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# Source code for astropy.io.fits.card

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

    import copy
    import re
    import warnings

    import numpy as np

    from .util import _str_to_num, _is_int, maketrans, translate, _words_group
    from .verify import _Verify, _ErrList, VerifyError, VerifyWarning

    from . import conf
    from ...extern.six import string_types, integer_types, text_type, binary_type
    from ...utils import deprecated
    from ...utils.exceptions import AstropyUserWarning, AstropyDeprecationWarning

    __all__ = ['Card', 'CardList', 'create_card', 'create_card_from_string',
               'upper_key', 'Undefined']

    FIX_FP_TABLE = maketrans('de', 'DE')
    FIX_FP_TABLE2 = maketrans('dD', 'eE')

    CARD_LENGTH = 80
    BLANK_CARD = ' ' * CARD_LENGTH
    KEYWORD_LENGTH = 8  # The max length for FITS-standard keywords

    VALUE_INDICATOR = '= '  # The standard FITS value indicator
    HIERARCH_VALUE_INDICATOR = '='  # HIERARCH cards may use a shortened indicator

    class Undefined(object):
        """Undefined value."""

        def __init__(self):
            # This __init__ is required to be here for Sphinx documentation
            pass
    UNDEFINED = Undefined()

    class CardList(list):
        """
        .. deprecated:: 0.1
            `CardList` used to provide the list-like functionality for manipulating
            a header as a list of cards.  This functionality is now subsumed into
            the `Header` class itself, so it is no longer necessary to create or
            use `CardList`\s.
        """

        def __init__(self, cards=[], keylist=None):
            """
            Construct the `CardList` object from a list of `Card` objects.

            `CardList` is now merely a thin wrapper around `Header` to provide
            backwards compatibility for the old API.  This should not be used for
            any new code.

            Parameters
            ----------
            cards
                A list of `Card` objects.
            """

            warnings.warn(
                    'The CardList class has been deprecated; all its former '
                    'functionality has been subsumed by the Header class, so '
                    'CardList objects should not be directly created.  See the '
                    'PyFITS 3.1.0 CHANGELOG for more details.',
                    AstropyDeprecationWarning)

            # This is necessary for now to prevent a circular import
            from .header import Header

            # I'm not sure if they keylist argument here was ever really useful;
            # I'm going to just say don't use it.
            if keylist is not None:
                raise ValueError(
                    'The keylist argument to CardList() is no longer supported.')

            if isinstance(cards, Header):
                self._header = cards
            else:
                self._header = Header(cards)

            super(CardList, self).__init__(self._header.cards)

        def __contains__(self, key):
            return key in self._header

        def __iter__(self):
            return iter(self._header.cards)

        def __getitem__(self, key):
            """Get a `Card` by indexing or by the keyword name."""

            if self._header._haswildcard(key):
                return [copy.copy(self._header._cards[idx])
                        for idx in self._header._wildcardmatch(key)]
            elif isinstance(key, slice):
                return CardList(self._header.cards[key])

            idx = self._header._cardindex(key)
            return self._header.cards[idx]

        def __setitem__(self, key, value):
            """Set a `Card` by indexing or by the keyword name."""

            if isinstance(value, tuple) and (1 < len(value) <= 3):
                value = Card(*value)

            if isinstance(value, Card):
                idx = self._header._cardindex(key)
                card = self._header.cards[idx]
                if str(card) != str(value):
                    # Replace the existing card at this index by delete/insert
                    del self._header[idx]
                    self._header.insert(idx, value)
            else:
                raise ValueError('%s is not a Card' % str(value))

        def __delitem__(self, key):
            """Delete a `Card` from the `CardList`."""

            if key not in self._header._keyword_indices:
                raise KeyError("Keyword '%s' not found." % key)
            del self._header[key]

        def __getslice__(self, start, end):
            return CardList(self[slice(start, end)])

        def __repr__(self):
            """Format a list of cards into a string."""

            return str(self._header)

        def __str__(self):
            """Format a list of cards into a printable string."""

            return '\n'.join(str(card) for card in self)

        @deprecated('0.1', alternative=':meth:`Header.copy`', pending=False)
        def copy(self):
            """Make a (deep)copy of the `CardList`."""

            return CardList(self._header.copy())

        @deprecated('0.1', alternative=':meth:`Header.keys`', pending=False)
        def keys(self):
            """
            Return a list of all keywords from the `CardList`.
            """

            return self._header.keys()

        @deprecated('0.1', alternative=':meth:`Header.values`', pending=False)
        def values(self):
            """
            Return a list of the values of all cards in the `CardList`.

            For ``RecordValuedKeywordCard`` objects, the value returned is
            the floating point value, exclusive of the
            ``field_specifier``.
            """

            return self._header.values()

        @deprecated('0.1', alternative=':meth:`Header.append`', pending=False)
        def append(self, card, useblanks=True, bottom=False):
            """
            Append a `Card` to the `CardList`.

            Parameters
            ----------
            card : `Card` object
                The `Card` to be appended.

            useblanks : bool, optional
                Use any *extra* blank cards?

                If ``useblanks`` is `True`, and if there are blank cards directly
                before ``END``, it will use this space first, instead of appending
                after these blank cards, so the total space will not increase.
                When ``useblanks`` is `False`, the card will be appended at the
                end, even if there are blank cards in front of ``END``.

            bottom : bool, optional
               If `False` the card will be appended after the last non-commentary
               card.  If `True` the card will be appended after the last non-blank
               card.
            """

            self._header.append(card, useblanks=useblanks, bottom=bottom)

        @deprecated('0.1', alternative=':meth:`Header.extend`', pending=False)
        def extend(self, cards):
            self._header.extend(cards)

        @deprecated('0.1', alternative=':meth:`Header.insert`', pending=False)
        def insert(self, idx, card, useblanks=True):
            """
            Insert a `Card` to the `CardList`.

