Django Tutorial #17: Django Form Submission Flow & Built-in Validators Explained by
In Session 17 of the BasicToTop Django Tutorial Series, we go deeper into what happens in the backend when a user clicks the Submit button and how Django form validation works using built-in validators.
This session focuses on understanding:
How request data reaches the view function
How Django processes GET and POST requests
How form.is_valid() works internally
How to use Django’s built-in validators
How to write custom validators
🔁 What Happens After Clicking the Submit Button?
When the user clicks the Submit button:
1️⃣ Browser sends an HTTP POST request
2️⃣ Request reaches the mapped URL
3️⃣ Django calls the corresponding view function
4️⃣ Form data is available inside request.POST
5️⃣ Form instance is created using POST data
6️⃣ form.is_valid() triggers validation
7️⃣ Validators are executed field by field
8️⃣ Errors are returned if validation fails
9️⃣ Cleaned data is available if validation passes
🧠 Topics Covered in This Session
✅ How form submission works internally
✅ Request → URL → View → Form flow
✅ Difference between GET and POST in backend
✅ What happens inside form.is_valid()
✅ Built-in validators in Django
✅ Custom validator function
✅ Field-level validation using validators
✅ Combining validators with clean() method
📌 Line-by-line meaning:
request.method == 'POST' → checks form submission
ContactUsForm(request.POST) → binds user input
form.is_valid() → runs all validators
cleaned_data → safe, validated data
✅ Built-in Validators in Django
Django provides ready-made validators to enforce rules easily.
Examples:
MinLengthValidator
MaxLengthValidator
📘 What You Learned in Session 17
✔ How form submission reaches backend
✔ How Django processes POST requests
✔ How validators work internally
✔ How to write and use custom validators
✔ How Django stops invalid data automatically
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