Method __init__

pandas/core/frame.py:702–903

(
        self,
        data=None,
        index: Axes | None = None,
        columns: Axes | None = None,
        dtype: Dtype | None = None,
        copy: bool | None = None,
    )

    # Constructors

    def __init__(
        self,
        data=None,
        index: Axes | None = None,
        columns: Axes | None = None,
        dtype: Dtype | None = None,
        copy: bool | None = None,
    ) -> None:
        allow_mgr = False
        if dtype is not None:
            dtype = self._validate_dtype(dtype)

        if isinstance(data, DataFrame):
            data = data._mgr
            allow_mgr = True
            if not copy:
                # if not copying data, ensure to still return a shallow copy
                # to avoid the result sharing the same Manager
                data = data.copy(deep=False)

        if isinstance(data, BlockManager):
            if not allow_mgr:
                # GH#52419
                warnings.warn(
                    f"Passing a {type(data).__name__} to {type(self).__name__} "
                    "is deprecated and will raise in a future version. "
                    "Use public APIs instead.",
                    Pandas4Warning,
                    stacklevel=2,
                )

            data = data.copy(deep=False)
            # first check if a Manager is passed without any other arguments
            # -> use fastpath (without checking Manager type)
            if index is None and columns is None and dtype is None and not copy:
                # GH#33357 fastpath
                NDFrame.__init__(self, data)
                return

        # GH47215
        if isinstance(index, set):
            raise ValueError("index cannot be a set")
        if isinstance(columns, set):
            raise ValueError("columns cannot be a set")

        if copy is None:
            if isinstance(data, dict):
                # retain pre-GH#38939 default behavior
                copy = True
            elif not isinstance(data, (Index, DataFrame, Series)):
                copy = True
            else:
                copy = False

        if data is None:
            index = index if index is not None else default_index(0)
            columns = columns if columns is not None else default_index(0)
            dtype = dtype if dtype is not None else pandas_dtype(object)