            Parameters
            ----------
            pos : int
                The position (index, keyword name will not be allowed) to
                insert. The new card will be inserted before it.

            card : `Card` object
                The card to be inserted.

            useblanks : bool, optional
                If ``useblanks`` is `True`, and if there are blank cards directly
                before ``END``, it will use this space first, instead of appending
                after these blank cards, so the total space will not increase.
                When ``useblanks`` is `False`, the card will be appended at the end,
                even if there are blank cards in front of ``END``.
            """

            self._header.insert(idx, card, useblanks=useblanks)

        @deprecated('0.1', alternative=':meth:`Header.remove`')
        def remove(self, card):
            del self._header[self.index(card)]

        @deprecated('0.1', alternative=':meth:`Header.pop`')
        def pop(self, index=-1):
            return self._header.pop(index)

        @deprecated('0.1', alternative=':meth:`Header.index`')
        def index(self, card):
            return self._header._cards.index(card)

        @deprecated('0.1', alternative=':meth:`Header.count`')
        def count(self, card):
            return self._header._cards.count(card)

        @deprecated('0.1', alternative=':meth:`Header.index`', pending=False)
        def index_of(self, key, backward=False):
            """
            Get the index of a keyword in the `CardList`.

            Parameters
            ----------
            key : str or int
                The keyword name (a string) or the index (an integer).

            backward : bool, optional
                When `True`, search the index from the ``END``, i.e.,
                backward.

            Returns
            -------
            index : int
                The index of the `Card` with the given keyword.
            """

            # Backward is just ignored now, since the search is not linear anyways

            if _is_int(key) or isinstance(key, string_types):
                return self._header._cardindex(key)
            else:
                raise KeyError('Illegal key data type %s' % type(key))

        @deprecated('0.1', alternative='``header[<wildcard_pattern>]``')
        def filter_list(self, key):
            """
            Construct a `CardList` that contains references to all of the cards in
            this `CardList` that match the input key value including any special
            filter keys (``*``, ``?``, and ``...``).

            Parameters
            ----------
            key : str
                key value to filter the list with

            Returns
            -------
            cardlist
                A `CardList` object containing references to all the
                requested cards.
            """

            return CardList(self._header[key])

        @deprecated('0.1', pending=False)
        def count_blanks(self):
            """
            Returns how many blank cards are *directly* before the ``END``
            card.
            """

            return self._header._countblanks()

    class Card(_Verify):

        length = CARD_LENGTH
        """The length of a Card image; should always be 80 for valid FITS files."""

        # String for a FITS standard compliant (FSC) keyword.
        _keywd_FSC_RE = re.compile(r'^[A-Z0-9_-]{0,%d}$' % KEYWORD_LENGTH)
        # This will match any printable ASCII character excluding '='
        _keywd_hierarch_RE = re.compile(r'^(?:HIERARCH +)?(?:^[ -<>-~]+ ?)+$',
                                        re.I)

        # A number sub-string, either an integer or a float in fixed or
        # scientific notation.  One for FSC and one for non-FSC (NFSC) format:
        # NFSC allows lower case of DE for exponent, allows space between sign,
        # digits, exponent sign, and exponents
        _digits_FSC = r'(\.\d+|\d+(\.\d*)?)([DE][+-]?\d+)?'
        _digits_NFSC = r'(\.\d+|\d+(\.\d*)?) *([deDE] *[+-]? *\d+)?'
        _numr_FSC = r'[+-]?' + _digits_FSC
        _numr_NFSC = r'[+-]? *' + _digits_NFSC

        # This regex helps delete leading zeros from numbers, otherwise
        # Python might evaluate them as octal values (this is not-greedy, however,
        # so it may not strip leading zeros from a float, which is fine)
        _number_FSC_RE = re.compile(r'(?P<sign>[+-])?0*?(?P<digt>%s)'
                                    % _digits_FSC)
        _number_NFSC_RE = re.compile(r'(?P<sign>[+-])? *0*?(?P<digt>%s)'
                                     % _digits_NFSC)

        # FSC commentary card string which must contain printable ASCII characters.
        # Note: \Z matches the end of the string without allowing newlines
        _ascii_text_re = re.compile(r'[ -~]*\Z')

        # Checks for a valid value/comment string.  It returns a match object
        # for a valid value/comment string.
        # The valu group will return a match if a FITS string, boolean,
        # number, or complex value is found, otherwise it will return
        # None, meaning the keyword is undefined.  The comment field will
        # return a match if the comment separator is found, though the
        # comment maybe an empty string.
        _value_FSC_RE = re.compile(
            r'(?P<valu_field> *'
                r'(?P<valu>'

                    #  The <strg> regex is not correct for all cases, but
                    #  it comes pretty darn close.  It appears to find the
                    #  end of a string rather well, but will accept
                    #  strings with an odd number of single quotes,
                    #  instead of issuing an error.  The FITS standard
                    #  appears vague on this issue and only states that a
                    #  string should not end with two single quotes,
                    #  whereas it should not end with an even number of
                    #  quotes to be precise.
                    #
                    #  Note that a non-greedy match is done for a string,
                    #  since a greedy match will find a single-quote after
                    #  the comment separator resulting in an incorrect
                    #  match.
                    r'\'(?P<strg>([ -~]+?|\'\'|)) *?\'(?=$|/| )|'
                    r'(?P<bool>[FT])|'
                    r'(?P<numr>' + _numr_FSC + r')|'
                    r'(?P<cplx>\( *'
                        r'(?P<real>' + _numr_FSC + r') *, *'
                        r'(?P<imag>' + _numr_FSC + r') *\))'
                r')? *)'
            r'(?P<comm_field>'
                r'(?P<sepr>/ *)'
                r'(?P<comm>[!-~][ -~]*)?'
            r')?$')

        _value_NFSC_RE = re.compile(
            r'(?P<valu_field> *'
                r'(?P<valu>'
                    r'\'(?P<strg>([ -~]+?|\'\'|) *?)\'(?=$|/| )|'
                    r'(?P<bool>[FT])|'
                    r'(?P<numr>' + _numr_NFSC + r')|'
                    r'(?P<cplx>\( *'
                        r'(?P<real>' + _numr_NFSC + r') *, *'
                        r'(?P<imag>' + _numr_NFSC + r') *\))'
                r')? *)'
            r'(?P<comm_field>'
                r'(?P<sepr>/ *)'
                r'(?P<comm>(.|\n)*)'
            r')?$')

