Conditionally Require Only One Field In Django Model Form

Question

Anyway to make a field conditionally required based on whether or not another field in the same form has been filled out?

If field1 has no data, but field2 does
    form is valid.

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If field1 has no data and field2 has no data
    form is invalid

Not looking for any javascript solutions. I feel as it should be solved with django forms, but not quite sure how best to go about it.

Answer 1

Override .clean(self) method, check for self.cleaned_data and raise ValidationError

http://docs.djangoproject.com/en/1.1/ref/forms/validation/#form-field-default-cleaning