# Source code for pathlib

    import fnmatch
    import functools
    import io
    import ntpath
    import os
    import posixpath
    import re
    import sys
    from _collections_abc import Sequence
    from errno import EINVAL, ENOENT, ENOTDIR, EBADF, ELOOP
    from operator import attrgetter
    from stat import S_ISDIR, S_ISLNK, S_ISREG, S_ISSOCK, S_ISBLK, S_ISCHR, S_ISFIFO
    from urllib.parse import quote_from_bytes as urlquote_from_bytes

    supports_symlinks = True
    if os.name == 'nt':
        import nt
        if sys.getwindowsversion()[:2] >= (6, 0):
            from nt import _getfinalpathname
        else:
            supports_symlinks = False
            _getfinalpathname = None
    else:
        nt = None

    __all__ = [
        "PurePath", "PurePosixPath", "PureWindowsPath",
        "Path", "PosixPath", "WindowsPath",
        ]

    #
    # Internals
    #

    # EBADF - guard against macOS `stat` throwing EBADF
    _IGNORED_ERROS = (ENOENT, ENOTDIR, EBADF, ELOOP)

    _IGNORED_WINERRORS = (
        21,  # ERROR_NOT_READY - drive exists but is not accessible
        1921,  # ERROR_CANT_RESOLVE_FILENAME - fix for broken symlink pointing to itself
    )

    def _ignore_error(exception):
        return (getattr(exception, 'errno', None) in _IGNORED_ERROS or
                getattr(exception, 'winerror', None) in _IGNORED_WINERRORS)

    def _is_wildcard_pattern(pat):
        # Whether this pattern needs actual matching using fnmatch, or can
        # be looked up directly as a file.
        return "*" in pat or "?" in pat or "[" in pat

    class _Flavour(object):
        """A flavour implements a particular (platform-specific) set of path
        semantics."""

        def __init__(self):
            self.join = self.sep.join

        def parse_parts(self, parts):
            parsed = []
            sep = self.sep
            altsep = self.altsep
            drv = root = ''
            it = reversed(parts)
            for part in it:
                if not part:
                    continue
                if altsep:
                    part = part.replace(altsep, sep)
                drv, root, rel = self.splitroot(part)
                if sep in rel:
                    for x in reversed(rel.split(sep)):
                        if x and x != '.':
                            parsed.append(sys.intern(x))
                else:
                    if rel and rel != '.':
                        parsed.append(sys.intern(rel))
                if drv or root:
                    if not drv:
                        # If no drive is present, try to find one in the previous
                        # parts. This makes the result of parsing e.g.
                        # ("C:", "/", "a") reasonably intuitive.
                        for part in it:
                            if not part:
                                continue
                            if altsep:
                                part = part.replace(altsep, sep)
                            drv = self.splitroot(part)[0]
                            if drv:
                                break
                    break
            if drv or root:
                parsed.append(drv + root)
            parsed.reverse()
            return drv, root, parsed

        def join_parsed_parts(self, drv, root, parts, drv2, root2, parts2):
            """
            Join the two paths represented by the respective
            (drive, root, parts) tuples.  Return a new (drive, root, parts) tuple.
            """
            if root2:
                if not drv2 and drv:
                    return drv, root2, [drv + root2] + parts2[1:]
            elif drv2:
                if drv2 == drv or self.casefold(drv2) == self.casefold(drv):
                    # Same drive => second path is relative to the first
                    return drv, root, parts + parts2[1:]
            else:
                # Second path is non-anchored (common case)
                return drv, root, parts + parts2
            return drv2, root2, parts2

    class _WindowsFlavour(_Flavour):
        # Reference for Windows paths can be found at
        # http://msdn.microsoft.com/en-us/library/aa365247%28v=vs.85%29.aspx

        sep = '\\'
        altsep = '/'
        has_drv = True
        pathmod = ntpath

        is_supported = (os.name == 'nt')

        drive_letters = set('abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ')
        ext_namespace_prefix = '\\\\?\\'

        reserved_names = (
            {'CON', 'PRN', 'AUX', 'NUL'} |
            {'COM%d' % i for i in range(1, 10)} |
            {'LPT%d' % i for i in range(1, 10)}
            )

        # Interesting findings about extended paths:
        # - '\\?\c:\a', '//?/c:\a' and '//?/c:/a' are all supported
        #   but '\\?\c:/a' is not
        # - extended paths are always absolute; "relative" extended paths will
        #   fail.

        def splitroot(self, part, sep=sep):
            first = part[0:1]
            second = part[1:2]
            if (second == sep and first == sep):
                # XXX extended paths should also disable the collapsing of "."
                # components (according to MSDN docs).
                prefix, part = self._split_extended_path(part)
                first = part[0:1]
                second = part[1:2]
            else:
                prefix = ''
            third = part[2:3]
            if (second == sep and first == sep and third != sep):
                # is a UNC path:
                # vvvvvvvvvvvvvvvvvvvvv root
                # \\machine\mountpoint\directory\etc\...
                #            directory ^^^^^^^^^^^^^^
                index = part.find(sep, 2)
                if index != -1:
                    index2 = part.find(sep, index + 1)
                    # a UNC path can't have two slashes in a row
                    # (after the initial two)
                    if index2 != index + 1:
                        if index2 == -1:
                            index2 = len(part)
                        if prefix:
                            return prefix + part[1:index2], sep, part[index2+1:]
                        else:
                            return part[:index2], sep, part[index2+1:]
            drv = root = ''
            if second == ':' and first in self.drive_letters:
                drv = part[:2]
                part = part[2:]
                first = third
            if first == sep:
                root = first
                part = part.lstrip(sep)
            return prefix + drv, root, part

