How to raise multiple ValidationError on Django?

I do not recommend validating every single field inside only one function. What you should do instead is use one function to validate one field, it is way easier and simpler. If you want to do multiple validations you can find the documentation for handling multiple errors at link. The documentation shows the example below:

# Good
raise ValidationError([
    ValidationError(_('Error 1'), code='error1'),
    ValidationError(_('Error 2'), code='error2'),
])

# Bad
raise ValidationError([
    _('Error 1'),
    _('Error 2'),
])

And here is an example of mine:

def validate_field(value):
    errors = []

    if len(value) > 50:
        errors.append(ValidationError(
            'Error message'
        ))
    if not value.isalpha():
        errors.append(ValidationError(
            'Error message'
        ))

    if errors:
        raise ValidationError(errors)

You throw one ValidationError with multiple fields errors inside:

    raise ValidationError({
        'field_name_1': ["Field not allowed to change"],
        'field_name_2': ["Field not allowed to change"],
    })

Django 3.0+ style should follow docs:

raise ValidationError([
    ValidationError('Error 1', code='error1'),
    ValidationError('Error 2', code='error2'),
])