        _rvkc_identifier = r'[a-zA-Z_]\w*'
        _rvkc_field = _rvkc_identifier + r'(\.\d+)?'
        _rvkc_field_specifier_s = r'%s(\.%s)*' % ((_rvkc_field,) * 2)
        _rvkc_field_specifier_val = (r'(?P<keyword>%s): (?P<val>%s)' %
                                     (_rvkc_field_specifier_s, _numr_FSC))
        _rvkc_keyword_val = r'\'(?P<rawval>%s)\'' % _rvkc_field_specifier_val
        _rvkc_keyword_val_comm = (r' *%s *(/ *(?P<comm>[ -~]*))?$' %
                                  _rvkc_keyword_val)

        _rvkc_field_specifier_val_RE = re.compile(_rvkc_field_specifier_val + '$')

        # regular expression to extract the key and the field specifier from a
        # string that is being used to index into a card list that contains
        # record value keyword cards (ex. 'DP1.AXIS.1')
        _rvkc_keyword_name_RE = (
            re.compile(r'(?P<keyword>%s)\.(?P<field_specifier>%s)$' %
                       (_rvkc_identifier, _rvkc_field_specifier_s)))

        # regular expression to extract the field specifier and value and comment
        # from the string value of a record value keyword card
        # (ex "'AXIS.1: 1' / a comment")
        _rvkc_keyword_val_comm_RE = re.compile(_rvkc_keyword_val_comm)

        _commentary_keywords = set(['', 'COMMENT', 'HISTORY', 'END'])

        # The default value indicator; may be changed if required by a convention
        # (namely HIERARCH cards)
        _value_indicator = VALUE_INDICATOR

        def __init__(self, keyword=None, value=None, comment=None, **kwargs):
            # For backwards compatibility, support the 'key' keyword argument:
            if keyword is None and 'key' in kwargs:
                keyword = kwargs['key']

            self._keyword = None
            self._value = None
            self._comment = None

            self._image = None

            # This attribute is set to False when creating the card from a card
            # image to ensure that the contents of the image get verified at some
            # point
            self._verified = True

            # A flag to conveniently mark whether or not this was a valid HIERARCH
            # card
            self._hierarch = False

            # If the card could not be parsed according the the FITS standard or
            # any recognized non-standard conventions, this will be True
            self._invalid = False

            self._field_specifier = None

            # These are used primarily only by RVKCs
            self._rawkeyword = None
            self._rawvalue = None

            if not (keyword is not None and value is not None and
                    self._check_if_rvkc(keyword, value)):
                # If _check_if_rvkc passes, it will handle setting the keyword and
                # value
                if keyword is not None:
                    self.keyword = keyword
                if value is not None:
                    self.value = value

            if comment is not None:
                self.comment = comment

            self._modified = False
            self._valuestring = None
            self._valuemodified = False

        def __repr__(self):
            return repr((self.keyword, self.value, self.comment))

        def __str__(self):
            return self.image

        def __len__(self):
            return 3

        def __getitem__(self, index):
            return (self.keyword, self.value, self.comment)[index]

        @property
        def keyword(self):
            """Returns the keyword name parsed from the card image."""
            if self._keyword is not None:
                return self._keyword
            elif self._image:
                self._keyword = self._parse_keyword()
                return self._keyword
            else:
                self.keyword = ''
                return ''

        @keyword.setter
        def keyword(self, keyword):
            """Set the key attribute; once set it cannot be modified."""
            if self._keyword is not None:
                raise AttributeError(
                    'Once set, the Card keyword may not be modified')
            elif isinstance(keyword, string_types):
                # Be nice and remove trailing whitespace--some FITS code always
                # pads keywords out with spaces; leading whitespace, however,
                # should be strictly disallowed.
                keyword = keyword.rstrip()
                keyword_upper = keyword.upper()
                if (len(keyword) <= KEYWORD_LENGTH and
                    self._keywd_FSC_RE.match(keyword_upper)):
                    # For keywords with length > 8 they will be HIERARCH cards,
                    # and can have arbitrary case keywords
                    if keyword_upper == 'END':
                        raise ValueError("Keyword 'END' not allowed.")
                    keyword = keyword_upper
                elif self._keywd_hierarch_RE.match(keyword):
                    # In prior versions of PyFITS HIERARCH cards would only be
                    # created if the user-supplied keyword explicitly started with
                    # 'HIERARCH '.  Now we will create them automatically for long
                    # keywords, but we still want to support the old behavior too;
                    # the old behavior makes it possible to create HEIRARCH cards
                    # that would otherwise be recognized as RVKCs
                    self._hierarch = True
                    self._value_indicator = HIERARCH_VALUE_INDICATOR

                    if keyword_upper[:9] == 'HIERARCH ':
                        # The user explicitly asked for a HIERARCH card, so don't
                        # bug them about it...
                        keyword = keyword[9:].strip()
                    else:
                        # We'll gladly create a HIERARCH card, but a warning is
                        # also displayed
                        warnings.warn(
                            'Keyword name %r is greater than 8 characters or '
                            'contains characters not allowed by the FITS '
                            'standard; a HIERARCH card will be created.' %
                            keyword, VerifyWarning)
                else:
                    raise ValueError('Illegal keyword name: %r.' % keyword)
                self._keyword = keyword
                self._modified = True
            else:
                raise ValueError('Keyword name %r is not a string.' % keyword)

        @property
        @deprecated('0.1', alternative='the `.keyword` attribute')
        def key(self):
            return self.keyword

        @property
        def value(self):
            """The value associated with the keyword stored in this card."""

            if self.field_specifier:
                return float(self._value)

            if self._value is not None:
                value = self._value
            elif self._valuestring is not None or self._image:
                self._value = self._parse_value()
                value = self._value
            else:
                self._value = value = ''

            if conf.strip_header_whitespace and isinstance(value, string_types):
                value = value.rstrip()

            return value

        @value.setter
        def value(self, value):
            if self._invalid:
                raise ValueError(
                    'The value of invalid/unparseable cards cannot set.  Either '
                    'delete this card from the header or replace it.')

