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# Source code for astropy.io.fits.convenience

    # Licensed under a 3-clause BSD style license - see PYFITS.rst

    """Convenience functions for working with FITS files.

    Convenience functions
    =====================

    The functions in this module provide shortcuts for some of the most basic
    operations on FITS files, such as reading and updating the header.  They are
    included directly in the 'astropy.io.fits' namespace so that they can be used
    like::

        astropy.io.fits.getheader(...)

    These functions are primarily for convenience when working with FITS files in
    the command-line interpreter.  If performing several operations on the same
    file, such as in a script, it is better to *not* use these functions, as each
    one must open and re-parse the file.  In such cases it is better to use
    :func:`astropy.io.fits.open` and work directly with the
    :class:`astropy.io.fits.HDUList` object and underlying HDU objects.

    Several of the convenience functions, such as `getheader` and `getdata` support
    special arguments for selecting which HDU to use when working with a
    multi-extension FITS file.  There are a few supported argument formats for
    selecting the HDU.  See the documentation for `getdata` for an
    explanation of all the different formats.

    .. warning::
        All arguments to convenience functions other than the filename that are
        *not* for selecting the HDU should be passed in as keyword
        arguments.  This is to avoid ambiguity and conflicts with the
        HDU arguments.  For example, to set NAXIS=1 on the Primary HDU:

        Wrong::

            astropy.io.fits.setval('myimage.fits', 'NAXIS', 1)

        The above example will try to set the NAXIS value on the first extension
        HDU to blank.  That is, the argument '1' is assumed to specify an
        HDU.

        Right::

            astropy.io.fits.setval('myimage.fits', 'NAXIS', value=1)

        This will set the NAXIS keyword to 1 on the primary HDU (the default).  To
        specify the first extension HDU use::

            astropy.io.fits.setval('myimage.fits', 'NAXIS', value=1, ext=1)

        This complexity arises out of the attempt to simultaneously support
        multiple argument formats that were used in past versions of PyFITS.
        Unfortunately, it is not possible to support all formats without
        introducing some ambiguity.  A future Astropy release may standardize
        around a single format and officially deprecate the other formats.
    """

    import operator
    import os
    import warnings

    import numpy as np

    from astropy.utils.exceptions import AstropyUserWarning

    from .diff import FITSDiff, HDUDiff
    from .file import FILE_MODES, _File
    from .hdu.base import _BaseHDU, _ValidHDU
    from .hdu.hdulist import HDUList, fitsopen
    from .hdu.image import ImageHDU, PrimaryHDU
    from .hdu.table import BinTableHDU
    from .header import Header
    from .util import (
        _is_dask_array,
        _is_int,
        fileobj_closed,
        fileobj_mode,
        fileobj_name,
        path_like,
    )

    __all__ = [
        "append",
        "delval",
        "getdata",
        "getheader",
        "getval",
        "info",
        "printdiff",
        "setval",
        "table_to_hdu",
        "tabledump",
        "tableload",
        "update",
        "writeto",
    ]

    def getheader(filename, *args, **kwargs):
        """
        Get the header from an HDU of a FITS file.

        Parameters
        ----------
        filename : path-like or file-like
            File to get header from.  If an opened file object, its mode
            must be one of the following rb, rb+, or ab+).

        ext, extname, extver
            The rest of the arguments are for HDU specification.  See the
            `getdata` documentation for explanations/examples.
        **kwargs
            Any additional keyword arguments to be passed to
            `astropy.io.fits.open`.

        Returns
        -------
        header : `Header` object
        """
        mode, closed = _get_file_mode(filename)
        hdulist, extidx = _getext(filename, mode, *args, **kwargs)
        try:
            hdu = hdulist[extidx]
            header = hdu.header
        finally:
            hdulist.close(closed=closed)

        return header

    def getdata(filename, *args, header=None, lower=None, upper=None, view=None, **kwargs):
        """
        Get the data from an HDU of a FITS file (and optionally the
        header).

        Parameters
        ----------
        filename : path-like or file-like
            File to get data from.  If opened, mode must be one of the
            following rb, rb+, or ab+.

        ext
            The rest of the arguments are for HDU specification.
            They are flexible and are best illustrated by examples.

            No extra arguments implies the primary HDU::

                getdata('in.fits')

            .. note::
                Exclusive to ``getdata``: if ``ext`` is not specified
                and primary header contains no data, ``getdata`` attempts
                to retrieve data from first extension HDU.