        def casefold(self, s):
            return s.lower()

        def casefold_parts(self, parts):
            return [p.lower() for p in parts]

        def resolve(self, path, strict=False):
            s = str(path)
            if not s:
                return os.getcwd()
            previous_s = None
            if _getfinalpathname is not None:
                if strict:
                    return self._ext_to_normal(_getfinalpathname(s))
                else:
                    tail_parts = []  # End of the path after the first one not found
                    while True:
                        try:
                            s = self._ext_to_normal(_getfinalpathname(s))
                        except FileNotFoundError:
                            previous_s = s
                            s, tail = os.path.split(s)
                            tail_parts.append(tail)
                            if previous_s == s:
                                return path
                        else:
                            return os.path.join(s, *reversed(tail_parts))
            # Means fallback on absolute
            return None

        def _split_extended_path(self, s, ext_prefix=ext_namespace_prefix):
            prefix = ''
            if s.startswith(ext_prefix):
                prefix = s[:4]
                s = s[4:]
                if s.startswith('UNC\\'):
                    prefix += s[:3]
                    s = '\\' + s[3:]
            return prefix, s

        def _ext_to_normal(self, s):
            # Turn back an extended path into a normal DOS-like path
            return self._split_extended_path(s)[1]

        def is_reserved(self, parts):
            # NOTE: the rules for reserved names seem somewhat complicated
            # (e.g. r"..\NUL" is reserved but not r"foo\NUL").
            # We err on the side of caution and return True for paths which are
            # not considered reserved by Windows.
            if not parts:
                return False
            if parts[0].startswith('\\\\'):
                # UNC paths are never reserved
                return False
            return parts[-1].partition('.')[0].upper() in self.reserved_names

        def make_uri(self, path):
            # Under Windows, file URIs use the UTF-8 encoding.
            drive = path.drive
            if len(drive) == 2 and drive[1] == ':':
                # It's a path on a local drive => 'file:///c:/a/b'
                rest = path.as_posix()[2:].lstrip('/')
                return 'file:///%s/%s' % (
                    drive, urlquote_from_bytes(rest.encode('utf-8')))
            else:
                # It's a path on a network drive => 'file://host/share/a/b'
                return 'file:' + urlquote_from_bytes(path.as_posix().encode('utf-8'))

        def gethomedir(self, username):
            if 'HOME' in os.environ:
                userhome = os.environ['HOME']
            elif 'USERPROFILE' in os.environ:
                userhome = os.environ['USERPROFILE']
            elif 'HOMEPATH' in os.environ:
                try:
                    drv = os.environ['HOMEDRIVE']
                except KeyError:
                    drv = ''
                userhome = drv + os.environ['HOMEPATH']
            else:
                raise RuntimeError("Can't determine home directory")

            if username:
                # Try to guess user home directory.  By default all users
                # directories are located in the same place and are named by
                # corresponding usernames.  If current user home directory points
                # to nonstandard place, this guess is likely wrong.
                if os.environ['USERNAME'] != username:
                    drv, root, parts = self.parse_parts((userhome,))
                    if parts[-1] != os.environ['USERNAME']:
                        raise RuntimeError("Can't determine home directory "
                                           "for %r" % username)
                    parts[-1] = username
                    if drv or root:
                        userhome = drv + root + self.join(parts[1:])
                    else:
                        userhome = self.join(parts)
            return userhome

    class _PosixFlavour(_Flavour):
        sep = '/'
        altsep = ''
        has_drv = False
        pathmod = posixpath

        is_supported = (os.name != 'nt')

        def splitroot(self, part, sep=sep):
            if part and part[0] == sep:
                stripped_part = part.lstrip(sep)
                # According to POSIX path resolution:
                # http://pubs.opengroup.org/onlinepubs/009695399/basedefs/xbd_chap04.html#tag_04_11
                # "A pathname that begins with two successive slashes may be
                # interpreted in an implementation-defined manner, although more
                # than two leading slashes shall be treated as a single slash".
                if len(part) - len(stripped_part) == 2:
                    return '', sep * 2, stripped_part
                else:
                    return '', sep, stripped_part
            else:
                return '', '', part

        def casefold(self, s):
            return s

        def casefold_parts(self, parts):
            return parts

        def resolve(self, path, strict=False):
            sep = self.sep
            accessor = path._accessor
            seen = {}
            def _resolve(path, rest):
                if rest.startswith(sep):
                    path = ''

                for name in rest.split(sep):
                    if not name or name == '.':
                        # current dir
                        continue
                    if name == '..':
                        # parent dir
                        path, _, _ = path.rpartition(sep)
                        continue
                    newpath = path + sep + name
                    if newpath in seen:
                        # Already seen this path
                        path = seen[newpath]
                        if path is not None:
                            # use cached value
                            continue
                        # The symlink is not resolved, so we must have a symlink loop.
                        raise RuntimeError("Symlink loop from %r" % newpath)
                    # Resolve the symbolic link
                    try:
                        target = accessor.readlink(newpath)
                    except OSError as e:
                        if e.errno != EINVAL and strict:
                            raise
                        # Not a symlink, or non-strict mode. We just leave the path
                        # untouched.
                        path = newpath
                    else:
                        seen[newpath] = None # not resolved symlink
                        path = _resolve(path, target)
                        seen[newpath] = path # resolved symlink

