Method align

pandas/core/generic.py:9693–9858

Align two objects on their axes with the specified join method. Join method is specified for each axis Index. Parameters ---------- other : DataFrame or Series The object to align with. join : {'outer', 'inner', 'left', 'right'}, default

(
        self,
        other: NDFrameT,
        join: AlignJoin = "outer",
        axis: Axis | None = None,
        level: Level | None = None,
        copy: bool | lib.NoDefault = lib.no_default,
        fill_value: Hashable | None = None,
    )

    @final
    def align(
        self,
        other: NDFrameT,
        join: AlignJoin = "outer",
        axis: Axis | None = None,
        level: Level | None = None,
        copy: bool | lib.NoDefault = lib.no_default,
        fill_value: Hashable | None = None,
    ) -> tuple[Self, NDFrameT]:
        """
        Align two objects on their axes with the specified join method.

        Join method is specified for each axis Index.

        Parameters
        ----------
        other : DataFrame or Series
            The object to align with.
        join : {'outer', 'inner', 'left', 'right'}, default 'outer'
            Type of alignment to be performed.

            * left: use only keys from left frame, preserve key order.
            * right: use only keys from right frame, preserve key order.
            * outer: use union of keys from both frames, sort keys lexicographically.
            * inner: use intersection of keys from both frames,
              preserve the order of the left keys.

        axis : allowed axis of the other object, default None
            Align on index (0), columns (1), or both (None).
        level : int or level name, default None
            Broadcast across a level, matching Index values on the
            passed MultiIndex level.
        copy : bool, default False
            This keyword is now ignored; changing its value will have no
            impact on the method.

            .. deprecated:: 3.0.0

                This keyword is ignored and will be removed in pandas 4.0. Since
                pandas 3.0, this method always returns a new object using a lazy
                copy mechanism that defers copies until necessary
                (Copy-on-Write). See the `user guide on Copy-on-Write
                <https://pandas.pydata.org/docs/dev/user_guide/copy_on_write.html>`__
                for more details.

        fill_value : scalar, default np.nan
            Value to use for missing values. Defaults to NaN, but can be any
            "compatible" value.

        Returns
        -------
        tuple of (Series/DataFrame, type of other)
            Aligned objects.

        See Also
        --------
        Series.align : Align two objects on their axes with specified join method.
        DataFrame.align : Align two objects on their axes with specified join method.