List of empty row indices

def count_empty(self, field):
        """
        List of empty row indices
        """
        try:
            df2 = self.df[[field]]
            vals = where(df2.applymap(lambda x: x == ''))
            num = len(vals[0])
        except Exception as e:
            self.err(e, "Can not count empty values")
            return
        self.ok("Found", num, "empty rows in column " + field)