            By HDU number::

                getdata('in.fits', 0)      # the primary HDU
                getdata('in.fits', 2)      # the second extension HDU
                getdata('in.fits', ext=2)  # the second extension HDU

            By name, i.e., ``EXTNAME`` value (if unique)::

                getdata('in.fits', 'sci')
                getdata('in.fits', extname='sci')  # equivalent

            Note ``EXTNAME`` values are not case sensitive

            By combination of ``EXTNAME`` and EXTVER`` as separate
            arguments or as a tuple::

                getdata('in.fits', 'sci', 2)  # EXTNAME='SCI' & EXTVER=2
                getdata('in.fits', extname='sci', extver=2)  # equivalent
                getdata('in.fits', ('sci', 2))  # equivalent

            Ambiguous or conflicting specifications will raise an exception::

                getdata('in.fits', ext=('sci',1), extname='err', extver=2)

        header : bool, optional
            If `True`, return the data and the header of the specified HDU as a
            tuple.

        lower, upper : bool, optional
            If ``lower`` or ``upper`` are `True`, the field names in the
            returned data object will be converted to lower or upper case,
            respectively.

        view : ndarray, optional
            When given, the data will be returned wrapped in the given ndarray
            subclass by calling::

               data.view(view)

        **kwargs
            Any additional keyword arguments to be passed to
            `astropy.io.fits.open`.

        Returns
        -------
        array : ndarray or `~numpy.recarray` or `~astropy.io.fits.Group`
            Type depends on the type of the extension being referenced.

            If the optional keyword ``header`` is set to `True`, this
            function will return a (``data``, ``header``) tuple.

        Raises
        ------
        IndexError
            If no data is found in searched HDUs.
        """
        mode, closed = _get_file_mode(filename)

        ext = kwargs.get("ext")
        extname = kwargs.get("extname")
        extver = kwargs.get("extver")
        ext_given = not (
            len(args) == 0 and ext is None and extname is None and extver is None
        )

        hdulist, extidx = _getext(filename, mode, *args, **kwargs)
        try:
            hdu = hdulist[extidx]
            data = hdu.data
            if data is None:
                if ext_given:
                    raise IndexError(f"No data in HDU #{extidx}.")

                # fallback to the first extension HDU
                if len(hdulist) == 1:
                    raise IndexError("No data in Primary HDU and no extension HDU found.")
                hdu = hdulist[1]
                data = hdu.data
                if data is None:
                    raise IndexError("No data in either Primary or first extension HDUs.")

            if header:
                hdr = hdu.header
        finally:
            hdulist.close(closed=closed)

        # Change case of names if requested
        trans = None
        if lower:
            trans = operator.methodcaller("lower")
        elif upper:
            trans = operator.methodcaller("upper")
        if trans:
            if data.dtype.names is None:
                # this data does not have fields
                return
            if data.dtype.descr[0][0] == "":
                # this data does not have fields
                return

            for n in data.dtype.names:
                data.columns.change_name(n, trans(n))

        # allow different views into the underlying ndarray.  Keep the original
        # view just in case there is a problem
        if isinstance(view, type) and issubclass(view, np.ndarray):
            data = data.view(view)

        if header:
            return data, hdr
        else:
            return data

    def getval(filename, keyword, *args, **kwargs):
        """
        Get a keyword's value from a header in a FITS file.

        Parameters
        ----------
        filename : path-like or file-like
            Name of the FITS file, or file object (if opened, mode must be
            one of the following rb, rb+, or ab+).

        keyword : str
            Keyword name

        ext, extname, extver
            The rest of the arguments are for HDU specification.
            See `getdata` for explanations/examples.
        **kwargs
            Any additional keyword arguments to be passed to
            `astropy.io.fits.open`.
            *Note:* This function automatically specifies ``do_not_scale_image_data
            = True`` when opening the file so that values can be retrieved from the
            unmodified header.

        Returns
        -------
        keyword value : str, int, or float
        """
        if "do_not_scale_image_data" not in kwargs:
            kwargs["do_not_scale_image_data"] = True

        hdr = getheader(filename, *args, **kwargs)
        return hdr[keyword]

    def setval(
        filename,
        keyword,
        *args,
        value=None,
        comment=None,
        before=None,
        after=None,
        savecomment=False,
        **kwargs,
    ):
        """
        Set a keyword's value from a header in a FITS file.

        If the keyword already exists, it's value/comment will be updated.
        If it does not exist, a new card will be created and it will be
        placed before or after the specified location.  If no ``before`` or
        ``after`` is specified, it will be appended at the end.

        When updating more than one keyword in a file, this convenience
        function is a much less efficient approach compared with opening
        the file for update, modifying the header, and closing the file.

