django.forms.form.py

def errors(self):
   """Return an ErrorDict for the data provided for the form."""
   if self._errors is None:
      self.full_clean()
   return self._errors


def is_valid(self):
   """Return True if the form has no errors, or False otherwise."""
   return self.is_bound and not self.errors

def full_clean(self):
   """
   Clean all of self.data and populate self._errors and self.cleaned_data.
   """
   self._errors = ErrorDict()
   if not self.is_bound:  # Stop further processing.
      return
   self.cleaned_data = {}
   # If the form is permitted to be empty, and none of the form data has
   # changed from the initial data, short circuit any validation.
   if self.empty_permitted and not self.has_changed():
      return

   self._clean_fields()
   self._clean_form()
   self._post_clean()