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if total == 0:
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log.exception("Cannot reweight a problem with zero weight. Problem: " + str(instance_module))
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return (correct, total)
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correct = correct * weight / total
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total = weight
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return (correct, total)
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