            if value is None:
                value = ''
            oldvalue = self._value
            if oldvalue is None:
                oldvalue = ''

            if not isinstance(value, string_types + integer_types +
                                     (float, complex, bool, Undefined, np.floating,
                                      np.integer, np.complexfloating, np.bool_)):
                raise ValueError('Illegal value: %r.' % value)

            if isinstance(value, float) and (np.isnan(value) or np.isinf(value)):
                raise ValueError(
                    "Floating point %r values are not allowed in FITS headers." %
                    value)
            elif isinstance(value, text_type):
                m = self._ascii_text_re.match(value)
                if not m:
                    raise ValueError(
                        'FITS header values must contain standard printable ASCII '
                        'characters; %r contains characters not representable in '
                        'ASCII or non-printable characters.' % value)
            elif isinstance(value, binary_type):
                # Allow str, but only if they can be decoded to ASCII text; note
                # this is not even allowed on Python 3 since the `bytes` type is
                # not included in `six.string_types`.  Presently we simply don't
                # allow bytes to be assigned to headers, as doing so would too
                # easily mask potential user error
                valid = True
                try:
                    text_value = value.decode('ascii')
                except UnicodeDecodeError:
                    valid = False
                else:
                    # Check against the printable characters regexp as well
                    m = self._ascii_text_re.match(text_value)
                    valid = m is not None

                if not valid:
                    raise ValueError(
                        'FITS header values must contain standard printable ASCII '
                        'characters; %r contains characters/bytes that do not '
                        'represent printable characters in ASCII.' % value)
            elif isinstance(value, np.bool_):
                value = bool(value)

            if (conf.strip_header_whitespace and
                (isinstance(oldvalue, string_types) and
                 isinstance(value, string_types))):
                # Ignore extra whitespace when comparing the new value to the old
                different = oldvalue.rstrip() != value.rstrip()
            elif isinstance(oldvalue, bool) or isinstance(value, bool):
                different = oldvalue is not value
            else:
                different = (oldvalue != value or
                             not isinstance(value, type(oldvalue)))

            if different:
                self._value = value
                self._rawvalue = None
                self._modified = True
                self._valuestring = None
                self._valuemodified = True
                if self.field_specifier:
                    try:
                        self._value = _int_or_float(self._value)
                    except ValueError:
                        raise ValueError('value %s is not a float' %
                                         self._value)

        @value.deleter
        def value(self):
            if self._invalid:
                raise ValueError(
                    'The value of invalid/unparseable cards cannot deleted.  '
                    'Either delete this card from the header or replace it.')

            if not self.field_specifier:
                self.value = ''
            else:
                raise AttributeError('Values cannot be deleted from record-valued '
                                     'keyword cards')

        @property
        def rawkeyword(self):
            """On record-valued keyword cards this is the name of the standard <= 8
            character FITS keyword that this RVKC is stored in.  Otherwise it is
            the card's normal keyword.
            """

            if self._rawkeyword is not None:
                return self._rawkeyword
            elif self.field_specifier is not None:
                self._rawkeyword = self.keyword.split('.', 1)[0]
                return self._rawkeyword
            else:
                return self.keyword

        @property
        def rawvalue(self):
            """On record-valued keyword cards this is the raw string value in
            the ``<field-specifier>: <value>`` format stored in the card in order
            to represent a RVKC.  Otherwise it is the card's normal value.
            """

            if self._rawvalue is not None:
                return self._rawvalue
            elif self.field_specifier is not None:
                self._rawvalue = '%s: %s' % (self.field_specifier, self.value)
                return self._rawvalue
            else:
                return self.value

        @property
        def comment(self):
            """Get the comment attribute from the card image if not already set."""

            if self._comment is not None:
                return self._comment
            elif self._image:
                self._comment = self._parse_comment()
                return self._comment
            else:
                self.comment = ''
                return ''

        @comment.setter
        def comment(self, comment):
            if self._invalid:
                raise ValueError(
                    'The comment of invalid/unparseable cards cannot set.  Either '
                    'delete this card from the header or replace it.')

            if comment is None:
                comment = ''

            if isinstance(comment, text_type):
                m = self._ascii_text_re.match(comment)
                if not m:
                    raise ValueError(
                        'FITS header comments must contain standard printable '
                        'ASCII characters; %r contains characters not '
                        'representable in ASCII or non-printable characters.' %
                        comment)

            oldcomment = self._comment
            if oldcomment is None:
                oldcomment = ''
            if comment != oldcomment:
                self._comment = comment
                self._modified = True

        @comment.deleter
        def comment(self):
            if self._invalid:
                raise ValueError(
                    'The comment of invalid/unparseable cards cannot deleted.  '
                    'Either delete this card from the header or replace it.')

            self.comment = ''

        @property
        def field_specifier(self):
            """
            The field-specifier of record-valued keyword cards; always `None` on
            normal cards.
            """

            # Ensure that the keyword exists and has been parsed--the will set the
            # internal _field_specifier attribute if this is a RVKC.
            if self.keyword:
                return self._field_specifier
            else:
                return None

        @field_specifier.setter
        def field_specifier(self, field_specifier):
            if not field_specifier:
                raise ValueError('The field-specifier may not be blank in '
                                 'record-valued keyword cards.')
            elif not self.field_specifier:
                raise AttributeError('Cannot coerce cards to be record-valued '
                                     'keyword cards by setting the '
                                     'field_specifier attribute')
            elif field_specifier != self.field_specifier:
                self._field_specifier = field_specifier
                # The keyword need also be updated
                keyword = self._keyword.split('.', 1)[0]
                self._keyword = '.'.join([keyword, field_specifier])
                self._modified = True

        @field_specifier.deleter
        def field_specifier(self):
            raise AttributeError('The field_specifier attribute may not be '
                                 'deleted from record-valued keyword cards.')

        @property
        def image(self):
            """
            The card "image", that is, the 80 byte character string that represents
            this card in an actual FITS header.
            """

            if self._image and not self._verified:
                self.verify('fix')
            if self._image is None or self._modified:
                self._image = self._format_image()
            return self._image

        @property
        def is_blank(self):
            """
            `True` if the card is completely blank--that is, it has no keyword,
            value, or comment.  It appears in the header as 80 spaces.