                return path
            # NOTE: according to POSIX, getcwd() cannot contain path components
            # which are symlinks.
            base = '' if path.is_absolute() else os.getcwd()
            return _resolve(base, str(path)) or sep

        def is_reserved(self, parts):
            return False

        def make_uri(self, path):
            # We represent the path using the local filesystem encoding,
            # for portability to other applications.
            bpath = bytes(path)
            return 'file://' + urlquote_from_bytes(bpath)

        def gethomedir(self, username):
            if not username:
                try:
                    return os.environ['HOME']
                except KeyError:
                    import pwd
                    return pwd.getpwuid(os.getuid()).pw_dir
            else:
                import pwd
                try:
                    return pwd.getpwnam(username).pw_dir
                except KeyError:
                    raise RuntimeError("Can't determine home directory "
                                       "for %r" % username)

    _windows_flavour = _WindowsFlavour()
    _posix_flavour = _PosixFlavour()

    class _Accessor:
        """An accessor implements a particular (system-specific or not) way of
        accessing paths on the filesystem."""

    class _NormalAccessor(_Accessor):

        stat = os.stat

        lstat = os.lstat

        open = os.open

        listdir = os.listdir

        scandir = os.scandir

        chmod = os.chmod

        if hasattr(os, "lchmod"):
            lchmod = os.lchmod
        else:
            def lchmod(self, pathobj, mode):
                raise NotImplementedError("lchmod() not available on this system")

        mkdir = os.mkdir

        unlink = os.unlink

        rmdir = os.rmdir

        rename = os.rename

        replace = os.replace

        if nt:
            if supports_symlinks:
                symlink = os.symlink
            else:
                def symlink(a, b, target_is_directory):
                    raise NotImplementedError("symlink() not available on this system")
        else:
            # Under POSIX, os.symlink() takes two args
            @staticmethod
            def symlink(a, b, target_is_directory):
                return os.symlink(a, b)

        utime = os.utime

        # Helper for resolve()
        def readlink(self, path):
            return os.readlink(path)

    _normal_accessor = _NormalAccessor()

    #
    # Globbing helpers
    #

    def _make_selector(pattern_parts):
        pat = pattern_parts[0]
        child_parts = pattern_parts[1:]
        if pat == '**':
            cls = _RecursiveWildcardSelector
        elif '**' in pat:
            raise ValueError("Invalid pattern: '**' can only be an entire path component")
        elif _is_wildcard_pattern(pat):
            cls = _WildcardSelector
        else:
            cls = _PreciseSelector
        return cls(pat, child_parts)

    if hasattr(functools, "lru_cache"):
        _make_selector = functools.lru_cache()(_make_selector)

    class _Selector:
        """A selector matches a specific glob pattern part against the children
        of a given path."""

        def __init__(self, child_parts):
            self.child_parts = child_parts
            if child_parts:
                self.successor = _make_selector(child_parts)
                self.dironly = True
            else:
                self.successor = _TerminatingSelector()
                self.dironly = False

        def select_from(self, parent_path):
            """Iterate over all child paths of `parent_path` matched by this
            selector.  This can contain parent_path itself."""
            path_cls = type(parent_path)
            is_dir = path_cls.is_dir
            exists = path_cls.exists
            scandir = parent_path._accessor.scandir
            if not is_dir(parent_path):
                return iter([])
            return self._select_from(parent_path, is_dir, exists, scandir)

    class _TerminatingSelector:

        def _select_from(self, parent_path, is_dir, exists, scandir):
            yield parent_path

    class _PreciseSelector(_Selector):

        def __init__(self, name, child_parts):
            self.name = name
            _Selector.__init__(self, child_parts)

        def _select_from(self, parent_path, is_dir, exists, scandir):
            try:
                path = parent_path._make_child_relpath(self.name)
                if (is_dir if self.dironly else exists)(path):
                    for p in self.successor._select_from(path, is_dir, exists, scandir):
                        yield p
            except PermissionError:
                return

    class _WildcardSelector(_Selector):

        def __init__(self, pat, child_parts):
            self.pat = re.compile(fnmatch.translate(pat))
            _Selector.__init__(self, child_parts)

        def _select_from(self, parent_path, is_dir, exists, scandir):
            try:
                cf = parent_path._flavour.casefold
                entries = list(scandir(parent_path))
                for entry in entries:
                    entry_is_dir = False
                    try:
                        entry_is_dir = entry.is_dir()
                    except OSError as e:
                        if not _ignore_error(e):
                            raise
                    if not self.dironly or entry_is_dir:
                        name = entry.name
                        casefolded = cf(name)
                        if self.pat.match(casefolded):
                            path = parent_path._make_child_relpath(name)
                            for p in self.successor._select_from(path, is_dir, exists, scandir):
                                yield p
            except PermissionError:
                return

    class _RecursiveWildcardSelector(_Selector):

        def __init__(self, pat, child_parts):
            _Selector.__init__(self, child_parts)

