# Django 2.2.9.dev20191202104323 文档

# django.utils.text 源代码

    import html.entities
    import re
    import unicodedata
    from gzip import GzipFile
    from io import BytesIO

    from django.utils.functional import SimpleLazyObject, keep_lazy_text, lazy
    from django.utils.translation import gettext as _, gettext_lazy, pgettext

    @keep_lazy_text
    def capfirst(x):
        """Capitalize the first letter of a string."""
        return x and str(x)[0].upper() + str(x)[1:]

    # Set up regular expressions
    re_words = re.compile(r'<[^>]+?>|([^<>\s]+)', re.S)
    re_chars = re.compile(r'<[^>]+?>|(.)', re.S)
    re_tag = re.compile(r'<(/)?(\S+?)(?:(\s*/)|\s.*?)?>', re.S)
    re_newlines = re.compile(r'\r\n|\r')  # Used in normalize_newlines
    re_camel_case = re.compile(r'(((?<=[a-z])[A-Z])|([A-Z](?![A-Z]|$)))')

    @keep_lazy_text
    def wrap(text, width):
        """
        A word-wrap function that preserves existing line breaks. Expects that
        existing line breaks are posix newlines.

        Preserve all white space except added line breaks consume the space on
        which they break the line.

        Don't wrap long words, thus the output text may have lines longer than
        ``width``.
        """
        def _generator():
            for line in text.splitlines(True):  # True keeps trailing linebreaks
                max_width = min((line.endswith('\n') and width + 1 or width), width)
                while len(line) > max_width:
                    space = line[:max_width + 1].rfind(' ') + 1
                    if space == 0:
                        space = line.find(' ') + 1
                        if space == 0:
                            yield line
                            line = ''
                            break
                    yield '%s\n' % line[:space - 1]
                    line = line[space:]
                    max_width = min((line.endswith('\n') and width + 1 or width), width)
                if line:
                    yield line
        return ''.join(_generator())

    class Truncator(SimpleLazyObject):
        """
        An object used to truncate text, either by characters or words.
        """
        def __init__(self, text):
            super().__init__(lambda: str(text))

        def add_truncation_text(self, text, truncate=None):
            if truncate is None:
                truncate = pgettext(
                    'String to return when truncating text',
                    '%(truncated_text)s…')
            if '%(truncated_text)s' in truncate:
                return truncate % {'truncated_text': text}
            # The truncation text didn't contain the %(truncated_text)s string
            # replacement argument so just append it to the text.
            if text.endswith(truncate):
                # But don't append the truncation text if the current text already
                # ends in this.
                return text
            return '%s%s' % (text, truncate)

        def chars(self, num, truncate=None, html=False):
            """
            Return the text truncated to be no longer than the specified number
            of characters.

            `truncate` specifies what should be used to notify that the string has
            been truncated, defaulting to a translatable string of an ellipsis.
            """
            self._setup()
            length = int(num)
            text = unicodedata.normalize('NFC', self._wrapped)

            # Calculate the length to truncate to (max length - end_text length)
            truncate_len = length
            for char in self.add_truncation_text('', truncate):
                if not unicodedata.combining(char):
                    truncate_len -= 1
                    if truncate_len == 0:
                        break
            if html:
                return self._truncate_html(length, truncate, text, truncate_len, False)
            return self._text_chars(length, truncate, text, truncate_len)

        def _text_chars(self, length, truncate, text, truncate_len):
            """Truncate a string after a certain number of chars."""
            s_len = 0
            end_index = None
            for i, char in enumerate(text):
                if unicodedata.combining(char):
                    # Don't consider combining characters
                    # as adding to the string length
                    continue
                s_len += 1
                if end_index is None and s_len > truncate_len:
                    end_index = i
                if s_len > length:
                    # Return the truncated string
                    return self.add_truncation_text(text[:end_index or 0],
                                                    truncate)

            # Return the original string since no truncation was necessary
            return text

        def words(self, num, truncate=None, html=False):
            """
            Truncate a string after a certain number of words. `truncate` specifies
            what should be used to notify that the string has been truncated,
            defaulting to ellipsis.
            """
            self._setup()
            length = int(num)
            if html:
                return self._truncate_html(length, truncate, self._wrapped, length, True)
            return self._text_words(length, truncate)

        def _text_words(self, length, truncate):
            """
            Truncate a string after a certain number of words.