            Returns `False` otherwise.
            """

            if not self._verified:
                # The card image has not been parsed yet; compare directly with the
                # string representation of a blank card
                return self._image == BLANK_CARD

            # If the keyword, value, and comment are all empty (for self.value
            # explicitly check that it is a string value, since a blank value is
            # returned as '')
            return (not self.keyword and
                    (isinstance(self.value, string_types) and not self.value) and
                    not self.comment)

        @property
        @deprecated('0.1', alternative='the `.image` attribute')
        def cardimage(self):
            return self.image

        @deprecated('0.1', alternative='the `.image` attribute')
        def ascardimage(self, option='silentfix'):
            if not self._verified:
                self.verify(option)
            return self.image

        @classmethod
        def fromstring(cls, image):
            """
            Construct a `Card` object from a (raw) string. It will pad the string
            if it is not the length of a card image (80 columns).  If the card
            image is longer than 80 columns, assume it contains ``CONTINUE``
            card(s).
            """

            card = cls()
            card._image = _pad(image)
            card._verified = False
            return card

        @classmethod
        def normalize_keyword(cls, keyword):
            """
            `classmethod` to convert a keyword value that may contain a
            field-specifier to uppercase.  The effect is to raise the key to
            uppercase and leave the field specifier in its original case.

            Parameters
            ----------
            key : or str
                A keyword value or a ``keyword.field-specifier`` value
            """

            # Test first for the most common case: a standard FITS keyword provided
            # in standard all-caps
            if (len(keyword) <= KEYWORD_LENGTH and
                    cls._keywd_FSC_RE.match(keyword)):
                return keyword

            # Test if this is a record-valued keyword
            match = cls._rvkc_keyword_name_RE.match(keyword)

            if match:
                return '.'.join((match.group('keyword').strip().upper(),
                                 match.group('field_specifier')))
            elif len(keyword) > 9 and keyword[:9].upper() == 'HIERARCH ':
                # Remove 'HIERARCH' from HIERARCH keywords; this could lead to
                # ambiguity if there is actually a keyword card containing
                # "HIERARCH HIERARCH", but shame on you if you do that.
                return keyword[9:].strip()
            else:
                # A normal FITS keyword, but provided in non-standard case
                return keyword.strip().upper()

        def _check_if_rvkc(self, *args):
            """
            Determine whether or not the card is a record-valued keyword card.

            If one argument is given, that argument is treated as a full card image
            and parsed as such.  If two arguments are given, the first is treated
            as the card keyword (including the field-specifier if the card is
            intended as a RVKC), and the second as the card value OR the first value
            can be the base keyword, and the second value the 'field-specifier:
            value' string.

            If the check passes the ._keyword, ._value, and .field_specifier
            keywords are set.

            Examples
            --------

            ::

                self._check_if_rvkc('DP1', 'AXIS.1: 2')
                self._check_if_rvkc('DP1.AXIS.1', 2)
                self._check_if_rvkc('DP1     = AXIS.1: 2')
            """

            if not conf.enable_record_valued_keyword_cards:
                return False

            if len(args) == 1:
                self._check_if_rvkc_image(*args)
            elif len(args) == 2:
                keyword, value = args
                if not isinstance(keyword, string_types):
                    return False
                if keyword in self._commentary_keywords:
                    return False
                match = self._rvkc_keyword_name_RE.match(keyword)
                if match and isinstance(value, (int, float)):
                    self._init_rvkc(match.group('keyword'),
                                    match.group('field_specifier'), None, value)
                    return True

                # Testing for ': ' is a quick way to avoid running the full regular
                # expression, speeding this up for the majority of cases
                if isinstance(value, string_types) and value.find(': ') > 0:
                    match = self._rvkc_field_specifier_val_RE.match(value)
                    if match and self._keywd_FSC_RE.match(keyword):
                        self._init_rvkc(keyword, match.group('keyword'), value,
                                        match.group('val'))
                        return True

        def _check_if_rvkc_image(self, *args):
            """
            Implements `Card._check_if_rvkc` for the case of an unparsed card
            image.  If given one argument this is the full intact image.  If given
            two arguments the card has already been split between keyword and
            value+comment at the standard value indicator '= '.
            """

            if len(args) == 1:
                image = args[0]
                eq_idx = image.find(VALUE_INDICATOR)
                if eq_idx < 0 or eq_idx > 9:
                    return False
                keyword = image[:eq_idx]
                rest = image[eq_idx + len(VALUE_INDICATOR):]
            else:
                keyword, rest = args

            rest = rest.lstrip()

            # This test allows us to skip running the full regular expression for
            # the majority of cards that do not contain strings or that definitely
            # do not contain RVKC field-specifiers; it's very much a
            # micro-optimization but it does make a measurable difference
            if not rest or rest[0] != "'" or rest.find(': ') < 2:
                return False

            match = self._rvkc_keyword_val_comm_RE.match(rest)
            if match:
                self._init_rvkc(keyword, match.group('keyword'),
                                match.group('rawval'), match.group('val'))
                return True

        def _init_rvkc(self, keyword, field_specifier, field, value):
            """
            Sort of addendum to Card.__init__ to set the appropriate internal
            attributes if the card was determined to be a RVKC.
            """

            keyword_upper = keyword.upper()
            self._keyword = '.'.join((keyword_upper, field_specifier))
            self._rawkeyword = keyword_upper
            self._field_specifier = field_specifier
            self._value = _int_or_float(value)
            self._rawvalue = field

        def _parse_keyword(self):
            keyword = self._image[:KEYWORD_LENGTH].strip()
            keyword_upper = keyword.upper()
            val_ind_idx = self._image.find(VALUE_INDICATOR)

            special = self._commentary_keywords

            if (0 <= val_ind_idx <= KEYWORD_LENGTH or keyword_upper in special or
                    keyword_upper == 'CONTINUE'):
                # The value indicator should appear in byte 8, but we are flexible
                # and allow this to be fixed
                if val_ind_idx >= 0:
                    keyword = keyword[:val_ind_idx]
                    rest = self._image[val_ind_idx + len(VALUE_INDICATOR):]