        def _iterate_directories(self, parent_path, is_dir, scandir):
            yield parent_path
            try:
                entries = list(scandir(parent_path))
                for entry in entries:
                    entry_is_dir = False
                    try:
                        entry_is_dir = entry.is_dir()
                    except OSError as e:
                        if not _ignore_error(e):
                            raise
                    if entry_is_dir and not entry.is_symlink():
                        path = parent_path._make_child_relpath(entry.name)
                        for p in self._iterate_directories(path, is_dir, scandir):
                            yield p
            except PermissionError:
                return

        def _select_from(self, parent_path, is_dir, exists, scandir):
            try:
                yielded = set()
                try:
                    successor_select = self.successor._select_from
                    for starting_point in self._iterate_directories(parent_path, is_dir, scandir):
                        for p in successor_select(starting_point, is_dir, exists, scandir):
                            if p not in yielded:
                                yield p
                                yielded.add(p)
                finally:
                    yielded.clear()
            except PermissionError:
                return

    #
    # Public API
    #

    class _PathParents(Sequence):
        """This object provides sequence-like access to the logical ancestors
        of a path.  Don't try to construct it yourself."""
        __slots__ = ('_pathcls', '_drv', '_root', '_parts')

        def __init__(self, path):
            # We don't store the instance to avoid reference cycles
            self._pathcls = type(path)
            self._drv = path._drv
            self._root = path._root
            self._parts = path._parts

        def __len__(self):
            if self._drv or self._root:
                return len(self._parts) - 1
            else:
                return len(self._parts)

        def __getitem__(self, idx):
            if idx < 0 or idx >= len(self):
                raise IndexError(idx)
            return self._pathcls._from_parsed_parts(self._drv, self._root,
                                                    self._parts[:-idx - 1])

        def __repr__(self):
            return "<{}.parents>".format(self._pathcls.__name__)

    class PurePath(object):
        """Base class for manipulating paths without I/O.

        PurePath represents a filesystem path and offers operations which
        don't imply any actual filesystem I/O.  Depending on your system,
        instantiating a PurePath will return either a PurePosixPath or a
        PureWindowsPath object.  You can also instantiate either of these classes
        directly, regardless of your system.
        """
        __slots__ = (
            '_drv', '_root', '_parts',
            '_str', '_hash', '_pparts', '_cached_cparts',
        )

        def __new__(cls, *args):
            """Construct a PurePath from one or several strings and or existing
            PurePath objects.  The strings and path objects are combined so as
            to yield a canonicalized path, which is incorporated into the
            new PurePath object.
            """
            if cls is PurePath:
                cls = PureWindowsPath if os.name == 'nt' else PurePosixPath
            return cls._from_parts(args)

        def __reduce__(self):
            # Using the parts tuple helps share interned path parts
            # when pickling related paths.
            return (self.__class__, tuple(self._parts))

        @classmethod
        def _parse_args(cls, args):
            # This is useful when you don't want to create an instance, just
            # canonicalize some constructor arguments.
            parts = []
            for a in args:
                if isinstance(a, PurePath):
                    parts += a._parts
                else:
                    a = os.fspath(a)
                    if isinstance(a, str):
                        # Force-cast str subclasses to str (issue #21127)
                        parts.append(str(a))
                    else:
                        raise TypeError(
                            "argument should be a str object or an os.PathLike "
                            "object returning str, not %r"
                            % type(a))
            return cls._flavour.parse_parts(parts)

        @classmethod
        def _from_parts(cls, args, init=True):
            # We need to call _parse_args on the instance, so as to get the
            # right flavour.
            self = object.__new__(cls)
            drv, root, parts = self._parse_args(args)
            self._drv = drv
            self._root = root
            self._parts = parts
            if init:
                self._init()
            return self

        @classmethod
        def _from_parsed_parts(cls, drv, root, parts, init=True):
            self = object.__new__(cls)
            self._drv = drv
            self._root = root
            self._parts = parts
            if init:
                self._init()
            return self

        @classmethod
        def _format_parsed_parts(cls, drv, root, parts):
            if drv or root:
                return drv + root + cls._flavour.join(parts[1:])
            else:
                return cls._flavour.join(parts)

        def _init(self):
            # Overridden in concrete Path
            pass

        def _make_child(self, args):
            drv, root, parts = self._parse_args(args)
            drv, root, parts = self._flavour.join_parsed_parts(
                self._drv, self._root, self._parts, drv, root, parts)
            return self._from_parsed_parts(drv, root, parts)

        def __str__(self):
            """Return the string representation of the path, suitable for
            passing to system calls."""
            try:
                return self._str
            except AttributeError:
                self._str = self._format_parsed_parts(self._drv, self._root,
                                                      self._parts) or '.'
                return self._str

        def __fspath__(self):
            return str(self)

        def as_posix(self):
            """Return the string representation of the path with forward (/)
            slashes."""
            f = self._flavour
            return str(self).replace(f.sep, '/')

        def __bytes__(self):
            """Return the bytes representation of the path.  This is only
            recommended to use under Unix."""
            return os.fsencode(self)

        def __repr__(self):
            return "{}({!r})".format(self.__class__.__name__, self.as_posix())

        def as_uri(self):
            """Return the path as a 'file' URI."""
            if not self.is_absolute():
                raise ValueError("relative path can't be expressed as a file URI")
            return self._flavour.make_uri(self)