            Strip newlines in the string.
            """
            words = self._wrapped.split()
            if len(words) > length:
                words = words[:length]
                return self.add_truncation_text(' '.join(words), truncate)
            return ' '.join(words)

        def _truncate_html(self, length, truncate, text, truncate_len, words):
            """
            Truncate HTML to a certain number of chars (not counting tags and
            comments), or, if words is True, then to a certain number of words.
            Close opened tags if they were correctly closed in the given HTML.

            Preserve newlines in the HTML.
            """
            if words and length <= 0:
                return ''

            html4_singlets = (
                'br', 'col', 'link', 'base', 'img',
                'param', 'area', 'hr', 'input'
            )

            # Count non-HTML chars/words and keep note of open tags
            pos = 0
            end_text_pos = 0
            current_len = 0
            open_tags = []

            regex = re_words if words else re_chars

            while current_len <= length:
                m = regex.search(text, pos)
                if not m:
                    # Checked through whole string
                    break
                pos = m.end(0)
                if m.group(1):
                    # It's an actual non-HTML word or char
                    current_len += 1
                    if current_len == truncate_len:
                        end_text_pos = pos
                    continue
                # Check for tag
                tag = re_tag.match(m.group(0))
                if not tag or current_len >= truncate_len:
                    # Don't worry about non tags or tags after our truncate point
                    continue
                closing_tag, tagname, self_closing = tag.groups()
                # Element names are always case-insensitive
                tagname = tagname.lower()
                if self_closing or tagname in html4_singlets:
                    pass
                elif closing_tag:
                    # Check for match in open tags list
                    try:
                        i = open_tags.index(tagname)
                    except ValueError:
                        pass
                    else:
                        # SGML: An end tag closes, back to the matching start tag,
                        # all unclosed intervening start tags with omitted end tags
                        open_tags = open_tags[i + 1:]
                else:
                    # Add it to the start of the open tags list
                    open_tags.insert(0, tagname)

            if current_len <= length:
                return text
            out = text[:end_text_pos]
            truncate_text = self.add_truncation_text('', truncate)
            if truncate_text:
                out += truncate_text
            # Close any tags still open
            for tag in open_tags:
                out += '</%s>' % tag
            # Return string
            return out

    @keep_lazy_text
    def get_valid_filename(s):
        """
        Return the given string converted to a string that can be used for a clean
        filename. Remove leading and trailing spaces; convert other spaces to
        underscores; and remove anything that is not an alphanumeric, dash,
        underscore, or dot.
        >>> get_valid_filename("john's portrait in 2004.jpg")
        'johns_portrait_in_2004.jpg'
        """
        s = str(s).strip().replace(' ', '_')
        return re.sub(r'(?u)[^-\w.]', '', s)

    @keep_lazy_text
    def get_text_list(list_, last_word=gettext_lazy('or')):
        """
        >>> get_text_list(['a', 'b', 'c', 'd'])
        'a, b, c or d'
        >>> get_text_list(['a', 'b', 'c'], 'and')
        'a, b and c'
        >>> get_text_list(['a', 'b'], 'and')
        'a and b'
        >>> get_text_list(['a'])
        'a'
        >>> get_text_list([])
        ''
        """
        if not list_:
            return ''
        if len(list_) == 1:
            return str(list_[0])
        return '%s %s %s' % (
            # Translators: This string is used as a separator between list elements
            _(', ').join(str(i) for i in list_[:-1]), str(last_word), str(list_[-1])
        )

    @keep_lazy_text
    def normalize_newlines(text):
        """Normalize CRLF and CR newlines to just LF."""
        return re_newlines.sub('\n', str(text))

    @keep_lazy_text
    def phone2numeric(phone):
        """Convert a phone number with letters into its numeric equivalent."""
        char2number = {
            'a': '2', 'b': '2', 'c': '2', 'd': '3', 'e': '3', 'f': '3', 'g': '4',
            'h': '4', 'i': '4', 'j': '5', 'k': '5', 'l': '5', 'm': '6', 'n': '6',
            'o': '6', 'p': '7', 'q': '7', 'r': '7', 's': '7', 't': '8', 'u': '8',
            'v': '8', 'w': '9', 'x': '9', 'y': '9', 'z': '9',
        }
        return ''.join(char2number.get(c, c) for c in phone.lower())