                    # So far this looks like a standard FITS keyword; check whether
                    # the value represents a RVKC; if so then we pass things off to
                    # the RVKC parser
                    if self._check_if_rvkc_image(keyword, rest):
                        return self._keyword

                    keyword_upper = keyword_upper[:val_ind_idx]

                return keyword_upper
            elif (keyword_upper == 'HIERARCH' and self._image[8] == ' ' and
                  HIERARCH_VALUE_INDICATOR in self._image):
                # This is valid HIERARCH card as described by the HIERARCH keyword
                # convention:
                # http://fits.gsfc.nasa.gov/registry/hierarch_keyword.html
                self._hierarch = True
                self._value_indicator = HIERARCH_VALUE_INDICATOR
                keyword = self._image.split(HIERARCH_VALUE_INDICATOR, 1)[0][9:]
                return keyword.strip()
            else:
                warnings.warn('The following header keyword is invalid or follows '
                              'an unrecognized non-standard convention:\n%s' %
                              self._image, AstropyUserWarning)
                self._invalid = True
                return keyword

        def _parse_value(self):
            """Extract the keyword value from the card image."""

            # for commentary cards, no need to parse further
            # Likewise for invalid cards
            if self.keyword.upper() in self._commentary_keywords or self._invalid:
                return self._image[KEYWORD_LENGTH:].rstrip()

            if self._check_if_rvkc(self._image):
                return self._value

            if len(self._image) > self.length:
                values = []
                for card in self._itersubcards():
                    value = card.value.rstrip().replace("''", "'")
                    if value and value[-1] == '&':
                        value = value[:-1]
                    values.append(value)

                value = ''.join(values)

                self._valuestring = value
                return value

            m = self._value_NFSC_RE.match(self._split()[1])

            if m is None:
                raise VerifyError("Unparsable card (%s), fix it first with "
                                  ".verify('fix')." % self.keyword)

            if m.group('bool') is not None:
                value = m.group('bool') == 'T'
            elif m.group('strg') is not None:
                value = re.sub("''", "'", m.group('strg'))
            elif m.group('numr') is not None:
                #  Check for numbers with leading 0s.
                numr = self._number_NFSC_RE.match(m.group('numr'))
                digt = translate(numr.group('digt'), FIX_FP_TABLE2, ' ')
                if numr.group('sign') is None:
                    sign = ''
                else:
                    sign = numr.group('sign')
                value = _str_to_num(sign + digt)

            elif m.group('cplx') is not None:
                #  Check for numbers with leading 0s.
                real = self._number_NFSC_RE.match(m.group('real'))
                rdigt = translate(real.group('digt'), FIX_FP_TABLE2, ' ')
                if real.group('sign') is None:
                    rsign = ''
                else:
                    rsign = real.group('sign')
                value = _str_to_num(rsign + rdigt)
                imag = self._number_NFSC_RE.match(m.group('imag'))
                idigt = translate(imag.group('digt'), FIX_FP_TABLE2, ' ')
                if imag.group('sign') is None:
                    isign = ''
                else:
                    isign = imag.group('sign')
                value += _str_to_num(isign + idigt) * 1j
            else:
                value = UNDEFINED

            if not self._valuestring:
                self._valuestring = m.group('valu')
            return value

        def _parse_comment(self):
            """Extract the keyword value from the card image."""

            # for commentary cards, no need to parse further
            # likewise for invalid/unparseable cards
            if self.keyword in Card._commentary_keywords or self._invalid:
                return ''

            if len(self._image) > self.length:
                comments = []
                for card in self._itersubcards():
                    if card.comment:
                        comments.append(card.comment)
                comment = '/ ' + ' '.join(comments).rstrip()
                m = self._value_NFSC_RE.match(comment)
            else:
                m = self._value_NFSC_RE.match(self._split()[1])

            if m is not None:
                comment = m.group('comm')
                if comment:
                    return comment.rstrip()
            return ''

        def _split(self):
            """
            Split the card image between the keyword and the rest of the card.
            """

            if self._image is not None:
                # If we already have a card image, don't try to rebuild a new card
                # image, which self.image would do
                image = self._image
            else:
                image = self.image

            if self.keyword in self._commentary_keywords.union(['CONTINUE']):
                keyword, valuecomment = image.split(' ', 1)
            else:
                try:
                    delim_index = image.index(self._value_indicator)
                except ValueError:
                    delim_index = None

                # The equal sign may not be any higher than column 10; anything
                # past that must be considered part of the card value
                if delim_index is None:
                    keyword = image[:KEYWORD_LENGTH]
                    valuecomment = image[KEYWORD_LENGTH:]
                elif delim_index > 10 and image[:9] != 'HIERARCH ':
                    keyword = image[:8]
                    valuecomment = image[8:]
                else:
                    keyword, valuecomment = image.split(self._value_indicator, 1)
            return keyword.strip(), valuecomment.strip()

        def _fix_keyword(self):
            if self.field_specifier:
                keyword, field_specifier = self._keyword.split('.', 1)
                self._keyword = '.'.join([keyword.upper(), field_specifier])
            else:
                self._keyword = self._keyword.upper()
            self._modified = True

        def _fix_value(self):
            """Fix the card image for fixable non-standard compliance."""

            value = None
            keyword, valuecomment = self._split()
            m = self._value_NFSC_RE.match(valuecomment)

            # for the unparsable case
            if m is None:
                try:
                    value, comment = valuecomment.split('/', 1)
                    self.value = value.strip()
                    self.comment = comment.strip()
                except (ValueError, IndexError):
                    self.value = valuecomment
                self._valuestring = self._value
                return
            elif m.group('numr') is not None:
                numr = self._number_NFSC_RE.match(m.group('numr'))
                value = translate(numr.group('digt'), FIX_FP_TABLE, ' ')
                if numr.group('sign') is not None:
                    value = numr.group('sign') + value

            elif m.group('cplx') is not None:
                real = self._number_NFSC_RE.match(m.group('real'))
                rdigt = translate(real.group('digt'), FIX_FP_TABLE, ' ')
                if real.group('sign') is not None:
                    rdigt = real.group('sign') + rdigt

                imag = self._number_NFSC_RE.match(m.group('imag'))
                idigt = translate(imag.group('digt'), FIX_FP_TABLE, ' ')
                if imag.group('sign') is not None:
                    idigt = imag.group('sign') + idigt
                value = '(%s, %s)' % (rdigt, idigt)
            self._valuestring = value
            # The value itself has not been modified, but its serialized
            # representation (as stored in self._valuestring) has been changed, so
            # still set this card as having been modified (see ticket #137)
            self._modified = True

        def _format_keyword(self):
            if self.keyword:
                if self.field_specifier:
                    return '%-*s' % (KEYWORD_LENGTH, self.keyword.split('.', 1)[0])
                elif self._hierarch:
                    return 'HIERARCH %s ' % self.keyword
                else:
                    return '%-*s' % (KEYWORD_LENGTH, self.keyword)
            else:
                return ' ' * KEYWORD_LENGTH

        def _format_value(self):
            # value string
            float_types = (float, np.floating, complex, np.complexfloating)

