Low-level cache API in Django - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ component_behavior

intermediate

What is the output of this Django cache code?

Consider this Django code snippet using the low-level cache API:

from django.core.cache import cache

cache.set('key1', 'value1', timeout=5)
value = cache.get('key1')
print(value)

What will be printed immediately after running this code?

Django

from django.core.cache import cache

cache.set('key1', 'value1', timeout=5)
value = cache.get('key1')
print(value)

A value1

B None

C KeyError

D TimeoutError

💡 Hint

Think about what cache.set and cache.get do immediately after setting a value.

The cache.set stores 'value1' under 'key1' with a 5-second timeout. Immediately after, cache.get('key1') returns 'value1' because the key exists and has not expired.

❓ state_output

intermediate

What is the value of 'result' after this cache operation?

Given this code snippet:

from django.core.cache import cache

cache.set('counter', 10)
result = cache.incr('counter', 5)

What is the value of result after running this?

Django

from django.core.cache import cache

cache.set('counter', 10)
result = cache.incr('counter', 5)

A None

B 15

C 10

D ValueError

💡 Hint

What does cache.incr do to the stored value?

cache.incr increments the integer value stored under 'counter' by 5, so 10 + 5 = 15.

📝 Syntax

advanced

Which option causes a syntax error in Django cache usage?

Identify which code snippet will cause a syntax error when using Django's low-level cache API:

A cache.set('key', 'value', timeout=60)

B cache.get('key', default=None)

C cache.set('key', 'value' timeout=60)

D cache.delete('key')

💡 Hint

Look carefully at the commas separating arguments.

Option C is missing a comma between 'value' and timeout=60, causing a syntax error.

🔧 Debug

advanced

Why does this cache increment raise an error?

Given this code:

from django.core.cache import cache

cache.set('visits', 'ten')
cache.incr('visits')

What error will be raised and why?

Django

from django.core.cache import cache

cache.set('visits', 'ten')
cache.incr('visits')

A ValueError because 'ten' is not an integer

B KeyError because 'visits' does not exist

C TypeError because incr expects a string

D No error, increments to 'ten1'

💡 Hint

cache.incr expects the stored value to be an integer.

cache.incr tries to add 1 to the stored value. Since 'ten' is a string, it raises ValueError.

🧠 Conceptual

expert

Which statement about Django's low-level cache API is TRUE?

Select the correct statement about Django's low-level cache API behavior:

A cache.delete() raises an error if the key does not exist

B cache.set() automatically serializes complex Python objects without configuration

C cache.incr() can increment keys that do not exist by creating them with value 1

D cache.get() returns None if the key does not exist and no default is provided

💡 Hint

Think about default return values and error handling in cache methods.

cache.get() returns None if the key is missing and no default is given. cache.set() requires objects to be serializable. cache.incr() raises a ValueError if the key does not exist. cache.delete() does not raise an error if the key is missing.