Field lookups (exact, contains, gt, lt) in Django - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What does this Django query return?

Consider a Django model Book with a field title. What does this query return?

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

A All books with titles that include the exact word 'django' only

B All books with titles that contain the substring 'django' anywhere, case-insensitive

C All books with titles that contain the substring 'django' anywhere, case-sensitive

D All books with titles exactly equal to 'django'

💡 Hint

Think about whether the lookup is case-sensitive or not.

The '__contains' lookup in Django filters for records where the field contains the given substring exactly as typed, so it is case-sensitive.

📝 Syntax

intermediate

Which query correctly filters for books published after 2010?

Given a Django model Book with a field published_year (integer), which query correctly filters books published after 2010?

A Book.objects.filter(published_year__after=2010)

B Book.objects.filter(published_year>2010)

C Book.objects.filter(published_year__gte=2010)

D Book.objects.filter(published_year__gt=2010)

💡 Hint

Look for the correct Django field lookup suffix for 'greater than'.

The correct lookup for 'greater than' in Django ORM is '__gt'. The option with '__gte' means 'greater than or equal to', which is not the same.

🔧 Debug

advanced

Why does this query raise an error?

Given a Django model Author with a field name, why does this query raise an error?

Author.objects.filter(name__contains)

A Because the '__contains' lookup requires a value to compare against, but none was provided

B Because '__contains' is not a valid Django lookup

C Because 'name' field does not support lookups

D Because the query should use '__icontains' instead

💡 Hint

Check the syntax of the filter method and its arguments.

The '__contains' lookup requires a value to compare the field against. Omitting the value causes a TypeError.

❓ state_output

advanced

What is the count of books returned?

Assume the database has these Book titles:
- 'Django for Beginners'
- 'Learning Python'
- 'Advanced Django'
- 'Python Cookbook'

What is the count of books returned by:
Book.objects.filter(title__exact='Django for Beginners').count()

A 2

B 1

C 0

D 4

💡 Hint

The '__exact' lookup matches the whole field exactly.

Only one book title exactly matches 'Django for Beginners'.

🧠 Conceptual

expert

Which lookup is case-insensitive for substring matching?

You want to filter a Django model's text field to find records containing a substring regardless of case. Which lookup should you use?

A __icontains

B __exact

C __contains

D __iexact

💡 Hint

Look for the lookup with 'i' prefix for case-insensitive.

The '__icontains' lookup performs a case-insensitive substring match.

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