        Parameters
        ----------
        filename : path-like or file-like
            Name of the FITS file, or file object If opened, mode must be update
            (rb+).  An opened file object or `~gzip.GzipFile` object will be closed
            upon return.

        keyword : str
            Keyword name

        value : str, int, float, optional
            Keyword value (default: `None`, meaning don't modify)

        comment : str, optional
            Keyword comment, (default: `None`, meaning don't modify)

        before : str, int, optional
            Name of the keyword, or index of the card before which the new card
            will be placed.  The argument ``before`` takes precedence over
            ``after`` if both are specified (default: `None`).

        after : str, int, optional
            Name of the keyword, or index of the card after which the new card will
            be placed. (default: `None`).

        savecomment : bool, optional
            When `True`, preserve the current comment for an existing keyword.  The
            argument ``savecomment`` takes precedence over ``comment`` if both
            specified.  If ``comment`` is not specified then the current comment
            will automatically be preserved  (default: `False`).

        ext, extname, extver
            The rest of the arguments are for HDU specification.
            See `getdata` for explanations/examples.
        **kwargs
            Any additional keyword arguments to be passed to
            `astropy.io.fits.open`.
            *Note:* This function automatically specifies ``do_not_scale_image_data
            = True`` when opening the file so that values can be retrieved from the
            unmodified header.
        """
        if "do_not_scale_image_data" not in kwargs:
            kwargs["do_not_scale_image_data"] = True

        closed = fileobj_closed(filename)
        hdulist, extidx = _getext(filename, "update", *args, **kwargs)
        try:
            if keyword in hdulist[extidx].header and savecomment:
                comment = None
            hdulist[extidx].header.set(keyword, value, comment, before, after)
        finally:
            hdulist.close(closed=closed)

    def delval(filename, keyword, *args, **kwargs):
        """
        Delete all instances of keyword from a header in a FITS file.

        Parameters
        ----------
        filename : path-like or file-like
            Name of the FITS file, or file object If opened, mode must be update
            (rb+).  An opened file object or `~gzip.GzipFile` object will be closed
            upon return.

        keyword : str, int
            Keyword name or index

        ext, extname, extver
            The rest of the arguments are for HDU specification.
            See `getdata` for explanations/examples.
        **kwargs
            Any additional keyword arguments to be passed to
            `astropy.io.fits.open`.
            *Note:* This function automatically specifies ``do_not_scale_image_data
            = True`` when opening the file so that values can be retrieved from the
            unmodified header.
        """
        if "do_not_scale_image_data" not in kwargs:
            kwargs["do_not_scale_image_data"] = True

        closed = fileobj_closed(filename)
        hdulist, extidx = _getext(filename, "update", *args, **kwargs)
        try:
            del hdulist[extidx].header[keyword]
        finally:
            hdulist.close(closed=closed)

    def writeto(
        filename,
        data,
        header=None,
        output_verify="exception",
        overwrite=False,
        checksum=False,
    ):
        """
        Create a new FITS file using the supplied data/header.

        Parameters
        ----------
        filename : path-like or file-like
            File to write to.  If opened, must be opened in a writable binary
            mode such as 'wb' or 'ab+'.

        data : array or `~numpy.recarray` or `~astropy.io.fits.Group`
            data to write to the new file

        header : `Header` object, optional
            the header associated with ``data``. If `None`, a header
            of the appropriate type is created for the supplied data. This
            argument is optional.

        output_verify : str
            Output verification option.  Must be one of ``"fix"``, ``"silentfix"``,
            ``"ignore"``, ``"warn"``, or ``"exception"``.  May also be any
            combination of ``"fix"`` or ``"silentfix"`` with ``"+ignore"``,
            ``+warn``, or ``+exception" (e.g. ``"fix+warn"``).  See
            :ref:`astropy:verify` for more info.

        overwrite : bool, optional
            If ``True``, overwrite the output file if it exists. Raises an
            ``OSError`` if ``False`` and the output file exists. Default is
            ``False``.

        checksum : bool, optional
            If `True`, adds both ``DATASUM`` and ``CHECKSUM`` cards to the
            headers of all HDU's written to the file.

        Notes
        -----
        gzip, zip, bzip2 and lzma compression algorithms are natively supported.
        Compression mode is determined from the filename extension
        ('.gz', '.zip', '.bz2' or '.xz' respectively).  It is also possible to pass
        a compressed file object, e.g. `gzip.GzipFile`.
        """
        hdu = _makehdu(data, header)
        if hdu.is_image and not isinstance(hdu, PrimaryHDU):
            hdu = PrimaryHDU(data, header=header)
        hdu.writeto(
            filename, overwrite=overwrite, output_verify=output_verify, checksum=checksum
        )

    def table_to_hdu(table, character_as_bytes=False, name=None):
        """
        Convert an `~astropy.table.Table` object to a FITS
        `~astropy.io.fits.BinTableHDU`.

