Edit: posixpath.py
"""Common operations on Posix pathnames. Instead of importing this module directly, import os and refer to this module as os.path. The "os.path" name is an alias for this module on Posix systems; on other systems (e.g. Mac, Windows), os.path provides the same operations in a manner specific to that platform, and is an alias to another module (e.g. macpath, ntpath). Some of this can actually be useful on non-Posix systems too, e.g. for manipulation of the pathname component of URLs. """ import os import sys import stat import genericpath from genericpath import * __all__ = ["normcase","isabs","join","splitdrive","split","splitext", "basename","dirname","commonprefix","getsize","getmtime", "getatime","getctime","islink","exists","lexists","isdir","isfile", "ismount", "expanduser","expandvars","normpath","abspath", "samefile","sameopenfile","samestat", "curdir","pardir","sep","pathsep","defpath","altsep","extsep", "devnull","realpath","supports_unicode_filenames","relpath"] # Strings representing various path-related bits and pieces. # These are primarily for export; internally, they are hardcoded. curdir = '.' pardir = '..' extsep = '.' sep = '/' pathsep = ':' defpath = ':/bin:/usr/bin' altsep = None devnull = '/dev/null' def _get_sep(path): if isinstance(path, bytes): return b'/' else: return '/' # Normalize the case of a pathname. Trivial in Posix, string.lower on Mac. # On MS-DOS this may also turn slashes into backslashes; however, other # normalizations (such as optimizing '../' away) are not allowed # (another function should be defined to do that). def normcase(s): """Normalize case of pathname. Has no effect under Posix""" # TODO: on Mac OS X, this should really return s.lower(). if not isinstance(s, (bytes, str)): raise TypeError("normcase() argument must be str or bytes, " "not '{}'".format(s.__class__.__name__)) return s # Return whether a path is absolute. # Trivial in Posix, harder on the Mac or MS-DOS. def isabs(s): """Test whether a path is absolute""" sep = _get_sep(s) return s.startswith(sep) # Join pathnames. # Ignore the previous parts if a part is absolute. # Insert a '/' unless the first part is empty or already ends in '/'. def join(a, *p): """Join two or more pathname components, inserting '/' as needed. If any component is an absolute path, all previous path components will be discarded. An empty last part will result in a path that ends with a separator.""" sep = _get_sep(a) path = a try: for b in p: if b.startswith(sep): path = b elif not path or path.endswith(sep): path += b else: path += sep + b except TypeError: valid_types = all(isinstance(s, (str, bytes, bytearray)) for s in (a, ) + p) if valid_types: # Must have a mixture of text and binary data raise TypeError("Can't mix strings and bytes in path " "components.") from None raise return path # Split a path in head (everything up to the last '/') and tail (the # rest). If the path ends in '/', tail will be empty. If there is no # '/' in the path, head will be empty. # Trailing '/'es are stripped from head unless it is the root. def split(p): """Split a pathname. Returns tuple "(head, tail)" where "tail" is everything after the final slash. Either part may be empty.""" sep = _get_sep(p) i = p.rfind(sep) + 1 head, tail = p[:i], p[i:] if head and head != sep*len(head): head = head.rstrip(sep) return head, tail # Split a path in root and extension. # The extension is everything starting at the last dot in the last # pathname component; the root is everything before that. # It is always true that root + ext == p. def splitext(p): if isinstance(p, bytes): sep = b'/' extsep = b'.' else: sep = '/' extsep = '.' return genericpath._splitext(p, sep, None, extsep) splitext.__doc__ = genericpath._splitext.__doc__ # Split a pathname into a drive specification and the rest of the # path. Useful on DOS/Windows/NT; on Unix, the drive is always empty. def splitdrive(p): """Split a pathname into drive and path. On Posix, drive is always empty.""" return p[:0], p # Return the tail (basename) part of a path, same as split(path)[1]. def basename(p): """Returns the final component of a pathname""" sep = _get_sep(p) i = p.rfind(sep) + 1 return p[i:] # Return the head (dirname) part of a path, same as split(path)[0]. def dirname(p): """Returns the directory component of a pathname""" sep = _get_sep(p) i = p.rfind(sep) + 1 head = p[:i] if head and head != sep*len(head): head = head.rstrip(sep) return head # Is a path a symbolic link? # This will always return false on systems where os.lstat doesn't exist. def islink(path): """Test whether a path is a symbolic link""" try: st = os.lstat(path) except (os.error, AttributeError): return False return stat.S_ISLNK(st.st_mode) # Being true for dangling symbolic links is also useful. def lexists(path): """Test whether a path exists. Returns True for broken symbolic links""" try: os.lstat(path) except os.error: return False return True # Are two filenames really pointing to the same file? def samefile(f1, f2): """Test whether two pathnames reference the same actual file""" s1 = os.stat(f1) s2 = os.stat(f2) return samestat(s1, s2) # Are two open files really referencing the same file? # (Not necessarily the same file descriptor!) def sameopenfile(fp1, fp2): """Test whether two open file objects reference the same file""" s1 = os.fstat(fp1) s2 = os.fstat(fp2) return samestat(s1, s2) # Are two stat buffers (obtained from stat, fstat or lstat) # describing the same file? def samestat(s1, s2): """Test whether two stat buffers reference the same file""" return s1.st_ino == s2.st_ino and \ s1.st_dev == s2.st_dev # Is a path a mount point? # (Does this work for all UNIXes? Is it even guaranteed to work by Posix?) def ismount(path): """Test whether a path is a mount point""" if islink(path): # A symlink can never be a mount point return False try: s1 = os.lstat(path) if isinstance(path, bytes): parent = join(path, b'..') else: parent = join(path, '..') s2 = os.lstat(parent) except os.error: return False # It doesn't exist -- so not a mount point :-) dev1 = s1.st_dev dev2 = s2.st_dev if dev1 != dev2: return True # path/.. on a different device as path ino1 = s1.st_ino ino2 = s2.st_ino if ino1 == ino2: return True # path/.. is the same i-node as path return False # Expand paths beginning with '~' or '~user'. # '~' means $HOME; '~user' means that user's home directory. # If the path doesn't begin with '~', or if the user or $HOME is unknown, # the path is returned unchanged (leaving error reporting to whatever # function is called with the expanded path as argument). # See also module 'glob' for expansion of *, ? and [...] in pathnames. # (A function should also be defined to do full *sh-style environment # variable expansion.) def expanduser(path): """Expand ~ and ~user constructions. If user or $HOME is unknown, do nothing.""" if isinstance(path, bytes): tilde = b'~' else: tilde = '~' if not path.startswith(tilde): return path sep = _get_sep(path) i = path.find(sep, 1) if i < 0: i = len(path) if i == 1: if 'HOME' not in os.environ: import pwd userhome = pwd.getpwuid(os.getuid()).pw_dir else: userhome = os.environ['HOME'] else: import pwd name = path[1:i] if isinstance(name, bytes): name = str(name, 'ASCII') try: pwent = pwd.getpwnam(name) except KeyError: return path userhome = pwent.pw_dir if isinstance(path, bytes): userhome = os.fsencode(userhome) root = b'/' else: root = '/' userhome = userhome.rstrip(root) return (userhome + path[i:]) or root # Expand paths containing shell variable substitutions. # This expands the forms $variable and ${variable} only. # Non-existent variables are left unchanged. _varprog = None _varprogb = None def expandvars(path): """Expand shell variables of form $var and ${var}. Unknown variables are left unchanged.""" global _varprog, _varprogb if isinstance(path, bytes): if b'$' not in path: return path if not _varprogb: import re _varprogb = re.compile(br'\$(\w+|\{[^}]*\})', re.ASCII) search = _varprogb.search start = b'{' end = b'}' environ = getattr(os, 'environb', None) else: if '$' not in path: return path if not _varprog: import re _varprog = re.compile(r'\$(\w+|\{[^}]*\})', re.ASCII) search = _varprog.search start = '{' end = '}' environ = os.environ i = 0 while True: m = search(path, i) if not m: break i, j = m.span(0) name = m.group(1) if name.startswith(start) and name.endswith(end): name = name[1:-1] try: if environ is None: value = os.fsencode(os.environ[os.fsdecode(name)]) else: value = environ[name] except KeyError: i = j else: tail = path[j:] path = path[:i] + value i = len(path) path += tail return path # Normalize a path, e.g. A//B, A/./B and A/foo/../B all become A/B. # It should be understood that this may change the meaning of the path # if it contains symbolic links! def normpath(path): """Normalize path, eliminating double slashes, etc.""" if isinstance(path, bytes): sep = b'/' empty = b'' dot = b'.' dotdot = b'..' else: sep = '/' empty = '' dot = '.' dotdot = '..' if path == empty: return dot initial_slashes = path.startswith(sep) # POSIX allows one or two initial slashes, but treats three or more # as single slash. if (initial_slashes and path.startswith(sep*2) and not path.startswith(sep*3)): initial_slashes = 2 comps = path.split(sep) new_comps = [] for comp in comps: if comp in (empty, dot): continue if (comp != dotdot or (not initial_slashes and not new_comps) or (new_comps and new_comps[-1] == dotdot)): new_comps.append(comp) elif new_comps: new_comps.pop() comps = new_comps path = sep.join(comps) if initial_slashes: path = sep*initial_slashes + path return path or dot def abspath(path): """Return an absolute path.""" if not isabs(path): if isinstance(path, bytes): cwd = os.getcwdb() else: cwd = os.getcwd() path = join(cwd, path) return normpath(path) # Return a canonical path (i.e. the absolute location of a file on the # filesystem). def realpath(filename): """Return the canonical path of the specified filename, eliminating any symbolic links encountered in the path.""" path, ok = _joinrealpath(filename[:0], filename, {}) return abspath(path) # Join two paths, normalizing ang eliminating any symbolic links # encountered in the second path. def _joinrealpath(path, rest, seen): if isinstance(path, bytes): sep = b'/' curdir = b'.' pardir = b'..' else: sep = '/' curdir = '.' pardir = '..' if isabs(rest): rest = rest[1:] path = sep while rest: name, _, rest = rest.partition(sep) if not name or name == curdir: # current dir continue if name == pardir: # parent dir if path: path, name = split(path) if name == pardir: path = join(path, pardir, pardir) else: path = pardir continue newpath = join(path, name) if not islink(newpath): path = newpath continue # Resolve the symbolic link 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. # Return already resolved part + rest of the path unchanged. return join(newpath, rest), False seen[newpath] = None # not resolved symlink path, ok = _joinrealpath(path, os.readlink(newpath), seen) if not ok: return join(path, rest), False seen[newpath] = path # resolved symlink return path, True supports_unicode_filenames = (sys.platform == 'darwin') def relpath(path, start=None): """Return a relative version of a path""" if not path: raise ValueError("no path specified") if isinstance(path, bytes): curdir = b'.' sep = b'/' pardir = b'..' else: curdir = '.' sep = '/' pardir = '..' if start is None: start = curdir start_list = [x for x in abspath(start).split(sep) if x] path_list = [x for x in abspath(path).split(sep) if x] # Work out how much of the filepath is shared by start and path. i = len(commonprefix([start_list, path_list])) rel_list = [pardir] * (len(start_list)-i) + path_list[i:] if not rel_list: return curdir return join(*rel_list)
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