Modules/posixmodule.c (part 7) — os.path

Source:

cpython 3.14 @ ab2d84fe1023/Lib/posixpath.py ↗

This annotation covers os.path (POSIX implementation). See modules_posix6_detail for os.stat, os.scandir, and DirEntry.

Map

Lines	Symbol	Role
1-80	os.path.join	Join path components
81-160	os.path.dirname / basename	Split path into head/tail
161-240	os.path.abspath	Canonicalize to absolute path
241-320	os.path.exists / isfile / isdir	Test path type
321-500	os.path.commonpath / relpath	Path relationships

Reading

os.path.join

# CPython: Lib/posixpath.py:76 join
def join(a, *p):
    a = os.fspath(a)
    sep = _get_sep(a)
    path = a
    for b in p:
        b = os.fspath(b)
        if b.startswith(sep):
            path = b  # Absolute component replaces everything
        elif not path or path.endswith(sep):
            path += b
        else:
            path += sep + b
    return path

os.path.join('/foo', 'bar', '/baz') returns '/baz': an absolute component resets the path. This matches the POSIX shell behavior of cd /foo; cd /baz ending at /baz.

os.path.abspath

# CPython: Lib/posixpath.py:374 abspath
def abspath(path):
    cwd = os.getcwd()
    return normpath(join(cwd, path))

def normpath(path):
    # Resolve . and .. components, remove double slashes
    initial_slashes = path.startswith('/')
    comps = path.split('/')
    new_comps = []
    for comp in comps:
        if comp in ('', '.'):
            continue
        if comp == '..' and new_comps and new_comps[-1] != '..':
            new_comps.pop()
        else:
            new_comps.append(comp)
    path = '/'.join(new_comps)
    return ('/' * initial_slashes) + path

abspath doesn't resolve symlinks (use realpath for that). It prepends os.getcwd() and normalizes .. and . components. normpath is deterministic without filesystem calls.

os.path.exists

# CPython: Lib/posixpath.py:166 exists
def exists(path):
    try:
        os.stat(path)
    except (OSError, ValueError):
        return False
    return True

exists catches OSError (no such file) and ValueError (bad path). It follows symlinks (use lexists for "does the symlink itself exist"). isfile additionally checks stat.S_ISREG(st.st_mode).

gopy notes

os.path.join is module/os.PathJoin in module/os/module.go. Uses path/filepath.Join with POSIX semantics. abspath calls os.Getwd() then filepath.Join. exists calls os.Stat and returns false on error. isfile checks !info.IsDir().