no such item for cursor instance

ghz 9months ago ⋅ 144 views

This is the code I used to retrieve data from two different collections and matched them on the department criteria. However after running the function for 7 times, I get an index Error of "no such item for cursor instance"

def update_instructor_course(college,department,department_course_list):
    get_department_courses = (courses.find({"college": college, "department": department}))
    get_department_instructors = (employees.find({"college":college, "department": department}))[:len(department_course_list)]

    for index, instructor in enumerate(get_department_instructors):
        employees.update_one({"_id": ObjectId(instructor["_id"])},{"$set": {"course": [get_department_courses[index]['course_code']]}})
        courses.update_one({"_id":ObjectId(get_department_courses[index]["_id"])}, {"$set":{"instructor":instructor['employee_id']}})```

Answers

The error "no such item for cursor instance" indicates that you're trying to access an item from the cursor beyond its available items. This can happen if the length of department_course_list is less than the number of items returned by the get_department_instructors cursor.

Here's the modified code to handle this issue:

def update_instructor_course(college, department, department_course_list):
    # Fetch courses and instructors cursors
    get_department_courses = courses.find({"college": college, "department": department})
    get_department_instructors = employees.find({"college": college, "department": department})

    # Iterate over both cursors
    for index, instructor in enumerate(get_department_instructors):
        # Fetch the course only if it exists in the department_course_list
        if index < len(department_course_list):
            course_code = department_course_list[index]['course_code']
            # Update instructor with course
            employees.update_one({"_id": instructor["_id"]}, {"$set": {"course": [course_code]}})
            # Update course with instructor
            courses.update_one({"_id": department_course_list[index]["_id"]}, {"$set": {"instructor": instructor['employee_id']}})
        else:
            # If department_course_list is smaller than the number of instructors, break the loop
            break

In this modified version:

  1. We iterate over both get_department_instructors and department_course_list simultaneously using enumerate to avoid index errors.
  2. Inside the loop, we check if the index is within the length of department_course_list before accessing its items.
  3. If the index exceeds the length of department_course_list, we break the loop to avoid trying to access nonexistent items.

This modification should prevent the "no such item for cursor instance" error and ensure that the loop terminates gracefully when there are no more items to process.

#mongodb