Class BlockManager

pandas/core/internals/managers.py:1098–2012

BaseBlockManager that holds 2D blocks.

class BlockManager(libinternals.BlockManager, BaseBlockManager):
    """
    BaseBlockManager that holds 2D blocks.
    """

    ndim = 2

    # ----------------------------------------------------------------
    # Constructors

    def __init__(
        self,
        blocks: Sequence[Block],
        axes: Sequence[Index],
        verify_integrity: bool = True,
    ) -> None:
        if verify_integrity:
            # Assertion disabled for performance
            # assert all(isinstance(x, Index) for x in axes)

            for block in blocks:
                if self.ndim != block.ndim:
                    raise AssertionError(
                        f"Number of Block dimensions ({block.ndim}) must equal "
                        f"number of axes ({self.ndim})"
                    )
                # As of 2.0, the caller is responsible for ensuring that
                #  DatetimeTZBlock with block.ndim == 2 has block.values.ndim ==2;
                #  previously there was a special check for fastparquet compat.

            self._verify_integrity()

    def _verify_integrity(self) -> None:
        mgr_shape = self.shape
        tot_items = sum(len(x.mgr_locs) for x in self.blocks)
        for block in self.blocks:
            if block.shape[1:] != mgr_shape[1:]:
                raise_construction_error(tot_items, block.shape[1:], self.axes)
        if len(self.items) != tot_items:
            raise AssertionError(
                "Number of manager items must equal union of "
                f"block items\n# manager items: {len(self.items)}, # "
                f"tot_items: {tot_items}"
            )

    @classmethod
    def from_blocks(cls, blocks: list[Block], axes: list[Index]) -> Self:
        """
        Constructor for BlockManager and SingleBlockManager with same signature.
        """
        return cls(blocks, axes, verify_integrity=False)

    # ----------------------------------------------------------------
    # Indexing

    def fast_xs(self, loc: int) -> SingleBlockManager:
        """
        Return the array corresponding to `frame.iloc[loc]`.