        Parameters
        ----------
        table : astropy.table.Table
            The table to convert.
        character_as_bytes : bool
            Whether to return bytes for string columns when accessed from the HDU.
            By default this is `False` and (unicode) strings are returned, but for
            large tables this may use up a lot of memory.
        name : str
            Name to be populated in ``EXTNAME`` keyword.

        Returns
        -------
        table_hdu : `~astropy.io.fits.BinTableHDU`
            The FITS binary table HDU.
        """
        # Avoid circular imports
        from .column import python_to_tdisp
        from .connect import REMOVE_KEYWORDS, is_column_keyword

        # Header to store Time related metadata
        hdr = None

        # Not all tables with mixin columns are supported
        if table.has_mixin_columns:
            # Import is done here, in order to avoid it at build time as erfa is not
            # yet available then.
            from astropy.table.column import BaseColumn
            from astropy.time import Time
            from astropy.units import Quantity

            from .fitstime import time_to_fits

            # Only those columns which are instances of BaseColumn, Quantity or Time can
            # be written
            unsupported_cols = table.columns.not_isinstance((BaseColumn, Quantity, Time))
            if unsupported_cols:
                unsupported_names = [col.info.name for col in unsupported_cols]
                raise ValueError(
                    f"cannot write table with mixin column(s) {unsupported_names}"
                )

            time_cols = table.columns.isinstance(Time)
            if time_cols:
                table, hdr = time_to_fits(table)

        # Create a new HDU object
        tarray = table.as_array()
        if isinstance(tarray, np.ma.MaskedArray):
            # Fill masked values carefully:
            # float column's default mask value needs to be Nan and
            # string column's default mask should be an empty string.
            # Note: getting the fill value for the structured array is
            # more reliable than for individual columns for string entries.
            # (no 'N/A' for a single-element string, where it should be 'N').
            default_fill_value = np.ma.default_fill_value(tarray.dtype)
            for colname, (coldtype, _) in tarray.dtype.fields.items():
                if np.all(tarray.fill_value[colname] == default_fill_value[colname]):
                    # Since multi-element columns with dtypes such as '2f8' have
                    # a subdtype, we should look up the type of column on that.
                    coltype = (
                        coldtype.subdtype[0].type if coldtype.subdtype else coldtype.type
                    )
                    if issubclass(coltype, np.complexfloating):
                        tarray.fill_value[colname] = complex(np.nan, np.nan)
                    elif issubclass(coltype, np.inexact):
                        tarray.fill_value[colname] = np.nan
                    elif issubclass(coltype, np.character):
                        tarray.fill_value[colname] = ""

            # TODO: it might be better to construct the FITS table directly from
            # the Table columns, rather than go via a structured array.
            table_hdu = BinTableHDU.from_columns(
                tarray.filled(), header=hdr, character_as_bytes=character_as_bytes
            )
            for col in table_hdu.columns:
                # Binary FITS tables support TNULL *only* for integer data columns
                # TODO: Determine a schema for handling non-integer masked columns
                # with non-default fill values in FITS (if at all possible).
                # Be careful that we do not set null for columns that were not masked!
                int_formats = ("B", "I", "J", "K")
                if (
                    col.format.format in int_formats or col.format.p_format in int_formats
                ) and hasattr(table[col.name], "mask"):
                    fill_value = tarray[col.name].fill_value
                    col.null = fill_value.astype(int)
        else:
            table_hdu = BinTableHDU.from_columns(
                tarray, header=hdr, character_as_bytes=character_as_bytes
            )

        if name is not None:
            table_hdu.name = name

        # Set units and format display for output HDU
        for col in table_hdu.columns:
            if table[col.name].info.format is not None:
                # check for boolean types, special format case
                logical = table[col.name].info.dtype == bool

                tdisp_format = python_to_tdisp(
                    table[col.name].info.format, logical_dtype=logical
                )
                if tdisp_format is not None:
                    col.disp = tdisp_format

            unit = table[col.name].unit
            if unit is not None:
                # Local imports to avoid importing units when it is not required,
                # e.g. for command-line scripts
                from astropy.units import Unit
                from astropy.units.format.fits import UnitScaleError

                try:
                    col.unit = unit.to_string(format="fits")
                except UnitScaleError:
                    scale = unit.scale
                    raise UnitScaleError(
                        f"The column '{col.name}' could not be stored in FITS "
                        f"format because it has a scale '({str(scale)})' that "
                        "is not recognized by the FITS standard. Either scale "
                        "the data or change the units."
                    )
                except ValueError:
                    # Warn that the unit is lost, but let the details depend on
                    # whether the column was serialized (because it was a
                    # quantity), since then the unit can be recovered by astropy.
                    warning = (
                        f"The unit '{unit.to_string()}' could not be saved in "
                        "native FITS format "
                    )
                    if any(
                        "SerializedColumn" in item and "name: " + col.name in item
                        for item in table.meta.get("comments", [])
                    ):
                        warning += (
                            "and hence will be lost to non-astropy fits readers. "
                            "Within astropy, the unit can roundtrip using QTable, "
                            "though one has to enable the unit before reading."
                        )
                    else:
                        warning += (
                            "and cannot be recovered in reading. It can roundtrip "
                            "within astropy by using QTable both to write and read "
                            "back, though one has to enable the unit before reading."
                        )
                    warnings.warn(warning, AstropyUserWarning)

                else:
                    # Try creating a Unit to issue a warning if the unit is not
                    # FITS compliant
                    Unit(col.unit, format="fits", parse_strict="warn")