        @property
        def _cparts(self):
            # Cached casefolded parts, for hashing and comparison
            try:
                return self._cached_cparts
            except AttributeError:
                self._cached_cparts = self._flavour.casefold_parts(self._parts)
                return self._cached_cparts

        def __eq__(self, other):
            if not isinstance(other, PurePath):
                return NotImplemented
            return self._cparts == other._cparts and self._flavour is other._flavour

        def __hash__(self):
            try:
                return self._hash
            except AttributeError:
                self._hash = hash(tuple(self._cparts))
                return self._hash

        def __lt__(self, other):
            if not isinstance(other, PurePath) or self._flavour is not other._flavour:
                return NotImplemented
            return self._cparts < other._cparts

        def __le__(self, other):
            if not isinstance(other, PurePath) or self._flavour is not other._flavour:
                return NotImplemented
            return self._cparts <= other._cparts

        def __gt__(self, other):
            if not isinstance(other, PurePath) or self._flavour is not other._flavour:
                return NotImplemented
            return self._cparts > other._cparts

        def __ge__(self, other):
            if not isinstance(other, PurePath) or self._flavour is not other._flavour:
                return NotImplemented
            return self._cparts >= other._cparts

        drive = property(attrgetter('_drv'),
                         doc="""The drive prefix (letter or UNC path), if any.""")

        root = property(attrgetter('_root'),
                        doc="""The root of the path, if any.""")

        @property
        def anchor(self):
            """The concatenation of the drive and root, or ''."""
            anchor = self._drv + self._root
            return anchor

        @property
        def name(self):
            """The final path component, if any."""
            parts = self._parts
            if len(parts) == (1 if (self._drv or self._root) else 0):
                return ''
            return parts[-1]

        @property
        def suffix(self):
            """The final component's last suffix, if any."""
            name = self.name
            i = name.rfind('.')
            if 0 < i < len(name) - 1:
                return name[i:]
            else:
                return ''

        @property
        def suffixes(self):
            """A list of the final component's suffixes, if any."""
            name = self.name
            if name.endswith('.'):
                return []
            name = name.lstrip('.')
            return ['.' + suffix for suffix in name.split('.')[1:]]

        @property
        def stem(self):
            """The final path component, minus its last suffix."""
            name = self.name
            i = name.rfind('.')
            if 0 < i < len(name) - 1:
                return name[:i]
            else:
                return name

        def with_name(self, name):
            """Return a new path with the file name changed."""
            if not self.name:
                raise ValueError("%r has an empty name" % (self,))
            drv, root, parts = self._flavour.parse_parts((name,))
            if (not name or name[-1] in [self._flavour.sep, self._flavour.altsep]
                or drv or root or len(parts) != 1):
                raise ValueError("Invalid name %r" % (name))
            return self._from_parsed_parts(self._drv, self._root,
                                           self._parts[:-1] + [name])

        def with_suffix(self, suffix):
            """Return a new path with the file suffix changed.  If the path
            has no suffix, add given suffix.  If the given suffix is an empty
            string, remove the suffix from the path.
            """
            f = self._flavour
            if f.sep in suffix or f.altsep and f.altsep in suffix:
                raise ValueError("Invalid suffix %r" % (suffix,))
            if suffix and not suffix.startswith('.') or suffix == '.':
                raise ValueError("Invalid suffix %r" % (suffix))
            name = self.name
            if not name:
                raise ValueError("%r has an empty name" % (self,))
            old_suffix = self.suffix
            if not old_suffix:
                name = name + suffix
            else:
                name = name[:-len(old_suffix)] + suffix
            return self._from_parsed_parts(self._drv, self._root,
                                           self._parts[:-1] + [name])

        def relative_to(self, *other):
            """Return the relative path to another path identified by the passed
            arguments.  If the operation is not possible (because this is not
            a subpath of the other path), raise ValueError.
            """
            # For the purpose of this method, drive and root are considered
            # separate parts, i.e.:
            #   Path('c:/').relative_to('c:')  gives Path('/')
            #   Path('c:/').relative_to('/')   raise ValueError
            if not other:
                raise TypeError("need at least one argument")
            parts = self._parts
            drv = self._drv
            root = self._root
            if root:
                abs_parts = [drv, root] + parts[1:]
            else:
                abs_parts = parts
            to_drv, to_root, to_parts = self._parse_args(other)
            if to_root:
                to_abs_parts = [to_drv, to_root] + to_parts[1:]
            else:
                to_abs_parts = to_parts
            n = len(to_abs_parts)
            cf = self._flavour.casefold_parts
            if (root or drv) if n == 0 else cf(abs_parts[:n]) != cf(to_abs_parts):
                formatted = self._format_parsed_parts(to_drv, to_root, to_parts)
                raise ValueError("{!r} does not start with {!r}"
                                 .format(str(self), str(formatted)))
            return self._from_parsed_parts('', root if n == 1 else '',
                                           abs_parts[n:])

        @property
        def parts(self):
            """An object providing sequence-like access to the
            components in the filesystem path."""
            # We cache the tuple to avoid building a new one each time .parts
            # is accessed.  XXX is this necessary?
            try:
                return self._pparts
            except AttributeError:
                self._pparts = tuple(self._parts)
                return self._pparts

        def joinpath(self, *args):
            """Combine this path with one or several arguments, and return a
            new path representing either a subpath (if all arguments are relative
            paths) or a totally different path (if one of the arguments is
            anchored).
            """
            return self._make_child(args)

        def __truediv__(self, key):
            return self._make_child((key,))

        def __rtruediv__(self, key):
            return self._from_parts([key] + self._parts)

