path: root/Lib/pathlib/__init__.py

"""Object-oriented filesystem paths.

This module provides classes to represent abstract paths and concrete
paths with operations that have semantics appropriate for different
operating systems.
"""

import io
import ntpath
import os
import posixpath
import sys
import warnings
from itertools import chain
from _collections_abc import Sequence

try:
    import pwd
except ImportError:
    pwd = None
try:
    import grp
except ImportError:
    grp = None

from . import _abc


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


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

    def __init__(self, path):
        self._path = path
        self._drv = path.drive
        self._root = path.root
        self._tail = path._tail

    def __len__(self):
        return len(self._tail)

    def __getitem__(self, idx):
        if isinstance(idx, slice):
            return tuple(self[i] for i in range(*idx.indices(len(self))))

        if idx >= len(self) or idx < -len(self):
            raise IndexError(idx)
        if idx < 0:
            idx += len(self)
        return self._path._from_parsed_parts(self._drv, self._root,
                                             self._tail[:-idx - 1])

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


UnsupportedOperation = _abc.UnsupportedOperation


class PurePath(_abc.PurePathBase):
    """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__ = (
        # The `_drv`, `_root` and `_tail_cached` slots store parsed and
        # normalized parts of the path. They are set when any of the `drive`,
        # `root` or `_tail` properties are accessed for the first time. The
        # three-part division corresponds to the result of
        # `os.path.splitroot()`, except that the tail is further split on path
        # separators (i.e. it is a list of strings), and that the root and
        # tail are normalized.
        '_drv', '_root', '_tail_cached',

        # The `_str` slot stores the string representation of the path,
        # computed from the drive, root and tail when `__str__()` is called
        # for the first time. It's used to implement `_str_normcase`
        '_str',

        # The `_str_normcase_cached` slot stores the string path with
        # normalized case. It is set when the `_str_normcase` property is
        # accessed for the first time. It's used to implement `__eq__()`
        # `__hash__()`, and `_parts_normcase`
        '_str_normcase_cached',

        # The `_parts_normcase_cached` slot stores the case-normalized
        # string path after splitting on path separators. It's set when the
        # `_parts_normcase` property is accessed for the first time. It's used
        # to implement comparison methods like `__lt__()`.
        '_parts_normcase_cached',

        # The `_hash` slot stores the hash of the case-normalized string
        # path. It's set when `__hash__()` is called for the first time.
        '_hash',
    )
    pathmod = os.path

    def __new__(cls, *args, **kwargs):
        """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 object.__new__(cls)

    def __init__(self, *args):
        paths = []
        for arg in args:
            if isinstance(arg, PurePath):
                if arg.pathmod is ntpath and self.pathmod is posixpath:
                    # GH-103631: Convert separators for backwards compatibility.
                    paths.extend(path.replace('\\', '/') for path in arg._raw_paths)
                else:
                    paths.extend(arg._raw_paths)
            else:
                try:
                    path = os.fspath(arg)
                except TypeError:
                    path = arg
                if not isinstance(path, str):
                    raise TypeError(
                        "argument should be a str or an os.PathLike "
                        "object where __fspath__ returns a str, "
                        f"not {type(path).__name__!r}")
                paths.append(path)
        # Avoid calling super().__init__, as an optimisation
        self._raw_paths = paths

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

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

    def __fspath__(self):
        return str(self)

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

    @property
    def _str_normcase(self):
        # String with normalized case, for hashing and equality checks
        try:
            return self._str_normcase_cached
        except AttributeError:
            if _abc._is_case_sensitive(self.pathmod):
                self._str_normcase_cached = str(self)
            else:
                self._str_normcase_cached = str(self).lower()
            return self._str_normcase_cached

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

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

    @property
    def _parts_normcase(self):
        # Cached parts with normalized case, for comparisons.
        try:
            return self._parts_normcase_cached
        except AttributeError:
            self._parts_normcase_cached = self._str_normcase.split(self.pathmod.sep)
            return self._parts_normcase_cached

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

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

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

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

    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.drive, self.root,
                                                  self._tail) or '.'
            return self._str

