Setting and getting session data in Django - Step-by-Step Execution

Concept Flow - Setting and getting session data

Request received

↓

Access session object

↓

Set session key-value

↓

Get session value by key

↓

Use value in response

↓

Send response back

This flow shows how a Django view sets a value in the session and then retrieves it to use in the response.

Execution Sample

Django

from django.http import HttpResponse

def view(request):
    request.session['color'] = 'blue'
    favorite = request.session.get('color', 'red')
    return HttpResponse(f"Favorite color is {favorite}")

This Django view sets a session key 'color' to 'blue' and then gets it to display in the response.

Execution Table

Step	Action	Session State	Value Retrieved	Response Content
1	Request received, session empty	{}	N/A	N/A
2	Set 'color' = 'blue' in session	{'color': 'blue'}	N/A	N/A
3	Get 'color' from session	{'color': 'blue'}	'blue'	N/A
4	Create response with favorite color	{'color': 'blue'}	'blue'	"Favorite color is blue"
5	Send response back	{'color': 'blue'}	'blue'	"Favorite color is blue"

💡 Response sent with session data set and retrieved successfully.

Variable Tracker

Variable	Start	After Step 2	After Step 3	Final
request.session	{}	{'color': 'blue'}	{'color': 'blue'}	{'color': 'blue'}
favorite	N/A	N/A	'blue'	'blue'

Key Moments - 2 Insights

Why do we use request.session.get('color', 'red') instead of request.session['color']?

Using get() avoids errors if 'color' is not set in the session. It returns 'red' as a default instead of crashing. See step 3 in execution_table where get() safely retrieves the value.

Does setting request.session['color'] = 'blue' immediately save data to the browser?

No, Django saves session data when the response is sent. The session dictionary updates in memory first (step 2), then persists after response (step 5).

Visual Quiz - 3 Questions

Look at the execution table, what is the session state after step 2?

A {"color": "blue"}

B {}

C {"color": "red"}

D N/A

💡 Hint

Check the 'Session State' column at step 2 in the execution_table.

At which step is the session value 'color' retrieved?

A Step 1

B Step 3

C Step 2

D Step 4

💡 Hint

Look for 'Get 'color' from session' action in the execution_table.

If we change the default in get() to 'green', what will be the response content at step 4 if 'color' was not set?

A "Favorite color is blue"

B "Favorite color is red"

C "Favorite color is green"

D "Favorite color is null"

💡 Hint

Refer to the 'Value Retrieved' and 'Response Content' columns and imagine 'color' missing in session.

Concept Snapshot

Django sessions store data per user.
Set data: request.session['key'] = value
Get data safely: request.session.get('key', default)
Data persists across requests.
Session saves when response is sent.

Full Transcript

This example shows how Django handles session data in a view. When a request comes in, the session starts empty. The code sets a key 'color' to 'blue' in the session dictionary. Then it retrieves this value safely using get(), which returns 'blue'. Finally, the response includes the favorite color. The session data is saved after the response is sent, so it is available in future requests. Using get() prevents errors if the key is missing by providing a default value.

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