        @property
        def parent(self):
            """The logical parent of the path."""
            drv = self._drv
            root = self._root
            parts = self._parts
            if len(parts) == 1 and (drv or root):
                return self
            return self._from_parsed_parts(drv, root, parts[:-1])

        @property
        def parents(self):
            """A sequence of this path's logical parents."""
            return _PathParents(self)

        def is_absolute(self):
            """True if the path is absolute (has both a root and, if applicable,
            a drive)."""
            if not self._root:
                return False
            return not self._flavour.has_drv or bool(self._drv)

        def is_reserved(self):
            """Return True if the path contains one of the special names reserved
            by the system, if any."""
            return self._flavour.is_reserved(self._parts)

        def match(self, path_pattern):
            """
            Return True if this path matches the given pattern.
            """
            cf = self._flavour.casefold
            path_pattern = cf(path_pattern)
            drv, root, pat_parts = self._flavour.parse_parts((path_pattern,))
            if not pat_parts:
                raise ValueError("empty pattern")
            if drv and drv != cf(self._drv):
                return False
            if root and root != cf(self._root):
                return False
            parts = self._cparts
            if drv or root:
                if len(pat_parts) != len(parts):
                    return False
                pat_parts = pat_parts[1:]
            elif len(pat_parts) > len(parts):
                return False
            for part, pat in zip(reversed(parts), reversed(pat_parts)):
                if not fnmatch.fnmatchcase(part, pat):
                    return False
            return True

    # Can't subclass os.PathLike from PurePath and keep the constructor
    # optimizations in PurePath._parse_args().
    os.PathLike.register(PurePath)

    class PurePosixPath(PurePath):
        """PurePath subclass for non-Windows systems.

        On a POSIX system, instantiating a PurePath should return this object.
        However, you can also instantiate it directly on any system.
        """
        _flavour = _posix_flavour
        __slots__ = ()

    class PureWindowsPath(PurePath):
        """PurePath subclass for Windows systems.

        On a Windows system, instantiating a PurePath should return this object.
        However, you can also instantiate it directly on any system.
        """
        _flavour = _windows_flavour
        __slots__ = ()

    # Filesystem-accessing classes

    class Path(PurePath):
        """PurePath subclass that can make system calls.

        Path represents a filesystem path but unlike PurePath, also offers
        methods to do system calls on path objects. Depending on your system,
        instantiating a Path will return either a PosixPath or a WindowsPath
        object. You can also instantiate a PosixPath or WindowsPath directly,
        but cannot instantiate a WindowsPath on a POSIX system or vice versa.
        """
        __slots__ = (
            '_accessor',
            '_closed',
        )

        def __new__(cls, *args, **kwargs):
            if cls is Path:
                cls = WindowsPath if os.name == 'nt' else PosixPath
            self = cls._from_parts(args, init=False)
            if not self._flavour.is_supported:
                raise NotImplementedError("cannot instantiate %r on your system"
                                          % (cls.__name__,))
            self._init()
            return self

        def _init(self,
                  # Private non-constructor arguments
                  template=None,
                  ):
            self._closed = False
            if template is not None:
                self._accessor = template._accessor
            else:
                self._accessor = _normal_accessor

        def _make_child_relpath(self, part):
            # This is an optimization used for dir walking.  `part` must be
            # a single part relative to this path.
            parts = self._parts + [part]
            return self._from_parsed_parts(self._drv, self._root, parts)

        def __enter__(self):
            if self._closed:
                self._raise_closed()
            return self

        def __exit__(self, t, v, tb):
            self._closed = True

        def _raise_closed(self):
            raise ValueError("I/O operation on closed path")

        def _opener(self, name, flags, mode=0o666):
            # A stub for the opener argument to built-in open()
            return self._accessor.open(self, flags, mode)

        def _raw_open(self, flags, mode=0o777):
            """
            Open the file pointed by this path and return a file descriptor,
            as os.open() does.
            """
            if self._closed:
                self._raise_closed()
            return self._accessor.open(self, flags, mode)

        # Public API

        @classmethod
        def cwd(cls):
            """Return a new path pointing to the current working directory
            (as returned by os.getcwd()).
            """
            return cls(os.getcwd())

        @classmethod
        def home(cls):
            """Return a new path pointing to the user's home directory (as
            returned by os.path.expanduser('~')).
            """
            return cls(cls()._flavour.gethomedir(None))

        def samefile(self, other_path):
            """Return whether other_path is the same or not as this file
            (as returned by os.path.samefile()).
            """
            st = self.stat()
            try:
                other_st = other_path.stat()
            except AttributeError:
                other_st = os.stat(other_path)
            return os.path.samestat(st, other_st)

        def iterdir(self):
            """Iterate over the files in this directory.  Does not yield any
            result for the special paths '.' and '..'.
            """
            if self._closed:
                self._raise_closed()
            for name in self._accessor.listdir(self):
                if name in {'.', '..'}:
                    # Yielding a path object for these makes little sense
                    continue
                yield self._make_child_relpath(name)
                if self._closed:
                    self._raise_closed()