    @classmethod
    def _format_parsed_parts(cls, drv, root, tail):
        if drv or root:
            return drv + root + cls.pathmod.sep.join(tail)
        elif tail and cls.pathmod.splitdrive(tail[0])[0]:
            tail = ['.'] + tail
        return cls.pathmod.sep.join(tail)

    def _from_parsed_parts(self, drv, root, tail):
        path_str = self._format_parsed_parts(drv, root, tail)
        path = self.with_segments(path_str)
        path._str = path_str or '.'
        path._drv = drv
        path._root = root
        path._tail_cached = tail
        return path

    @classmethod
    def _parse_path(cls, path):
        if not path:
            return '', '', []
        sep = cls.pathmod.sep
        altsep = cls.pathmod.altsep
        if altsep:
            path = path.replace(altsep, sep)
        drv, root, rel = cls.pathmod.splitroot(path)
        if not root and drv.startswith(sep) and not drv.endswith(sep):
            drv_parts = drv.split(sep)
            if len(drv_parts) == 4 and drv_parts[2] not in '?.':
                # e.g. //server/share
                root = sep
            elif len(drv_parts) == 6:
                # e.g. //?/unc/server/share
                root = sep
        parsed = [sys.intern(str(x)) for x in rel.split(sep) if x and x != '.']
        return drv, root, parsed

    @property
    def _raw_path(self):
        """The joined but unnormalized path."""
        paths = self._raw_paths
        if len(paths) == 0:
            path = ''
        elif len(paths) == 1:
            path = paths[0]
        else:
            path = self.pathmod.join(*paths)
        return path

    @property
    def drive(self):
        """The drive prefix (letter or UNC path), if any."""
        try:
            return self._drv
        except AttributeError:
            self._drv, self._root, self._tail_cached = self._parse_path(self._raw_path)
            return self._drv

    @property
    def root(self):
        """The root of the path, if any."""
        try:
            return self._root
        except AttributeError:
            self._drv, self._root, self._tail_cached = self._parse_path(self._raw_path)
            return self._root

    @property
    def _tail(self):
        try:
            return self._tail_cached
        except AttributeError:
            self._drv, self._root, self._tail_cached = self._parse_path(self._raw_path)
            return self._tail_cached

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

    @property
    def parts(self):
        """An object providing sequence-like access to the
        components in the filesystem path."""
        if self.drive or self.root:
            return (self.drive + self.root,) + tuple(self._tail)
        else:
            return tuple(self._tail)

    @property
    def parent(self):
        """The logical parent of the path."""
        drv = self.drive
        root = self.root
        tail = self._tail
        if not tail:
            return self
        return self._from_parsed_parts(drv, root, tail[:-1])

    @property
    def parents(self):
        """A sequence of this path's logical parents."""
        # The value of this property should not be cached on the path object,
        # as doing so would introduce a reference cycle.
        return _PathParents(self)

    @property
    def name(self):
        """The final path component, if any."""
        tail = self._tail
        if not tail:
            return ''
        return tail[-1]

    def with_name(self, name):
        """Return a new path with the file name changed."""
        m = self.pathmod
        if not name or m.sep in name or (m.altsep and m.altsep in name) or name == '.':
            raise ValueError(f"Invalid name {name!r}")
        tail = self._tail.copy()
        if not tail:
            raise ValueError(f"{self!r} has an empty name")
        tail[-1] = name
        return self._from_parsed_parts(self.drive, self.root, tail)

    def relative_to(self, other, /, *_deprecated, walk_up=False):
        """Return the relative path to another path identified by the passed
        arguments.  If the operation is not possible (because this is not
        related to the other path), raise ValueError.

