Method filter

python/pathway/internals/table.py:497–533

Filter a table according to `filter_expression` condition. Args: filter_expression: `ColumnExpression` that specifies the filtering condition. Returns: Table: Result has the same schema as `self` and its ids are subset of `self.id`. Example:

(self, filter_expression: expr.ColumnExpression)

    @desugar
    @check_arg_types
    def filter(self, filter_expression: expr.ColumnExpression) -> Table[TSchema]:
        """Filter a table according to `filter_expression` condition.


        Args:
            filter_expression: `ColumnExpression` that specifies the filtering condition.

        Returns:
            Table: Result has the same schema as `self` and its ids are subset of `self.id`.


        Example:

        >>> import pathway as pw
        >>> vertices = pw.debug.table_from_markdown('''
        ... label outdegree
        ...     1         3
        ...     7         0
        ... ''')
        >>> filtered = vertices.filter(vertices.outdegree == 0)
        >>> pw.debug.compute_and_print(filtered, include_id=False)
        label | outdegree
        7     | 0
        """
        filter_type = self.eval_type(filter_expression)
        if filter_type != dt.BOOL:
            raise TypeError(
                f"Filter argument of Table.filter() has to be bool, found {filter_type}."
            )
        ret = self._filter(filter_expression)
        if (
            filter_col := expr.get_column_filtered_by_is_none(filter_expression)
        ) is not None and filter_col.table == self:
            name = filter_col.name
            dtype = self._columns[name].dtype
            ret = ret.update_types(**{name: dt.unoptionalize(dtype)})
        return ret

    @trace_user_frame
    @desugar