        def glob(self, pattern):
            """Iterate over this subtree and yield all existing files (of any
            kind, including directories) matching the given relative pattern.
            """
            if not pattern:
                raise ValueError("Unacceptable pattern: {!r}".format(pattern))
            pattern = self._flavour.casefold(pattern)
            drv, root, pattern_parts = self._flavour.parse_parts((pattern,))
            if drv or root:
                raise NotImplementedError("Non-relative patterns are unsupported")
            selector = _make_selector(tuple(pattern_parts))
            for p in selector.select_from(self):
                yield p

        def rglob(self, pattern):
            """Recursively yield all existing files (of any kind, including
            directories) matching the given relative pattern, anywhere in
            this subtree.
            """
            pattern = self._flavour.casefold(pattern)
            drv, root, pattern_parts = self._flavour.parse_parts((pattern,))
            if drv or root:
                raise NotImplementedError("Non-relative patterns are unsupported")
            selector = _make_selector(("**",) + tuple(pattern_parts))
            for p in selector.select_from(self):
                yield p

        def absolute(self):
            """Return an absolute version of this path.  This function works
            even if the path doesn't point to anything.

            No normalization is done, i.e. all '.' and '..' will be kept along.
            Use resolve() to get the canonical path to a file.
            """
            # XXX untested yet!
            if self._closed:
                self._raise_closed()
            if self.is_absolute():
                return self
            # FIXME this must defer to the specific flavour (and, under Windows,
            # use nt._getfullpathname())
            obj = self._from_parts([os.getcwd()] + self._parts, init=False)
            obj._init(template=self)
            return obj

        def resolve(self, strict=False):
            """
            Make the path absolute, resolving all symlinks on the way and also
            normalizing it (for example turning slashes into backslashes under
            Windows).
            """
            if self._closed:
                self._raise_closed()
            s = self._flavour.resolve(self, strict=strict)
            if s is None:
                # No symlink resolution => for consistency, raise an error if
                # the path doesn't exist or is forbidden
                self.stat()
                s = str(self.absolute())
            # Now we have no symlinks in the path, it's safe to normalize it.
            normed = self._flavour.pathmod.normpath(s)
            obj = self._from_parts((normed,), init=False)
            obj._init(template=self)
            return obj

        def stat(self):
            """
            Return the result of the stat() system call on this path, like
            os.stat() does.
            """
            return self._accessor.stat(self)

        def owner(self):
            """
            Return the login name of the file owner.
            """
            import pwd
            return pwd.getpwuid(self.stat().st_uid).pw_name

        def group(self):
            """
            Return the group name of the file gid.
            """
            import grp
            return grp.getgrgid(self.stat().st_gid).gr_name

        def open(self, mode='r', buffering=-1, encoding=None,
                 errors=None, newline=None):
            """
            Open the file pointed by this path and return a file object, as
            the built-in open() function does.
            """
            if self._closed:
                self._raise_closed()
            return io.open(self, mode, buffering, encoding, errors, newline,
                           opener=self._opener)

        def read_bytes(self):
            """
            Open the file in bytes mode, read it, and close the file.
            """
            with self.open(mode='rb') as f:
                return f.read()

        def read_text(self, encoding=None, errors=None):
            """
            Open the file in text mode, read it, and close the file.
            """
            with self.open(mode='r', encoding=encoding, errors=errors) as f:
                return f.read()

        def write_bytes(self, data):
            """
            Open the file in bytes mode, write to it, and close the file.
            """
            # type-check for the buffer interface before truncating the file
            view = memoryview(data)
            with self.open(mode='wb') as f:
                return f.write(view)

        def write_text(self, data, encoding=None, errors=None):
            """
            Open the file in text mode, write to it, and close the file.
            """
            if not isinstance(data, str):
                raise TypeError('data must be str, not %s' %
                                data.__class__.__name__)
            with self.open(mode='w', encoding=encoding, errors=errors) as f:
                return f.write(data)

        def touch(self, mode=0o666, exist_ok=True):
            """
            Create this file with the given access mode, if it doesn't exist.
            """
            if self._closed:
                self._raise_closed()
            if exist_ok:
                # First try to bump modification time
                # Implementation note: GNU touch uses the UTIME_NOW option of
                # the utimensat() / futimens() functions.
                try:
                    self._accessor.utime(self, None)
                except OSError:
                    # Avoid exception chaining
                    pass
                else:
                    return
            flags = os.O_CREAT | os.O_WRONLY
            if not exist_ok:
                flags |= os.O_EXCL
            fd = self._raw_open(flags, mode)
            os.close(fd)

        def mkdir(self, mode=0o777, parents=False, exist_ok=False):
            """
            Create a new directory at this given path.
            """
            if self._closed:
                self._raise_closed()
            try:
                self._accessor.mkdir(self, mode)
            except FileNotFoundError:
                if not parents or self.parent == self:
                    raise
                self.parent.mkdir(parents=True, exist_ok=True)
                self.mkdir(mode, parents=False, exist_ok=exist_ok)
            except OSError:
                # Cannot rely on checking for EEXIST, since the operating system
                # could give priority to other errors like EACCES or EROFS
                if not exist_ok or not self.is_dir():
                    raise

        def chmod(self, mode):
            """
            Change the permissions of the path, like os.chmod().
            """
            if self._closed:
                self._raise_closed()
            self._accessor.chmod(self, mode)

