Setting and getting session data in Django - Mini Project: Build & Apply

Setting and Getting Session Data in Django

📖 Scenario: You are building a simple Django web app that tracks a user's favorite color during their visit. You want to store this color in the session so it remembers the choice as the user navigates pages.

🎯 Goal: Build a Django view that sets a session variable called favorite_color to a specific value, and another view that reads and displays this session value.

📋 What You'll Learn

Create a Django view function called set_color that sets request.session['favorite_color'] to the string 'blue'.

Create a Django view function called get_color that reads request.session['favorite_color'] and returns it in an HttpResponse.

Use the Django HttpResponse class to return simple text responses.

Ensure the session data is properly set and retrieved using Django's session framework.

💡 Why This Matters

🌍 Real World

Web apps often need to remember user preferences or temporary data during a visit. Sessions let you store this data securely on the server side.

💼 Career

Understanding session management is essential for backend web developers working with Django or similar frameworks to maintain user state and preferences.

1

Create the set_color view to set session data

Write a Django view function called set_color that takes request as a parameter and sets request.session['favorite_color'] to the string 'blue'. Return an HttpResponse with the text 'Color set to blue'.

Django

from django.http import HttpResponse

def set_color(request):
    # Your code here

Hint

Use request.session['favorite_color'] = 'blue' to store the color in the session.

2

Create the get_color view to read session data

Add a Django view function called get_color that takes request as a parameter and reads the session value request.session['favorite_color']. Return an HttpResponse with the text 'Favorite color is: ' followed by the session value.

Django

from django.http import HttpResponse

def set_color(request):
    request.session['favorite_color'] = 'blue'
    return HttpResponse('Color set to blue')

def get_color(request):
    # Your code here

Hint

Use color = request.session['favorite_color'] to get the stored color.

3

Add a check for missing session data in get_color

Modify the get_color view to use request.session.get('favorite_color', 'not set') to safely get the session value or return 'not set' if it does not exist. Return an HttpResponse with the text 'Favorite color is: ' followed by this value.

Django

from django.http import HttpResponse

def set_color(request):
    request.session['favorite_color'] = 'blue'
    return HttpResponse('Color set to blue')

def get_color(request):
    # Your code here

Hint

Use request.session.get('favorite_color', 'not set') to avoid errors if the session key is missing.

4

Add URL patterns for the views

Create a Django urlpatterns list with two path entries: one for set_color at URL 'set/' and one for get_color at URL 'get/'. Import path from django.urls and import the two view functions.

Django

from django.http import HttpResponse
from django.urls import path

# Your code here

Hint

Use path('set/', set_color) and path('get/', get_color) inside urlpatterns.

Practice

1. What is the correct way to store a user's favorite color in Django session inside a view?

easy

A. request.session['favorite_color'] = 'blue'

B. request.session.set('favorite_color', 'blue')

C. session['favorite_color'] = 'blue'

D. request.set_session('favorite_color', 'blue')

Solution

1. Step 1: Understand Django session assignment

   In Django, session data is stored by assigning a value to a key in request.session like a dictionary.

2. Step 2: Identify correct syntax for setting session data

   The correct syntax is request.session['key'] = value. Methods like set or set_session do not exist.

3. Final Answer:

   request.session['favorite_color'] = 'blue' -> Option A

4. Quick Check:

   Set session data with dictionary syntax [OK]

Hint: Use dictionary style assignment to set session data [OK]

Common Mistakes:

• Using non-existent methods like set() or set_session()
• Trying to assign session data without request.session
• Using session variable without request object

2. Which of the following is the correct syntax to retrieve a session value safely with a default in Django?

easy

A. request.session.get('user_id' : None)

B. request.session['user_id', None]

C. request.session.fetch('user_id', None)

D. request.session.get('user_id', None)

Solution

1. Step 1: Recall the method to get session data safely

   Django sessions use the dictionary method get(key, default) to retrieve values safely without error if key is missing.

2. Step 2: Identify correct syntax

   The correct syntax is request.session.get('user_id', None). Using brackets with comma or colon is invalid syntax, and fetch is not a valid method.

3. Final Answer:

   request.session.get('user_id', None) -> Option D

4. Quick Check:

   Use get() with key and default [OK]

Hint: Use get() method with key and default to avoid errors [OK]

Common Mistakes:

• Using brackets with comma or colon inside session access
• Using non-existent fetch() method
• Accessing session key directly without default causing KeyError

3. Given the following Django view code snippet, what will be the output if the session has no 'visits' key initially?

def my_view(request):
    visits = request.session.get('visits', 0)
    visits += 1
    request.session['visits'] = visits
    return HttpResponse(f"Visit count: {visits}")

medium

A. Visit count: None

B. Visit count: 0

C. Visit count: 1

D. KeyError exception

Solution

1. Step 1: Understand default value usage in get()

   The code uses request.session.get('visits', 0) which returns 0 if 'visits' key is missing.

2. Step 2: Follow the increment and assignment

   It adds 1 to visits (0 + 1 = 1), then stores it back in session and returns the string with visits value.

3. Final Answer:

   Visit count: 1 -> Option C

4. Quick Check:

   Default 0 + 1 increment = 1 [OK]

Hint: Default value in get() prevents KeyError, then increment [OK]

Common Mistakes:

• Assuming visits starts at None or causes error
• Forgetting to add 1 before storing
• Expecting KeyError when key is missing

4. Identify the error in this Django view code that tries to get a session value:

def view(request):
    user = request.session['user', 'guest']
    return HttpResponse(user)

medium

A. TypeError because session is not subscriptable

B. KeyError if 'user' key missing

C. Returns 'guest' string correctly

D. SyntaxError due to incorrect session key access

Solution

1. Step 1: Analyze session key access syntax

   The code uses request.session['user', 'guest'] which passes a tuple ('user', 'guest') as the key.

2. Step 2: Identify correct way to provide default

   This raises KeyError if the tuple key is missing. To get 'user' with default 'guest', use request.session.get('user', 'guest').

3. Final Answer:

   KeyError if 'user' key missing -> Option B

4. Quick Check:

   Tuple in brackets causes KeyError [OK]

Hint: Use get() for default, not tuple keys in brackets [OK]

Common Mistakes:

• Using tuple inside brackets for session key
• Expecting bracket syntax to accept default value
• Confusing dictionary get() method with bracket access

5. You want to track a user's last visited page URL in session and display it on the next page visit. Which code snippet correctly sets and gets this session data in Django?

hard

A. last = request.session.get('last_page', 'None'); request.session['last_page'] = request.path

B. request.session['last_page'] = request.path; last = request.session.get('last_page', 'None')

C. request.session.set('last_page', request.path); last = request.session['last_page']

D. last = request.session['last_page']; request.session['last_page'] = request.path

Solution

1. Step 1: Understand the order of getting and setting session data

   To show the last visited page, first get the stored value, then update it with the current page path.

2. Step 2: Identify correct code order and methods

   last = request.session.get('last_page', 'None'); request.session['last_page'] = request.path first retrieves last_page with a default, then updates it with request.path. Other options set before getting or use invalid methods.

3. Final Answer:

   last = request.session.get('last_page', 'None'); request.session['last_page'] = request.path -> Option A

4. Quick Check:

   Get old value before updating session [OK]

Hint: Get session value before updating it to show previous data [OK]

Common Mistakes:

• Setting session before getting old value loses previous data
• Using non-existent set() method
• Accessing session key directly without default causing error