            # Force the value to be parsed out first
            value = self.value
            # But work with the underlying raw value instead (to preserve
            # whitespace, for now...)
            value = self._value

            if self.keyword in self._commentary_keywords:
                # The value of a commentary card must be just a raw unprocessed
                # string
                value = str(value)
            elif (self._valuestring and not self._valuemodified and
                  isinstance(self.value, float_types)):
                # Keep the existing formatting for float/complex numbers
                value = '%20s' % self._valuestring
            elif self.field_specifier:
                value = _format_value(self._value).strip()
                value = "'%s: %s'" % (self.field_specifier, value)
            else:
                value = _format_value(value)

            # For HIERARCH cards the value should be shortened to conserve space
            if not self.field_specifier and len(self.keyword) > KEYWORD_LENGTH:
                value = value.strip()

            return value

        def _format_comment(self):
            if not self.comment:
                return ''
            else:
                return ' / %s' % self._comment

        def _format_image(self):
            keyword = self._format_keyword()

            value = self._format_value()
            is_commentary = keyword.strip() in self._commentary_keywords
            if is_commentary:
                comment = ''
            else:
                comment = self._format_comment()

            # equal sign string
            # by default use the standard value indicator even for HIERARCH cards;
            # later we may abbreviate it if necessary
            delimiter = VALUE_INDICATOR
            if is_commentary:
                delimiter = ''

            # put all parts together
            output = ''.join([keyword, delimiter, value, comment])

            # For HIERARCH cards we can save a bit of space if necessary by
            # removing the space between the keyword and the equals sign; I'm
            # guessing this is part of the HIEARCH card specification
            keywordvalue_length = len(keyword) + len(delimiter) + len(value)
            if (keywordvalue_length > self.length and
                    keyword.startswith('HIERARCH')):
                if (keywordvalue_length == self.length + 1 and keyword[-1] == ' '):
                    output = ''.join([keyword[:-1], delimiter, value, comment])
                else:
                    # I guess the HIERARCH card spec is incompatible with CONTINUE
                    # cards
                    raise ValueError('The keyword %s with its value is too long' %
                                     self.keyword)

            if len(output) <= self.length:
                output = '%-80s' % output
            else:
                # longstring case (CONTINUE card)
                # try not to use CONTINUE if the string value can fit in one line.
                # Instead, just truncate the comment
                if (isinstance(self.value, string_types) and
                    len(value) > (self.length - 10)):
                    output = self._format_long_image()
                else:
                    warnings.warn('Card is too long, comment will be truncated.',
                                  VerifyWarning)
                    output = output[:Card.length]
            return output

        def _format_long_image(self):
            """
            Break up long string value/comment into ``CONTINUE`` cards.
            This is a primitive implementation: it will put the value
            string in one block and the comment string in another.  Also,
            it does not break at the blank space between words.  So it may
            not look pretty.
            """

            if self.keyword in Card._commentary_keywords:
                return self._format_long_commentary_image()

            value_length = 67
            comment_length = 64
            output = []

            # do the value string
            value = self._value.replace("'", "''")
            words = _words_group(value, value_length)
            for idx, word in enumerate(words):
                if idx == 0:
                    headstr = '%-*s= ' % (KEYWORD_LENGTH, self.keyword)
                else:
                    headstr = 'CONTINUE  '

                # If this is the final CONTINUE remove the '&'
                if not self.comment and idx == len(words) - 1:
                    value_format = "'%-s'"
                else:
                    value_format = "'%-s&'"

                value = value_format % word

                output.append('%-80s' % (headstr + value))

            # do the comment string
            comment_format = "%-s"
            if self.comment:
                words = _words_group(self.comment, comment_length)
                for idx, word in enumerate(words):
                    # If this is the final CONTINUE remove the '&'
                    if idx == len(words) - 1:
                        headstr = "CONTINUE  '' / "
                    else:
                        headstr = "CONTINUE  '&' / "

                    comment = headstr + comment_format % word
                    output.append('%-80s' % comment)

            return ''.join(output)

        def _format_long_commentary_image(self):
            """
            If a commentary card's value is too long to fit on a single card, this
            will render the card as multiple consecutive commentary card of the
            same type.
            """

            maxlen = Card.length - KEYWORD_LENGTH
            value = self._format_value()
            output = []
            idx = 0
            while idx < len(value):
                output.append(str(Card(self.keyword, value[idx:idx + maxlen])))
                idx += maxlen
            return ''.join(output)

        def _verify(self, option='warn'):
            self._verified = True

            errs = _ErrList([])
            fix_text = 'Fixed %r card to meet the FITS standard.' % self.keyword

            # Don't try to verify cards that already don't meet any recognizable
            # standard
            if self._invalid:
                return errs

            # verify the equal sign position
            if (self.keyword not in self._commentary_keywords and
                (self._image and self._image[:9].upper() != 'HIERARCH ' and
                 self._image.find('=') != 8)):
                errs.append(self.run_option(
                    option,
                    err_text='Card %r is not FITS standard (equal sign not '
                             'at column 8).' % self.keyword,
                    fix_text=fix_text,
                    fix=self._fix_value))