        def lchmod(self, mode):
            """
            Like chmod(), except if the path points to a symlink, the symlink's
            permissions are changed, rather than its target's.
            """
            if self._closed:
                self._raise_closed()
            self._accessor.lchmod(self, mode)

        def unlink(self):
            """
            Remove this file or link.
            If the path is a directory, use rmdir() instead.
            """
            if self._closed:
                self._raise_closed()
            self._accessor.unlink(self)

        def rmdir(self):
            """
            Remove this directory.  The directory must be empty.
            """
            if self._closed:
                self._raise_closed()
            self._accessor.rmdir(self)

        def lstat(self):
            """
            Like stat(), except if the path points to a symlink, the symlink's
            status information is returned, rather than its target's.
            """
            if self._closed:
                self._raise_closed()
            return self._accessor.lstat(self)

        def rename(self, target):
            """
            Rename this path to the given path.
            """
            if self._closed:
                self._raise_closed()
            self._accessor.rename(self, target)

        def replace(self, target):
            """
            Rename this path to the given path, clobbering the existing
            destination if it exists.
            """
            if self._closed:
                self._raise_closed()
            self._accessor.replace(self, target)

        def symlink_to(self, target, target_is_directory=False):
            """
            Make this path a symlink pointing to the given path.
            Note the order of arguments (self, target) is the reverse of os.symlink's.
            """
            if self._closed:
                self._raise_closed()
            self._accessor.symlink(target, self, target_is_directory)

        # Convenience functions for querying the stat results

        def exists(self):
            """
            Whether this path exists.
            """
            try:
                self.stat()
            except OSError as e:
                if not _ignore_error(e):
                    raise
                return False
            return True

        def is_dir(self):
            """
            Whether this path is a directory.
            """
            try:
                return S_ISDIR(self.stat().st_mode)
            except OSError as e:
                if not _ignore_error(e):
                    raise
                # Path doesn't exist or is a broken symlink
                # (see https://bitbucket.org/pitrou/pathlib/issue/12/)
                return False

        def is_file(self):
            """
            Whether this path is a regular file (also True for symlinks pointing
            to regular files).
            """
            try:
                return S_ISREG(self.stat().st_mode)
            except OSError as e:
                if not _ignore_error(e):
                    raise
                # Path doesn't exist or is a broken symlink
                # (see https://bitbucket.org/pitrou/pathlib/issue/12/)
                return False

        def is_mount(self):
            """
            Check if this path is a POSIX mount point
            """
            # Need to exist and be a dir
            if not self.exists() or not self.is_dir():
                return False

            parent = Path(self.parent)
            try:
                parent_dev = parent.stat().st_dev
            except OSError:
                return False

            dev = self.stat().st_dev
            if dev != parent_dev:
                return True
            ino = self.stat().st_ino
            parent_ino = parent.stat().st_ino
            return ino == parent_ino

        def is_symlink(self):
            """
            Whether this path is a symbolic link.
            """
            try:
                return S_ISLNK(self.lstat().st_mode)
            except OSError as e:
                if not _ignore_error(e):
                    raise
                # Path doesn't exist
                return False

        def is_block_device(self):
            """
            Whether this path is a block device.
            """
            try:
                return S_ISBLK(self.stat().st_mode)
            except OSError as e:
                if not _ignore_error(e):
                    raise
                # Path doesn't exist or is a broken symlink
                # (see https://bitbucket.org/pitrou/pathlib/issue/12/)
                return False

        def is_char_device(self):
            """
            Whether this path is a character device.
            """
            try:
                return S_ISCHR(self.stat().st_mode)
            except OSError as e:
                if not _ignore_error(e):
                    raise
                # Path doesn't exist or is a broken symlink
                # (see https://bitbucket.org/pitrou/pathlib/issue/12/)
                return False

        def is_fifo(self):
            """
            Whether this path is a FIFO.
            """
            try:
                return S_ISFIFO(self.stat().st_mode)
            except OSError as e:
                if not _ignore_error(e):
                    raise
                # Path doesn't exist or is a broken symlink
                # (see https://bitbucket.org/pitrou/pathlib/issue/12/)
                return False

        def is_socket(self):
            """
            Whether this path is a socket.
            """
            try:
                return S_ISSOCK(self.stat().st_mode)
            except OSError as e:
                if not _ignore_error(e):
                    raise
                # Path doesn't exist or is a broken symlink
                # (see https://bitbucket.org/pitrou/pathlib/issue/12/)
                return False

        def expanduser(self):
            """ Return a new path with expanded ~ and ~user constructs
            (as returned by os.path.expanduser)
            """
            if (not (self._drv or self._root) and
                self._parts and self._parts[0][:1] == '~'):
                homedir = self._flavour.gethomedir(self._parts[0][1:])
                return self._from_parts([homedir] + self._parts[1:])

            return self

    class PosixPath(Path, PurePosixPath):
        """Path subclass for non-Windows systems.

        On a POSIX system, instantiating a Path should return this object.
        """
        __slots__ = ()

    class WindowsPath(Path, PureWindowsPath):
        """Path subclass for Windows systems.

        On a Windows system, instantiating a Path should return this object.
        """
        __slots__ = ()

        def owner(self):
            raise NotImplementedError("Path.owner() is unsupported on this system")

        def group(self):
            raise NotImplementedError("Path.group() is unsupported on this system")

        def is_mount(self):
            raise NotImplementedError("Path.is_mount() is unsupported on this system")