        # Column-specific override keywords for coordinate columns
        coord_meta = table.meta.pop("__coordinate_columns__", {})
        for col_name, col_info in coord_meta.items():
            col = table_hdu.columns[col_name]
            # Set the column coordinate attributes from data saved earlier.
            # Note: have to set these, even if we have no data.
            for attr in "coord_type", "coord_unit":
                setattr(col, attr, col_info.get(attr, None))
            trpos = col_info.get("time_ref_pos", None)
            if trpos is not None:
                col.time_ref_pos = trpos

        for key, value in table.meta.items():
            if is_column_keyword(key.upper()) or key.upper() in REMOVE_KEYWORDS:
                warnings.warn(
                    f"Meta-data keyword {key} will be ignored since it conflicts "
                    "with a FITS reserved keyword",
                    AstropyUserWarning,
                )
                continue

            # Convert to FITS format
            if key == "comments":
                key = "comment"

            if isinstance(value, list):
                for item in value:
                    try:
                        table_hdu.header.append((key, item))
                    except ValueError:
                        warnings.warn(
                            f"Attribute `{key}` of type {type(value)} cannot be "
                            "added to FITS Header - skipping",
                            AstropyUserWarning,
                        )
            else:
                try:
                    table_hdu.header[key] = value
                except ValueError:
                    warnings.warn(
                        f"Attribute `{key}` of type {type(value)} cannot be "
                        "added to FITS Header - skipping",
                        AstropyUserWarning,
                    )
        return table_hdu

    def append(filename, data, header=None, checksum=False, verify=True, **kwargs):
        """
        Append the header/data to FITS file if filename exists, create if not.

        If only ``data`` is supplied, a minimal header is created.

        Parameters
        ----------
        filename : path-like or file-like
            File to write to.  If opened, must be opened for update (rb+) unless it
            is a new file, then it must be opened for append (ab+).  A file or
            `~gzip.GzipFile` object opened for update will be closed after return.

        data : array, :class:`~astropy.table.Table`, or `~astropy.io.fits.Group`
            The new data used for appending.

        header : `Header` object, optional
            The header associated with ``data``.  If `None`, an appropriate header
            will be created for the data object supplied.

        checksum : bool, optional
            When `True` adds both ``DATASUM`` and ``CHECKSUM`` cards to the header
            of the HDU when written to the file.

        verify : bool, optional
            When `True`, the existing FITS file will be read in to verify it for
            correctness before appending.  When `False`, content is simply appended
            to the end of the file.  Setting ``verify`` to `False` can be much
            faster.

        **kwargs
            Additional arguments are passed to:

            - `~astropy.io.fits.writeto` if the file does not exist or is empty.
              In this case ``output_verify`` is the only possible argument.
            - `~astropy.io.fits.open` if ``verify`` is True or if ``filename``
              is a file object.
            - Otherwise no additional arguments can be used.

        """
        if isinstance(filename, path_like):
            filename = os.path.expanduser(filename)
        name, closed, noexist_or_empty = _stat_filename_or_fileobj(filename)

        if noexist_or_empty:
            #
            # The input file or file like object either doesn't exits or is
            # empty.  Use the writeto convenience function to write the
            # output to the empty object.
            #
            writeto(filename, data, header, checksum=checksum, **kwargs)
        else:
            hdu = _makehdu(data, header)

            if isinstance(hdu, PrimaryHDU):
                hdu = ImageHDU(data, header)

            if verify or not closed:
                f = fitsopen(filename, mode="append", **kwargs)
                try:
                    f.append(hdu)

                    # Set a flag in the HDU so that only this HDU gets a checksum
                    # when writing the file.
                    hdu._output_checksum = checksum
                finally:
                    f.close(closed=closed)
            else:
                f = _File(filename, mode="append")
                try:
                    hdu._output_checksum = checksum
                    hdu._writeto(f)
                finally:
                    f.close()

    def update(filename, data, *args, **kwargs):
        """
        Update the specified HDU with the input data/header.