            # verify the key, it is never fixable
            # always fix silently the case where "=" is before column 9,
            # since there is no way to communicate back to the _keys.
            if ((self._image and self._image[:8].upper() == 'HIERARCH') or
                    self._hierarch):
                pass
            else:
                if self._image:
                    # PyFITS will auto-uppercase any standard keyword, so lowercase
                    # keywords can only occur if they came from the wild
                    keyword = self._split()[0]
                    if keyword != keyword.upper():
                        # Keyword should be uppercase unless it's a HIERARCH card
                        errs.append(self.run_option(
                            option,
                            err_text='Card keyword %r is not upper case.' %
                                      keyword,
                            fix_text=fix_text,
                            fix=self._fix_keyword))

                keyword = self.keyword
                if self.field_specifier:
                    keyword = keyword.split('.', 1)[0]

                if not self._keywd_FSC_RE.match(keyword):
                    errs.append(self.run_option(
                        option,
                        err_text='Illegal keyword name %s' % repr(keyword),
                        fixable=False))

            # verify the value, it may be fixable
            keyword, valuecomment = self._split()
            if self.keyword in self._commentary_keywords:
                # For commentary keywords all that needs to be ensured is that it
                # contains only printable ASCII characters
                if not self._ascii_text_re.match(valuecomment):
                    errs.append(self.run_option(
                        option,
                        err_text='Unprintable string %r; commentary cards may '
                                 'only contain printable ASCII characters' %
                                 valuecomment,
                        fixable=False))
            else:
                m = self._value_FSC_RE.match(valuecomment)
                if not m:
                    errs.append(self.run_option(
                        option,
                        err_text='Card %r is not FITS standard (invalid value '
                                 'string: %r).' % (self.keyword, valuecomment),
                        fix_text=fix_text,
                        fix=self._fix_value))

            # verify the comment (string), it is never fixable
            m = self._value_NFSC_RE.match(valuecomment)
            if m is not None:
                comment = m.group('comm')
                if comment is not None:
                    if not self._ascii_text_re.match(comment):
                        errs.append(self.run_option(
                            option,
                            err_text='Unprintable string %r; header comments may '
                                     'only contain printable ASCII characters' %
                                     comment,
                            fixable=False))

            return errs

        def _itersubcards(self):
            """
            If the card image is greater than 80 characters, it should consist of a
            normal card followed by one or more CONTINUE card.  This method returns
            the subcards that make up this logical card.
            """

            ncards = len(self._image) // Card.length

            for idx in range(0, Card.length * ncards, Card.length):
                card = Card.fromstring(self._image[idx:idx + Card.length])
                if idx > 0 and card.keyword.upper() != 'CONTINUE':
                    raise VerifyError(
                            'Long card images must have CONTINUE cards after '
                            'the first card.')

                if not isinstance(card.value, str):
                    raise VerifyError('CONTINUE cards must have string values.')

                yield card

    def create_card(key='', value='', comment=''):
        return Card(key, value, comment)
    create_card.__doc__ = Card.__init__.__doc__
    # For API backwards-compatibility
    create_card = deprecated('0.1', name='create_card',
                             alternative='``Card.__init__``',
                             pending=False)(create_card)

    def create_card_from_string(input):
        return Card.fromstring(input)
    create_card_from_string.__doc__ = Card.fromstring.__doc__
    # For API backwards-compat
    create_card_from_string = deprecated('0.1', name='create_card_from_string',
                                         alternative=':meth:`Card.fromstring`',
                                         pending=False)(create_card_from_string)

    def upper_key(key):
        return Card.normalize_keyword(key)
    upper_key.__doc__ = Card.normalize_keyword.__doc__
    # For API backwards-compat
    upper_key = deprecated('0.1', name='upper_key',
                           alternative=':meth:`Card.normalize_keyword`',
                           pending=False)(upper_key)

    def _int_or_float(s):
        """
        Converts an a string to an int if possible, or to a float.

        If the string is neither a string or a float a value error is raised.
        """

        if isinstance(s, float):
            # Already a float so just pass through
            return s

        try:
            return int(s)
        except (ValueError, TypeError):
            try:
                return float(s)
            except (ValueError, TypeError) as e:
                raise ValueError(str(e))

    def _format_value(value):
        """
        Converts a card value to its appropriate string representation as
        defined by the FITS format.
        """

        # string value should occupies at least 8 columns, unless it is
        # a null string
        if isinstance(value, string_types):
            if value == '':
                return "''"
            else:
                exp_val_str = value.replace("'", "''")
                val_str = "'%-8s'" % exp_val_str
                return '%-20s' % val_str

        # must be before int checking since bool is also int
        elif isinstance(value, (bool, np.bool_)):
            return '%20s' % repr(value)[0]  # T or F

        elif _is_int(value):
            return '%20d' % value

        elif isinstance(value, (float, np.floating)):
            return '%20s' % _format_float(value)

        elif isinstance(value, (complex, np.complexfloating)):
            val_str = '(%s, %s)' % (_format_float(value.real),
                                    _format_float(value.imag))
            return '%20s' % val_str

        elif isinstance(value, Undefined):
            return ''
        else:
            return ''

    def _format_float(value):
        """Format a floating number to make sure it gets the decimal point."""

        value_str = '%.16G' % value
        if '.' not in value_str and 'E' not in value_str:
            value_str += '.0'
        elif 'E' in value_str:
            # On some Windows builds of Python (and possibly other platforms?) the
            # exponent is zero-padded out to, it seems, three digits.  Normalize
            # the format to pad only to two digits.
            significand, exponent = value_str.split('E')
            if exponent[0] in ('+', '-'):
                sign = exponent[0]
                exponent = exponent[1:]
            else:
                sign = ''
            value_str = '%sE%s%02d' % (significand, sign, int(exponent))

        # Limit the value string to at most 20 characters.
        str_len = len(value_str)

        if str_len > 20:
            idx = value_str.find('E')

            if idx < 0:
                value_str = value_str[:20]
            else:
                value_str = value_str[:20 - (str_len - idx)] + value_str[idx:]

        return value_str

    def _pad(input):
        """Pad blank space to the input string to be multiple of 80."""

        _len = len(input)
        if _len == Card.length:
            return input
        elif _len > Card.length:
            strlen = _len % Card.length
            if strlen == 0:
                return input
            else:
                return input + ' ' * (Card.length - strlen)

        # minimum length is 80
        else:
            strlen = _len % Card.length
            return input + ' ' * (Card.length - strlen)