        The *walk_up* parameter controls whether `..` may be used to resolve
        the path.
        """
        if _deprecated:
            msg = ("support for supplying more than one positional argument "
                   "to pathlib.PurePath.relative_to() is deprecated and "
                   "scheduled for removal in Python 3.14")
            warnings.warn(msg, DeprecationWarning, stacklevel=2)
            other = self.with_segments(other, *_deprecated)
        elif not isinstance(other, PurePath):
            other = self.with_segments(other)
        for step, path in enumerate(chain([other], other.parents)):
            if path == self or path in self.parents:
                break
            elif not walk_up:
                raise ValueError(f"{str(self)!r} is not in the subpath of {str(other)!r}")
            elif path.name == '..':
                raise ValueError(f"'..' segment in {str(other)!r} cannot be walked")
        else:
            raise ValueError(f"{str(self)!r} and {str(other)!r} have different anchors")
        parts = ['..'] * step + self._tail[len(path._tail):]
        return self._from_parsed_parts('', '', parts)

    def is_relative_to(self, other, /, *_deprecated):
        """Return True if the path is relative to another path or False.
        """
        if _deprecated:
            msg = ("support for supplying more than one argument to "
                   "pathlib.PurePath.is_relative_to() is deprecated and "
                   "scheduled for removal in Python 3.14")
            warnings.warn(msg, DeprecationWarning, stacklevel=2)
            other = self.with_segments(other, *_deprecated)
        elif not isinstance(other, PurePath):
            other = self.with_segments(other)
        return other == self or other in self.parents

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

        drive = self.drive
        if len(drive) == 2 and drive[1] == ':':
            # It's a path on a local drive => 'file:///c:/a/b'
            prefix = 'file:///' + drive
            path = self.as_posix()[2:]
        elif drive:
            # It's a path on a network drive => 'file://host/share/a/b'
            prefix = 'file:'
            path = self.as_posix()
        else:
            # It's a posix path => 'file:///etc/hosts'
            prefix = 'file://'
            path = str(self)
        from urllib.parse import quote_from_bytes
        return prefix + quote_from_bytes(os.fsencode(path))


# Subclassing os.PathLike makes isinstance() checks slower,
# which in turn makes Path construction slower. Register instead!
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.
    """
    pathmod = posixpath
    __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.
    """
    pathmod = ntpath
    __slots__ = ()


class Path(_abc.PathBase, 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__ = ()
    as_uri = PurePath.as_uri

    @classmethod
    def _unsupported(cls, method_name):
        msg = f"{cls.__name__}.{method_name}() is unsupported on this system"
        raise UnsupportedOperation(msg)

    def __init__(self, *args, **kwargs):
        if kwargs:
            msg = ("support for supplying keyword arguments to pathlib.PurePath "
                   "is deprecated and scheduled for removal in Python {remove}")
            warnings._deprecated("pathlib.PurePath(**kwargs)", msg, remove=(3, 14))
        super().__init__(*args)

    def __new__(cls, *args, **kwargs):
        if cls is Path:
            cls = WindowsPath if os.name == 'nt' else PosixPath
        return object.__new__(cls)

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

    def is_mount(self):
        """
        Check if this path is a mount point
        """
        return os.path.ismount(self)

    def is_junction(self):
        """
        Whether this path is a junction.
        """
        return os.path.isjunction(self)

    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 "b" not in mode:
            encoding = io.text_encoding(encoding)
        return io.open(self, mode, buffering, encoding, errors, newline)

    def read_text(self, encoding=None, errors=None, newline=None):
        """
        Open the file in text mode, read it, and close the file.
        """
        # Call io.text_encoding() here to ensure any warning is raised at an
        # appropriate stack level.
        encoding = io.text_encoding(encoding)
        return _abc.PathBase.read_text(self, encoding, errors, newline)

    def write_text(self, data, encoding=None, errors=None, newline=None):
        """
        Open the file in text mode, write to it, and close the file.
        """
        # Call io.text_encoding() here to ensure any warning is raised at an
        # appropriate stack level.
        encoding = io.text_encoding(encoding)
        return _abc.PathBase.write_text(self, data, encoding, errors, newline)

    def iterdir(self):
        """Yield path objects of the directory contents.

