grading.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-
import json

import requests


class Grader(object):
    def __init__(self, assignment_key, all_parts=()):
        """
        Assignment key is the way to tell Coursera which problem is being submitted.
        """
        self.submission_page = \
            'https://hub.coursera-apps.org/api/onDemandProgrammingScriptSubmissions.v1'
        self.assignment_key = assignment_key
        self.answers = {part: None for part in all_parts}

    def submit(self, email, token):
        submission = {
            "assignmentKey": self.assignment_key,
            "submitterEmail": email,
            "secret": token,
            "parts": {}
        }
        for part, output in self.answers.items():
            if output is not None:
                submission["parts"][part] = {"output": output}
            else:
                submission["parts"][part] = dict()
        response = requests.post(self.submission_page, data=json.dumps(submission))
        if response.status_code == 201:
            print('Submitted to Coursera platform. See results on assignment page!')
        else:
            d = response.json()
            if d is not None and u'details' in d and u'learnerMessage' in d[u'details']:
                print(d[u'details'][u'learnerMessage'])
                print("Hint: try generating new token and make sure you spelled it correctly")
            else:
                print("Unknown response from Coursera: {}".format(response.status_code))
                print(d)

    def set_answer(self, part, answer):
        """Adds an answer for submission. Answer is expected either as string, number, or
           an iterable of numbers.
           Args:
              part - str, assignment part id
              answer - answer to submit. If non iterable, appends repr(answer). If string,
                is appended as provided. If an iterable and not string, converted to
                space-delimited repr() of members.
        """
        if isinstance(answer, str):
            self.answers[part] = answer
        else:
            try:
                self.answers[part] = " ".join(map(repr, answer))
            except TypeError:
                self.answers[part] = repr(answer)


def array_to_grader(array, epsilon=1e-4):
    """Utility function to help preparing Coursera grading conditions descriptions.
    Args:
       array: iterable of numbers, the correct answers
       epslion: the generated expression will accept the answers with this absolute difference with
         provided values
    Returns:
       String. A Coursera grader expression that checks whether the user submission is in
         (array - epsilon, array + epsilon)"""
    res = []
    for element in array:
        if isinstance(element, int):
            res.append("[{0}, {0}]".format(element))
        else:
            res.append("({0}, {1})".format(element - epsilon, element + epsilon))
    return " ".join(res)