Field lookups (exact, contains, gt, lt) in Django - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to filter users with the exact username 'alice'.

Django

users = User.objects.filter(username__[1]='alice')

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

Agt

Bcontains

Cexact

Dlt

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'contains' will match usernames that include 'alice' anywhere, not exactly.

Using 'gt' or 'lt' are for greater or less than comparisons, not exact matches.

The exact lookup matches the field value exactly. Here, it filters users whose username is exactly 'alice'.

2fill in blank

medium

Complete the code to find products whose name contains the word 'book'.

Django

products = Product.objects.filter(name__[1]='book')

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

Acontains

Bgt

Cexact

Dlt

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'exact' will only find names exactly equal to 'book'.

Using 'gt' or 'lt' are for numeric or date comparisons, not strings.

The contains lookup finds records where the field includes the given substring anywhere inside it.

3fill in blank

hard

Fix the error in filtering orders with amount greater than 100.

Django

orders = Order.objects.filter(amount__[1]=100)

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

Agt

Bexact

Ccontains

Dlt

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'contains' or 'exact' will not compare numeric values properly.

Using 'lt' means 'less than', which is the opposite of what is needed.

The gt lookup means 'greater than'. It filters orders with amount more than 100.

4fill in blank

hard

Fill both blanks to filter events with date less than '2024-01-01' and name containing 'conference'.

Django

events = Event.objects.filter(date__[1]='2024-01-01', name__[2]='conference')

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

Alt

Bexact

Ccontains

Dgt

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'gt' instead of 'lt' for date filtering.

Using 'exact' instead of 'contains' for substring matching.

Use lt for dates less than the given date, and contains to find names including 'conference'.

5fill in blank

hard

Fill all three blanks to create a dictionary with keys as lowercase usernames and values as emails for users with id greater than 10.

Django

user_dict = {user.username.[1](): user.[2] for user in User.objects.filter(id__[3]=10)}

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

Alower

Bemail

Cgt

Dcontains

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'contains' as a lookup for numeric id filtering.

Using 'upper' instead of 'lower' for username keys.

Using 'exact' instead of 'gt' for filtering ids.

Use lower() to convert usernames to lowercase (common for keys), email to get user emails, and gt to filter users with id greater than 10.

Practice

1. Which Django field lookup would you use to find records where a field exactly matches a given value?

easy

A. exact

B. contains

C. gt

D. lt

Solution

1. Step 1: Understand the purpose of each lookup

   The exact lookup matches fields that are exactly equal to the given value. contains checks for substring presence, gt means greater than, and lt means less than.

2. Step 2: Match the requirement to the lookup

   Since the question asks for exact matches, exact is the correct lookup.

3. Final Answer:

   exact -> Option A

4. Quick Check:

   Exact match = exact [OK]

Hint: Exact match uses 'exact' lookup in Django queries [OK]

Common Mistakes:

• Confusing 'contains' with exact match
• Using 'gt' or 'lt' for equality checks
• Assuming 'exact' is default without specifying

2. Which of the following is the correct syntax to filter a Django model Book for titles containing the word 'django'?

easy

A. Book.objects.filter(title__exact='django')

B. Book.objects.filter(title__gt='django')

C. Book.objects.filter(title__contains='django')

D. Book.objects.filter(title__lt='django')

Solution

1. Step 1: Identify the lookup for substring matching

   The contains lookup is used to find records where the field contains the given substring anywhere inside it.

2. Step 2: Check the syntax for filtering

   The correct syntax uses double underscores to specify the lookup: title__contains='django'.

3. Final Answer:

   Book.objects.filter(title__contains='django') -> Option C

4. Quick Check:

   Substring search = contains [OK]

Hint: Use __contains for substring filters in Django queries [OK]

Common Mistakes:

• Using __exact for substring search
• Using __gt or __lt for string matching
• Missing double underscores in lookup

3. Given the model Product with a field price, what will this query return?

Product.objects.filter(price__gt=100)

medium

A. All products with price greater than 100

B. All products with price exactly 100

C. All products with price less than 100

D. All products with price containing '100'

Solution

1. Step 1: Understand the lookup used

   The lookup price__gt=100 means filter products where the price is greater than 100.

2. Step 2: Interpret the query result

   The query returns all products with price values strictly greater than 100, excluding 100 itself.

3. Final Answer:

   All products with price greater than 100 -> Option A

4. Quick Check:

   gt means greater than [OK]

Hint: gt means greater than in Django filters [OK]

Common Mistakes:

• Confusing gt with exact or contains
• Thinking gt includes the value 100
• Assuming it filters less than 100

4. You wrote this Django query but it raises an error:

Entry.objects.filter(date__gt='2023-01-01')

What is the most likely cause?

medium

A. You must use 'exact' lookup for date filtering

B. The field 'date' is not a DateField or DateTimeField

C. The date string format is incorrect for filtering

D. The lookup 'gt' is not valid for date fields

Solution

1. Step 1: Check field type compatibility

   The gt lookup works with fields that support ordering like DateField or DateTimeField. If date is not one of these, the query will error.

2. Step 2: Validate other options

   The lookup gt is valid for date fields, and the string format is acceptable for Django's date parsing. Using exact is not required.

3. Final Answer:

   The field 'date' is not a DateField or DateTimeField -> Option B

4. Quick Check:

   gt requires comparable field type [OK]

Hint: Ensure field type supports lookup before filtering [OK]

Common Mistakes:

• Assuming all fields support gt lookup
• Incorrect date string format causing error
• Using exact lookup unnecessarily

5. You want to find all Order records where the status field contains 'pending' (case insensitive) and the total is less than 500. Which Django query correctly applies these filters?

hard

A. Order.objects.filter(status__contains='pending', total__gt=500)

B. Order.objects.filter(status__contains='pending', total__lt=500)

C. Order.objects.filter(status__exact='pending', total__lt=500)

D. Order.objects.filter(status__icontains='pending', total__lt=500)

Solution

1. Step 1: Choose case-insensitive substring lookup

   To find 'pending' regardless of case, use icontains instead of contains.

2. Step 2: Apply less than filter on total

   The total__lt=500 filters orders with total less than 500.

3. Step 3: Combine filters correctly

   Both filters are passed as keyword arguments to filter() to apply AND logic.

4. Final Answer:

   Order.objects.filter(status__icontains='pending', total__lt=500) -> Option D

5. Quick Check:

   Case-insensitive contains + less than = icontains + lt [OK]

Hint: Use icontains for case-insensitive substring filters [OK]

Common Mistakes:

• Using contains instead of icontains for case insensitivity
• Mixing lt and gt incorrectly
• Using exact instead of contains for substring search