        Parameters
        ----------
        filename : path-like or file-like
            File to update.  If opened, mode must be update (rb+).  An opened file
            object or `~gzip.GzipFile` object will be closed upon return.

        data : array, `~astropy.table.Table`, or `~astropy.io.fits.Group`
            The new data used for updating.

        header : `Header` object, optional
            The header associated with ``data``.  If `None`, an appropriate header
            will be created for the data object supplied.

        ext, extname, extver
            The rest of the arguments are flexible: the 3rd argument can be the
            header associated with the data.  If the 3rd argument is not a
            `Header`, it (and other positional arguments) are assumed to be the
            HDU specification(s).  Header and HDU specs can also be
            keyword arguments.  For example::

                update(file, dat, hdr, 'sci')  # update the 'sci' extension
                update(file, dat, 3)  # update the 3rd extension HDU
                update(file, dat, hdr, 3)  # update the 3rd extension HDU
                update(file, dat, 'sci', 2)  # update the 2nd extension HDU named 'sci'
                update(file, dat, 3, header=hdr)  # update the 3rd extension HDU
                update(file, dat, header=hdr, ext=5)  # update the 5th extension HDU

        **kwargs
            Any additional keyword arguments to be passed to
            `astropy.io.fits.open`.
        """
        # The arguments to this function are a bit trickier to deal with than others
        # in this module, since the documentation has promised that the header
        # argument can be an optional positional argument.
        if args and isinstance(args[0], Header):
            header = args[0]
            args = args[1:]
        else:
            header = None
        # The header can also be a keyword argument--if both are provided the
        # keyword takes precedence
        header = kwargs.pop("header", header)

        new_hdu = _makehdu(data, header)

        closed = fileobj_closed(filename)

        hdulist, _ext = _getext(filename, "update", *args, **kwargs)
        try:
            hdulist[_ext] = new_hdu
        finally:
            hdulist.close(closed=closed)

    def info(filename, output=None, **kwargs):
        """
        Print the summary information on a FITS file.

        This includes the name, type, length of header, data shape and type
        for each HDU.

        Parameters
        ----------
        filename : path-like or file-like
            FITS file to obtain info from.  If opened, mode must be one of
            the following: rb, rb+, or ab+ (i.e. the file must be readable).

        output : file, bool, optional
            A file-like object to write the output to.  If ``False``, does not
            output to a file and instead returns a list of tuples representing the
            HDU info.  Writes to ``sys.stdout`` by default.
        **kwargs
            Any additional keyword arguments to be passed to
            `astropy.io.fits.open`.
            *Note:* This function sets ``ignore_missing_end=True`` by default.
        """
        mode, closed = _get_file_mode(filename, default="readonly")
        # Set the default value for the ignore_missing_end parameter
        if "ignore_missing_end" not in kwargs:
            kwargs["ignore_missing_end"] = True

        f = fitsopen(filename, mode=mode, **kwargs)
        try:
            ret = f.info(output=output)
        finally:
            if closed:
                f.close()

        return ret

    def printdiff(inputa, inputb, *args, **kwargs):
        """
        Compare two parts of a FITS file, including entire FITS files,
        FITS `HDUList` objects and FITS ``HDU`` objects.

        Parameters
        ----------
        inputa : str, `HDUList` object, or ``HDU`` object
            The filename of a FITS file, `HDUList`, or ``HDU``
            object to compare to ``inputb``.

        inputb : str, `HDUList` object, or ``HDU`` object
            The filename of a FITS file, `HDUList`, or ``HDU``
            object to compare to ``inputa``.

        ext, extname, extver
            Additional positional arguments are for HDU specification if your
            inputs are string filenames (will not work if
            ``inputa`` and ``inputb`` are ``HDU`` objects or `HDUList` objects).
            They are flexible and are best illustrated by examples.  In addition
            to using these arguments positionally you can directly call the
            keyword parameters ``ext``, ``extname``.

            By HDU number::

                printdiff('inA.fits', 'inB.fits', 0)      # the primary HDU
                printdiff('inA.fits', 'inB.fits', 2)      # the second extension HDU
                printdiff('inA.fits', 'inB.fits', ext=2)  # the second extension HDU

            By name, i.e., ``EXTNAME`` value (if unique). ``EXTNAME`` values are
            not case sensitive:

                printdiff('inA.fits', 'inB.fits', 'sci')
                printdiff('inA.fits', 'inB.fits', extname='sci')  # equivalent

            By combination of ``EXTNAME`` and ``EXTVER`` as separate
            arguments or as a tuple::

                printdiff('inA.fits', 'inB.fits', 'sci', 2)    # EXTNAME='SCI'
                                                               # & EXTVER=2
                printdiff('inA.fits', 'inB.fits', extname='sci', extver=2)
                                                               # equivalent
                printdiff('inA.fits', 'inB.fits', ('sci', 2))  # equivalent

