code: def value_from_datadict(self, data, files, name):
          '''Generate a single value from multi-part form data.  Constructs a W3C
          date based on values that are set, leaving out day and month if they are
          not present.
  
          :param data: dictionary of data submitted by the form
          :param files: - unused
          :param name: base name of the form field
          :returns: string value
          '''
  
          y = data.get(self.year_field % name)
          m = data.get(self.month_field % name)
          d = data.get(self.day_field % name)
  
          if y == 'YYYY':
              y = ''
  
          if m == 'MM':
              m = ''
  
          if d == 'DD':
              d = ''
  
          date = y
          if m:
              date += '-%s' % m
              if d:
                  date += '-%s' % d
          return datf value_from_datadict(self, data, files, name):
          '''Generate a single value from multi-part form data.  Constructs a W3C
          date based on values that are set, leaving out day and month if they are
          not present.
  
          :param data: dictionary of data submitted by the form
          :param files: - unused
          :param name: base name of the form field
          :returns: string value
          '''
  
          y = data.get(self.year_field % name)
          m = data.get(self.month_field % name)
          d = data.get(self.day_field % name)
  
          if y == 'YYYY':
              y = ''
  
          if m == 'MM':
              m = ''
  
          if d == 'DD':
              d = ''
  
          date = y
          if m:
              date += '-%s' % m
              if d:
                  date += '-%s' % d
          return date
docs: Generate a single value from multi-part form data.  Constructs a W3C
          date based on values that are set, leaving out day and month if they are
          not present.
  
          :param data: dictionary of data submitted by the form
          :param files: - unused
          :param name: base name of the form field
          :returns: string value