        The children are yielded in arbitrary order, and the
        special entries '.' and '..' are not included.
        """
        return (self._make_child_relpath(name) for name in os.listdir(self))

    def _scandir(self):
        return os.scandir(self)

    def _make_child_entry(self, entry, is_dir=False):
        # Transform an entry yielded from _scandir() into a path object.
        path_str = entry.name if str(self) == '.' else entry.path
        path = self.with_segments(path_str)
        path._str = path_str
        path._drv = self.drive
        path._root = self.root
        path._tail_cached = self._tail + [entry.name]
        return path

    def _make_child_relpath(self, name):
        path_str = str(self)
        tail = self._tail
        if tail:
            path_str = f'{path_str}{self.pathmod.sep}{name}'
        elif path_str != '.':
            path_str = f'{path_str}{name}'
        else:
            path_str = name
        path = self.with_segments(path_str)
        path._str = path_str
        path._drv = self.drive
        path._root = self.root
        path._tail_cached = tail + [name]
        return path

    def glob(self, pattern, *, case_sensitive=None, follow_symlinks=None):
        """Iterate over this subtree and yield all existing files (of any
        kind, including directories) matching the given relative pattern.
        """
        sys.audit("pathlib.Path.glob", self, pattern)
        if pattern.endswith('**'):
            # GH-70303: '**' only matches directories. Add trailing slash.
            warnings.warn(
                "Pattern ending '**' will match files and directories in a "
                "future Python release. Add a trailing slash to match only "
                "directories and remove this warning.",
                FutureWarning, 2)
            pattern = f'{pattern}/'
        return _abc.PathBase.glob(
            self, pattern, case_sensitive=case_sensitive, follow_symlinks=follow_symlinks)

    def rglob(self, pattern, *, case_sensitive=None, follow_symlinks=None):
        """Recursively yield all existing files (of any kind, including
        directories) matching the given relative pattern, anywhere in
        this subtree.
        """
        sys.audit("pathlib.Path.rglob", self, pattern)
        if pattern.endswith('**'):
            # GH-70303: '**' only matches directories. Add trailing slash.
            warnings.warn(
                "Pattern ending '**' will match files and directories in a "
                "future Python release. Add a trailing slash to match only "
                "directories and remove this warning.",
                FutureWarning, 2)
            pattern = f'{pattern}/'
        pattern = f'**/{pattern}'
        return _abc.PathBase.glob(
            self, pattern, case_sensitive=case_sensitive, follow_symlinks=follow_symlinks)

    def walk(self, top_down=True, on_error=None, follow_symlinks=False):
        """Walk the directory tree from this directory, similar to os.walk()."""
        sys.audit("pathlib.Path.walk", self, on_error, follow_symlinks)
        return _abc.PathBase.walk(
            self, top_down=top_down, on_error=on_error, follow_symlinks=follow_symlinks)

    def absolute(self):
        """Return an absolute version of this path
        No normalization or symlink resolution is performed.

        Use resolve() to resolve symlinks and remove '..' segments.
        """
        if self.is_absolute():
            return self
        if self.root:
            drive = os.path.splitroot(os.getcwd())[0]
            return self._from_parsed_parts(drive, self.root, self._tail)
        if self.drive:
            # There is a CWD on each drive-letter drive.
            cwd = os.path.abspath(self.drive)
        else:
            cwd = os.getcwd()
        if not self._tail:
            # Fast path for "empty" paths, e.g. Path("."), Path("") or Path().
            # We pass only one argument to with_segments() to avoid the cost
            # of joining, and we exploit the fact that getcwd() returns a
            # fully-normalized string by storing it in _str. This is used to
            # implement Path.cwd().
            result = self.with_segments(cwd)
            result._str = cwd
            return result
        drive, root, rel = os.path.splitroot(cwd)
        if not rel:
            return self._from_parsed_parts(drive, root, self._tail)
        tail = rel.split(self.pathmod.sep)
        tail.extend(self._tail)
        return self._from_parsed_parts(drive, root, tail)

    def resolve(self, strict=False):
        """
        Make the path absolute, resolving all symlinks on the way and also
        normalizing it.
        """

        return self.with_segments(os.path.realpath(self, strict=strict))

    if pwd:
        def owner(self, *, follow_symlinks=True):
            """
            Return the login name of the file owner.
            """
            uid = self.stat(follow_symlinks=follow_symlinks).st_uid
            return pwd.getpwuid(uid).pw_name

    if grp:
        def group(self, *, follow_symlinks=True):
            """
            Return the group name of the file gid.
            """
            gid = self.stat(follow_symlinks=follow_symlinks).st_gid
            return grp.getgrgid(gid).gr_name