            Ambiguous or conflicting specifications will raise an exception::

                printdiff('inA.fits', 'inB.fits',
                          ext=('sci', 1), extname='err', extver=2)

        **kwargs
            Any additional keyword arguments to be passed to
            `~astropy.io.fits.FITSDiff`.

        Notes
        -----
        The primary use for the `printdiff` function is to allow quick print out
        of a FITS difference report and will write to ``sys.stdout``.
        To save the diff report to a file please use `~astropy.io.fits.FITSDiff`
        directly.
        """
        # Pop extension keywords
        extension = {
            key: kwargs.pop(key) for key in ["ext", "extname", "extver"] if key in kwargs
        }
        has_extensions = args or extension

        if isinstance(inputa, str) and has_extensions:
            # Use handy _getext to interpret any ext keywords, but
            # will need to close a if  fails
            modea, closeda = _get_file_mode(inputa)
            modeb, closedb = _get_file_mode(inputb)

            hdulista, extidxa = _getext(inputa, modea, *args, **extension)
            # Have to close a if b doesn't make it
            try:
                hdulistb, extidxb = _getext(inputb, modeb, *args, **extension)
            except Exception:
                hdulista.close(closed=closeda)
                raise

            try:
                hdua = hdulista[extidxa]
                hdub = hdulistb[extidxb]
                # See below print for note
                print(HDUDiff(hdua, hdub, **kwargs).report())

            finally:
                hdulista.close(closed=closeda)
                hdulistb.close(closed=closedb)

        # If input is not a string, can feed HDU objects or HDUList directly,
        # but can't currently handle extensions
        elif isinstance(inputa, _ValidHDU) and has_extensions:
            raise ValueError("Cannot use extension keywords when providing an HDU object.")

        elif isinstance(inputa, _ValidHDU) and not has_extensions:
            print(HDUDiff(inputa, inputb, **kwargs).report())

        elif isinstance(inputa, HDUList) and has_extensions:
            raise NotImplementedError(
                "Extension specification with HDUList objects not implemented."
            )

        # This function is EXCLUSIVELY for printing the diff report to screen
        # in a one-liner call, hence the use of print instead of logging
        else:
            print(FITSDiff(inputa, inputb, **kwargs).report())

    def tabledump(filename, datafile=None, cdfile=None, hfile=None, ext=1, overwrite=False):
        """
        Dump a table HDU to a file in ASCII format.  The table may be
        dumped in three separate files, one containing column definitions,
        one containing header parameters, and one for table data.

        Parameters
        ----------
        filename : path-like or file-like
            Input fits file.

        datafile : path-like or file-like, optional
            Output data file.  The default is the root name of the input
            fits file appended with an underscore, followed by the
            extension number (ext), followed by the extension ``.txt``.

        cdfile : path-like or file-like, optional
            Output column definitions file.  The default is `None`,
            no column definitions output is produced.

        hfile : path-like or file-like, optional
            Output header parameters file.  The default is `None`,
            no header parameters output is produced.

        ext : int
            The number of the extension containing the table HDU to be
            dumped.

        overwrite : bool, optional
            If ``True``, overwrite the output file if it exists. Raises an
            ``OSError`` if ``False`` and the output file exists. Default is
            ``False``.

        Notes
        -----
        The primary use for the `tabledump` function is to allow editing in a
        standard text editor of the table data and parameters.  The
        `tableload` function can be used to reassemble the table from the
        three ASCII files.
        """
        # allow file object to already be opened in any of the valid modes
        # and leave the file in the same state (opened or closed) as when
        # the function was called

        mode, closed = _get_file_mode(filename, default="readonly")
        f = fitsopen(filename, mode=mode)

        # Create the default data file name if one was not provided
        try:
            if not datafile:
                root, tail = os.path.splitext(f._file.name)
                datafile = root + "_" + repr(ext) + ".txt"

            # Dump the data from the HDU to the files
            f[ext].dump(datafile, cdfile, hfile, overwrite)
        finally:
            if closed:
                f.close()

    if isinstance(tabledump.__doc__, str):
        tabledump.__doc__ += BinTableHDU._tdump_file_format.replace("\n", "\n    ")

    def tableload(datafile, cdfile, hfile=None):
        """
        Create a table from the input ASCII files.  The input is from up
        to three separate files, one containing column definitions, one
        containing header parameters, and one containing column data.  The
        header parameters file is not required.  When the header
        parameters file is absent a minimal header is constructed.

        Parameters
        ----------
        datafile : path-like or file-like
            Input data file containing the table data in ASCII format.

        cdfile : path-like or file-like
            Input column definition file containing the names, formats,
            display formats, physical units, multidimensional array
            dimensions, undefined values, scale factors, and offsets
            associated with the columns in the table.

        hfile : path-like or file-like, optional
            Input parameter definition file containing the header
            parameter definitions to be associated with the table.
            If `None`, a minimal header is constructed.

