Form validation (is_valid, cleaned_data) in Django - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the is_valid() method do in a Django form?

The is_valid() method checks if the form data meets all validation rules. It returns True if the data is valid, otherwise False. It also prepares cleaned data for use.

beginner

What is cleaned_data in Django forms?

cleaned_data is a dictionary that holds the validated and converted form data after is_valid() is called. It contains safe data you can use in your code.

beginner

When should you access cleaned_data in a Django form?

You should access cleaned_data only after is_valid() returns True. Accessing it before validation may cause errors.

intermediate

How can you add custom validation logic in a Django form?

You can add a method named clean_fieldname() for a specific field or override the clean() method for the whole form to add custom validation.

beginner

What happens if is_valid() returns False?

If is_valid() returns False, the form has errors. You can check form.errors to see what went wrong and show messages to the user.

What does form.is_valid() return if the form data is correct?

A True

B False

C None

D An error message

is_valid() returns True when all form data passes validation.

Where do you find the cleaned and safe form data after validation?

A form.errors

B form.cleaned_data

C form.raw_data

D form.data

cleaned_data holds the validated and converted form data.

When should you NOT access form.cleaned_data?

A Inside <code>clean()</code> method

B After <code>is_valid()</code> returns True

C Before calling <code>is_valid()</code>

D When form is submitted

Accessing cleaned_data before validation can cause errors.

How do you add validation for a single field in a Django form?

A Call <code>is_valid()</code> twice

B Override <code>save()</code> method

C Use <code>form.errors</code>

D Define a method <code>clean_fieldname()</code>

Custom validation for a field uses clean_fieldname().

What attribute contains error messages if validation fails?

A form.errors

B form.cleaned_data

C form.is_valid

D form.data

form.errors holds error messages after failed validation.

Explain how is_valid() and cleaned_data work together in Django form validation.

Think about the order of validation and data access.

Describe how to add custom validation to a specific field in a Django form.

Focus on naming and purpose of the method.