    if hasattr(os, "readlink"):
        def readlink(self):
            """
            Return the path to which the symbolic link points.
            """
            return self.with_segments(os.readlink(self))

    def touch(self, mode=0o666, exist_ok=True):
        """
        Create this file with the given access mode, if it doesn't exist.
        """

        if exist_ok:
            # First try to bump modification time
            # Implementation note: GNU touch uses the UTIME_NOW option of
            # the utimensat() / futimens() functions.
            try:
                os.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 = os.open(self, flags, mode)
        os.close(fd)

    def mkdir(self, mode=0o777, parents=False, exist_ok=False):
        """
        Create a new directory at this given path.
        """
        try:
            os.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, *, follow_symlinks=True):
        """
        Change the permissions of the path, like os.chmod().
        """
        os.chmod(self, mode, follow_symlinks=follow_symlinks)

    def unlink(self, missing_ok=False):
        """
        Remove this file or link.
        If the path is a directory, use rmdir() instead.
        """
        try:
            os.unlink(self)
        except FileNotFoundError:
            if not missing_ok:
                raise

    def rmdir(self):
        """
        Remove this directory.  The directory must be empty.
        """
        os.rmdir(self)

    def rename(self, target):
        """
        Rename this path to the target path.

        The target path may be absolute or relative. Relative paths are
        interpreted relative to the current working directory, *not* the
        directory of the Path object.

        Returns the new Path instance pointing to the target path.
        """
        os.rename(self, target)
        return self.with_segments(target)

    def replace(self, target):
        """
        Rename this path to the target path, overwriting if that path exists.

        The target path may be absolute or relative. Relative paths are
        interpreted relative to the current working directory, *not* the
        directory of the Path object.

        Returns the new Path instance pointing to the target path.
        """
        os.replace(self, target)
        return self.with_segments(target)

    if hasattr(os, "symlink"):
        def symlink_to(self, target, target_is_directory=False):
            """
            Make this path a symlink pointing to the target path.
            Note the order of arguments (link, target) is the reverse of os.symlink.
            """
            os.symlink(target, self, target_is_directory)

    if hasattr(os, "link"):
        def hardlink_to(self, target):
            """
            Make this path a hard link pointing to the same file as *target*.

            Note the order of arguments (self, target) is the reverse of os.link's.
            """
            os.link(target, self)

    def expanduser(self):
        """ Return a new path with expanded ~ and ~user constructs
        (as returned by os.path.expanduser)
        """
        if (not (self.drive or self.root) and
            self._tail and self._tail[0][:1] == '~'):
            homedir = os.path.expanduser(self._tail[0])
            if homedir[:1] == "~":
                raise RuntimeError("Could not determine home directory.")
            drv, root, tail = self._parse_path(homedir)
            return self._from_parsed_parts(drv, root, tail + self._tail[1:])

        return self

    @classmethod
    def from_uri(cls, uri):
        """Return a new path from the given 'file' URI."""
        if not uri.startswith('file:'):
            raise ValueError(f"URI does not start with 'file:': {uri!r}")
        path = uri[5:]
        if path[:3] == '///':
            # Remove empty authority
            path = path[2:]
        elif path[:12] == '//localhost/':
            # Remove 'localhost' authority
            path = path[11:]
        if path[:3] == '///' or (path[:1] == '/' and path[2:3] in ':|'):
            # Remove slash before DOS device/UNC path
            path = path[1:]
        if path[1:2] == '|':
            # Replace bar with colon in DOS drive
            path = path[:1] + ':' + path[2:]
        from urllib.parse import unquote_to_bytes
        path = cls(os.fsdecode(unquote_to_bytes(path)))
        if not path.is_absolute():
            raise ValueError(f"URI is not absolute: {uri!r}")
        return path


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

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

    if os.name == 'nt':
        def __new__(cls, *args, **kwargs):
            raise UnsupportedOperation(
                f"cannot instantiate {cls.__name__!r} on your system")

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

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

    if os.name != 'nt':
        def __new__(cls, *args, **kwargs):
            raise UnsupportedOperation(
                f"cannot instantiate {cls.__name__!r} on your system")