def _extract_colnums(self, columns=None):
if columns is None:<EOL><INDENT>return numpy.arange(self._ncol, dtype='<STR_LIT>')<EOL><DEDENT>if not isinstance(columns, (tuple, list, numpy.ndarray)):<EOL><INDENT>return self._extract_colnum(columns)<EOL><DEDENT>colnums = numpy.zeros(len(columns), dtype='<STR_LIT>')<EOL>for i in xrange(colnums.size):<EOL><INDENT>colnums[i] = self._extract_colnum(columns[i])<EOL><DEDENT>colnums = numpy.unique(colnums)<EOL>return colnums<EOL>
Extract an array of columns from the input