        Notes
        -----
        The primary use for the `tableload` function is to allow the input of
        ASCII data that was edited in a standard text editor of the table
        data and parameters.  The tabledump function can be used to create the
        initial ASCII files.
        """
        return BinTableHDU.load(datafile, cdfile, hfile, replace=True)

    if isinstance(tableload.__doc__, str):
        tableload.__doc__ += BinTableHDU._tdump_file_format.replace("\n", "\n    ")

    def _getext(filename, mode, *args, ext=None, extname=None, extver=None, **kwargs):
        """
        Open the input file, return the `HDUList` and the extension.

        This supports several different styles of extension selection.  See the
        :func:`getdata()` documentation for the different possibilities.
        """
        err_msg = "Redundant/conflicting extension arguments(s): {}".format(
            {"args": args, "ext": ext, "extname": extname, "extver": extver}
        )

        # This code would be much simpler if just one way of specifying an
        # extension were picked.  But now we need to support all possible ways for
        # the time being.
        if len(args) == 1:
            # Must be either an extension number, an extension name, or an
            # (extname, extver) tuple
            if _is_int(args[0]) or (isinstance(ext, tuple) and len(ext) == 2):
                if ext is not None or extname is not None or extver is not None:
                    raise TypeError(err_msg)
                ext = args[0]
            elif isinstance(args[0], str):
                # The first arg is an extension name; it could still be valid
                # to provide an extver kwarg
                if ext is not None or extname is not None:
                    raise TypeError(err_msg)
                extname = args[0]
            else:
                # Take whatever we have as the ext argument; we'll validate it
                # below
                ext = args[0]
        elif len(args) == 2:
            # Must be an extname and extver
            if ext is not None or extname is not None or extver is not None:
                raise TypeError(err_msg)
            extname = args[0]
            extver = args[1]
        elif len(args) > 2:
            raise TypeError("Too many positional arguments.")

        if ext is not None and not (
            _is_int(ext)
            or (
                isinstance(ext, tuple)
                and len(ext) == 2
                and isinstance(ext[0], str)
                and _is_int(ext[1])
            )
        ):
            raise ValueError(
                "The ext keyword must be either an extension number "
                "(zero-indexed) or a (extname, extver) tuple."
            )
        if extname is not None and not isinstance(extname, str):
            raise ValueError("The extname argument must be a string.")
        if extver is not None and not _is_int(extver):
            raise ValueError("The extver argument must be an integer.")

        if ext is None and extname is None and extver is None:
            ext = 0
        elif ext is not None and (extname is not None or extver is not None):
            raise TypeError(err_msg)
        elif extname:
            if extver:
                ext = (extname, extver)
            else:
                ext = (extname, 1)
        elif extver and extname is None:
            raise TypeError("extver alone cannot specify an extension.")

        hdulist = fitsopen(filename, mode=mode, **kwargs)

        return hdulist, ext

    def _makehdu(data, header):
        if header is None:
            header = Header()
        hdu = _BaseHDU._from_data(data, header)
        if hdu.__class__ in (_BaseHDU, _ValidHDU):
            # The HDU type was unrecognized, possibly due to a
            # nonexistent/incomplete header
            if (
                isinstance(data, np.ndarray) and data.dtype.fields is not None
            ) or isinstance(data, np.recarray):
                hdu = BinTableHDU(data, header=header)
            elif isinstance(data, np.ndarray) or _is_dask_array(data):
                hdu = ImageHDU(data, header=header)
            else:
                raise KeyError("Data must be a numpy array.")
        return hdu

    def _stat_filename_or_fileobj(filename):
        if isinstance(filename, os.PathLike):
            filename = os.fspath(filename)
        closed = fileobj_closed(filename)
        name = fileobj_name(filename) or ""

        try:
            loc = filename.tell()
        except AttributeError:
            loc = 0

        noexist_or_empty = (
            name and (not os.path.exists(name) or (os.path.getsize(name) == 0))
        ) or (not name and loc == 0)

        return name, closed, noexist_or_empty

    def _get_file_mode(filename, default="readonly"):
        """
        Allow file object to already be opened in any of the valid modes and
        and leave the file in the same state (opened or closed) as when
        the function was called.
        """
        mode = default
        closed = fileobj_closed(filename)

        fmode = fileobj_mode(filename)
        if fmode is not None:
            mode = FILE_MODES.get(fmode)
            if mode is None:
                raise OSError(
                    f"File mode of the input file object ({fmode!r}) cannot be used to "
                    "read/write FITS files."
                )

        return mode, closed