Class TableSlice

python/pathway/internals/table_slice.py:16–153

Collection of references to Table columns. Created by Table.slice method, or automatically by using left/right/this constructs. Supports basic column manipulation methods. Example: >>> import pathway as pw >>> t1 = pw.debug.table_from_markdown(''' ... age | owner | pet

class TableSlice:
    """Collection of references to Table columns.
    Created by Table.slice method, or automatically by using left/right/this constructs.
    Supports basic column manipulation methods.

    Example:

    >>> import pathway as pw
    >>> t1 = pw.debug.table_from_markdown('''
    ... age | owner | pet
    ... 10  | Alice | dog
    ... 9   | Bob   | dog
    ... 8   | Alice | cat
    ... 7   | Bob   | dog
    ... ''')
    >>> t1.slice.without("age").with_suffix("_col")
    TableSlice({'owner_col': <table1>.owner, 'pet_col': <table1>.pet})
    """

    _mapping: dict[str, ColumnReference]
    _table: Table

    def __init__(self, mapping, table):
        self._mapping = mapping
        self._table = table

    def __iter__(self):
        return iter(self._mapping.values())

    def __repr__(self):
        return f"TableSlice({self._mapping})"

    def keys(self):
        return self._mapping.keys()

    @overload
    def __getitem__(self, args: str | ColumnReference) -> ColumnReference: ...

    @overload
    def __getitem__(self, args: list[str | ColumnReference]) -> TableSlice: ...

    @trace_user_frame
    def __getitem__(
        self, arg: str | ColumnReference | list[str | ColumnReference]
    ) -> ColumnReference | TableSlice:
        if isinstance(arg, (ColumnReference, str)):
            return self._mapping[self._normalize(arg)]
        else:
            return TableSlice({self._normalize(k): self[k] for k in arg}, self._table)

    @trace_user_frame
    def __getattr__(self, name: str) -> ColumnReference:
        from pathway.internals import Table

        if hasattr(Table, name) and name != "id":
            raise ValueError(
                f"{name!r} is a method name. It is discouraged to use it as a column"
                + f" name. If you really want to use it, use [{name!r}]."