    # From http://www.xhaus.com/alan/python/httpcomp.html#gzip
    # Used with permission.
    def compress_string(s):
        zbuf = BytesIO()
        with GzipFile(mode='wb', compresslevel=6, fileobj=zbuf, mtime=0) as zfile:
            zfile.write(s)
        return zbuf.getvalue()

    class StreamingBuffer(BytesIO):
        def read(self):
            ret = self.getvalue()
            self.seek(0)
            self.truncate()
            return ret

    # Like compress_string, but for iterators of strings.
    def compress_sequence(sequence):
        buf = StreamingBuffer()
        with GzipFile(mode='wb', compresslevel=6, fileobj=buf, mtime=0) as zfile:
            # Output headers...
            yield buf.read()
            for item in sequence:
                zfile.write(item)
                data = buf.read()
                if data:
                    yield data
        yield buf.read()

    # Expression to match some_token and some_token="with spaces" (and similarly
    # for single-quoted strings).
    smart_split_re = re.compile(r"""
        ((?:
            [^\s'"]*
            (?:
                (?:"(?:[^"\\]|\\.)*" | '(?:[^'\\]|\\.)*')
                [^\s'"]*
            )+
        ) | \S+)
    """, re.VERBOSE)

    def smart_split(text):
        r"""
        Generator that splits a string by spaces, leaving quoted phrases together.
        Supports both single and double quotes, and supports escaping quotes with
        backslashes. In the output, strings will keep their initial and trailing
        quote marks and escaped quotes will remain escaped (the results can then
        be further processed with unescape_string_literal()).

        >>> list(smart_split(r'This is "a person\'s" test.'))
        ['This', 'is', '"a person\\\'s"', 'test.']
        >>> list(smart_split(r"Another 'person\'s' test."))
        ['Another', "'person\\'s'", 'test.']
        >>> list(smart_split(r'A "\"funky\" style" test.'))
        ['A', '"\\"funky\\" style"', 'test.']
        """
        for bit in smart_split_re.finditer(str(text)):
            yield bit.group(0)

    def _replace_entity(match):
        text = match.group(1)
        if text[0] == '#':
            text = text[1:]
            try:
                if text[0] in 'xX':
                    c = int(text[1:], 16)
                else:
                    c = int(text)
                return chr(c)
            except ValueError:
                return match.group(0)
        else:
            try:
                return chr(html.entities.name2codepoint[text])
            except (ValueError, KeyError):
                return match.group(0)

    _entity_re = re.compile(r"&(#?[xX]?(?:[0-9a-fA-F]+|\w{1,8}));")

    @keep_lazy_text
    def unescape_entities(text):
        return _entity_re.sub(_replace_entity, str(text))

    @keep_lazy_text
    def unescape_string_literal(s):
        r"""
        Convert quoted string literals to unquoted strings with escaped quotes and
        backslashes unquoted::

            >>> unescape_string_literal('"abc"')
            'abc'
            >>> unescape_string_literal("'abc'")
            'abc'
            >>> unescape_string_literal('"a \"bc\""')
            'a "bc"'
            >>> unescape_string_literal("'\'ab\' c'")
            "'ab' c"
        """
        if s[0] not in "\"'" or s[-1] != s[0]:
            raise ValueError("Not a string literal: %r" % s)
        quote = s[0]
        return s[1:-1].replace(r'\%s' % quote, quote).replace(r'\\', '\\')

    @keep_lazy_text
    def slugify(value, allow_unicode=False):
        """
        Convert to ASCII if 'allow_unicode' is False. Convert spaces to hyphens.
        Remove characters that aren't alphanumerics, underscores, or hyphens.
        Convert to lowercase. Also strip leading and trailing whitespace.
        """
        value = str(value)
        if allow_unicode:
            value = unicodedata.normalize('NFKC', value)
        else:
            value = unicodedata.normalize('NFKD', value).encode('ascii', 'ignore').decode('ascii')
        value = re.sub(r'[^\w\s-]', '', value).strip().lower()
        return re.sub(r'[-\s]+', '-', value)

    def camel_case_to_spaces(value):
        """
        Split CamelCase and convert to lowercase. Strip surrounding whitespace.
        """
        return re_camel_case.sub(r' \1', value).strip().lower()

    def _format_lazy(format_string, *args, **kwargs):
        """
        Apply str.format() on 'format_string' where format_string, args,
        and/or kwargs might be lazy.
        """
        return format_string.format(*args, **kwargs)

    format_lazy = lazy(_format_lazy, str)