get() for single objects in Django - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to get a single Book object by its id.

Django

book = Book.objects.[1](id=5)

Drag options to blanks, or click blank then click option'

Aget

Bfilter

Call

Dexclude

Attempts:

3 left

💡 Hint

Common Mistakes

Using filter() instead of get(), which returns a queryset, not a single object.

Using all() which returns all objects, not filtered by id.

The get() method returns a single object matching the query. Here, it fetches the Book with id=5.

2fill in blank

medium

Complete the code to get a User object by username.

Django

user = User.objects.[1](username='alice')

Drag options to blanks, or click blank then click option'

Aget

Ball

Cexclude

Dfilter

Attempts:

3 left

💡 Hint

Common Mistakes

Using filter() which returns a queryset, not a single object.

Using all() which returns all users.

get() fetches a single User object with the username 'alice'.

3fill in blank

hard

Fix the error in the code to get a Product by its sku.

Django

product = Product.objects.[1](sku='12345')

Drag options to blanks, or click blank then click option'

Aexclude

Bfilter

Call

Dget

Attempts:

3 left

💡 Hint

Common Mistakes

Using filter() and then trying to access attributes directly without indexing.

Using all() which returns all products.

Using get() is correct to fetch a single Product by sku. Using filter() returns a queryset, which may cause errors if you expect a single object.

4fill in blank

hard

Fill both blanks to get a Customer by email and handle the case if not found.

Django

try:
    customer = Customer.objects.[1](email=[2])
except Customer.DoesNotExist:
    customer = None

Drag options to blanks, or click blank then click option'

Aget

B'[e-mail]'

C'[e-mail]'

Dfilter

Attempts:

3 left

💡 Hint

Common Mistakes

Using filter() which returns a queryset, not a single object.

Not quoting the email string.

get() fetches the single Customer with the given email. The email string must be quoted. The exception handles the case when no customer is found.

5fill in blank

hard

Fill all three blanks to get an Order by order_id, check if it exists, and assign None if not.

Django

try:
    order = Order.objects.[1]([2]=[3])
except Order.DoesNotExist:
    order = None

Drag options to blanks, or click blank then click option'

Aget

Border_id

C42

Dfilter

Attempts:

3 left

💡 Hint

Common Mistakes

Using filter() which returns a queryset, not a single object.

Using wrong field name or value.

get() fetches the single Order with order_id=42. The key and value must be correct. The exception handles the case when no order is found.

Practice

1. What does the Django get() method do when used on a model's manager?

easy

A. It updates the object matching the filter.

B. It returns a list of all objects matching the filter.

C. It returns exactly one object matching the filter or raises an error.

D. It deletes the object matching the filter.

Solution

1. Step 1: Understand the purpose of get()

   The get() method is designed to find exactly one object that matches the given filter criteria.

2. Step 2: Recognize behavior on multiple or zero matches

   If no objects or more than one object match, get() raises an error instead of returning multiple objects or none.

3. Final Answer:

   It returns exactly one object matching the filter or raises an error. -> Option C

4. Quick Check:

   get() returns one object or error [OK]

Hint: Remember: get() expects one object, else error [OK]

Common Mistakes:

• Thinking get() returns multiple objects like filter()
• Assuming get() updates or deletes objects
• Expecting get() to return None if no match

2. Which of the following is the correct syntax to get a single Book object with id=5 using Django ORM?

easy

A. Book.objects.get(id=5)

B. Book.get.objects(id=5)

C. Book.objects.filter(id=5)

D. Book.objects.get.filter(id=5)

Solution

1. Step 1: Recall correct method call order

   In Django ORM, get() is called on the model manager accessed by objects.

2. Step 2: Verify syntax correctness

   The correct syntax is Book.objects.get(id=5). Other options misuse method chaining or order.

3. Final Answer:

   Book.objects.get(id=5) -> Option A

4. Quick Check:

   Correct syntax = Book.objects.get(id=5) [OK]

Hint: Use Model.objects.get(field=value) syntax [OK]

Common Mistakes:

• Swapping method and manager order
• Calling get() after filter() incorrectly
• Using get() as an attribute instead of method

3. Given the model Author with two entries having name='Alice', what happens when you run Author.objects.get(name='Alice')?

medium

A. Returns the first Author object with name 'Alice'.

B. Returns a list of Author objects with name 'Alice'.

C. Raises a DoesNotExist exception.

D. Raises a MultipleObjectsReturned exception.

Solution

1. Step 1: Understand get() behavior with multiple matches

   If more than one object matches the filter, get() raises a MultipleObjectsReturned exception.

2. Step 2: Apply to given scenario

   Since two Authors have name='Alice', calling get(name='Alice') triggers this exception.

3. Final Answer:

   Raises a MultipleObjectsReturned exception. -> Option D

4. Quick Check:

   Multiple matches cause MultipleObjectsReturned [OK]

Hint: Multiple matches with get() cause MultipleObjectsReturned error [OK]

Common Mistakes:

• Assuming get() returns first match silently
• Expecting get() to return a list
• Confusing DoesNotExist with multiple matches

4. What is wrong with this code snippet?

user = User.objects.get(username='john')
print(user.email)

Assuming no user with username 'john' exists.

medium

A. It will print an empty string for email.

B. It will raise a DoesNotExist exception.

C. It will raise a MultipleObjectsReturned exception.

D. It will return None and cause AttributeError on print.

Solution

1. Step 1: Check behavior when no object matches get()

   If no object matches the filter, get() raises a DoesNotExist exception.

2. Step 2: Apply to given code

   Since no user with username 'john' exists, User.objects.get(username='john') raises DoesNotExist before print runs.

3. Final Answer:

   It will raise a DoesNotExist exception. -> Option B

4. Quick Check:

   No match with get() causes DoesNotExist [OK]

Hint: No match with get() raises DoesNotExist error [OK]

Common Mistakes:

• Expecting get() to return None if no match
• Assuming print runs without error
• Confusing DoesNotExist with MultipleObjectsReturned

5. You want to get a single Product with sku='12345'. If it doesn't exist, you want to create it with name='New Product'. Which code correctly does this using get()?

hard

A. try:
product = Product.objects.get(sku='12345')
except Product.DoesNotExist:
product = Product.objects.create(sku='12345', name='New Product')

B. product = Product.objects.get_or_create(sku='12345', name='New Product')

C. product = Product.objects.get(sku='12345') or Product.objects.create(sku='12345', name='New Product')

D. product = Product.objects.filter(sku='12345').get_or_create(name='New Product')

Solution

1. Step 1: Understand get() behavior and exception handling

   get() raises DoesNotExist if no object matches, so use try-except to handle this.

2. Step 2: Review options for correct usage

   try: product = Product.objects.get(sku='12345') except Product.DoesNotExist: product = Product.objects.create(sku='12345', name='New Product') uses try-except with get() and creates the object if not found, which is correct. product = Product.objects.get_or_create(sku='12345', name='New Product') uses get_or_create() which is a different method, not get(). The other options misuse method chaining and will cause errors.

3. Final Answer:

   Use try-except with get() and create if not found. -> Option A

4. Quick Check:

   Handle DoesNotExist with try-except for get() [OK]

Hint: Use try-except DoesNotExist to handle get() missing object [OK]

Common Mistakes:

• Using get_or_create() instead of get()
• Assuming get() returns None if no match
• Chaining get_or_create() after filter() incorrectly