bpo-15221: Update os.path.is*() documentation (GH-5185) (GH-5186)

`os.path.is*()` can return False if the file can't be accessed.
The behaviour is documented in details in `os.path.exists()`.
Link to `os.path.exists()` from `os.path.is*()`.
(cherry picked from commit b3dd18d4035803b50c65a434955966d1b3b1f363)

diff --git a/Doc/library/os.path.rst b/Doc/library/os.path.rst
index 406054e5d7a39ca627887bb51ac1e48313588f7d..06493f9505d31fb25f28b6c0989be691ab4163c2 100644 (file)
--- a/Doc/library/os.path.rst
+++ b/Doc/library/os.path.rst
@@ -246,8 +246,9 @@ the :mod:`glob` module.)
 
 .. function:: isfile(path)
 
-   Return ``True`` if *path* is an existing regular file.  This follows symbolic
-   links, so both :func:`islink` and :func:`isfile` can be true for the same path.
+   Return ``True`` if *path* is an :func:`existing <exists>` regular file.
+   This follows symbolic links, so both :func:`islink` and :func:`isfile` can
+   be true for the same path.
 
    .. versionchanged:: 3.6
       Accepts a :term:`path-like object`.
@@ -255,8 +256,9 @@ the :mod:`glob` module.)
 
 .. function:: isdir(path)
 
-   Return ``True`` if *path* is an existing directory.  This follows symbolic
-   links, so both :func:`islink` and :func:`isdir` can be true for the same path.
+   Return ``True`` if *path* is an :func:`existing <exists>` directory.  This
+   follows symbolic links, so both :func:`islink` and :func:`isdir` can be true
+   for the same path.
 
    .. versionchanged:: 3.6
       Accepts a :term:`path-like object`.
@@ -264,8 +266,9 @@ the :mod:`glob` module.)
 
 .. function:: islink(path)
 
-   Return ``True`` if *path* refers to a directory entry that is a symbolic link.
-   Always ``False`` if symbolic links are not supported by the Python runtime.
+   Return ``True`` if *path* refers to an :func:`existing <exists>` directory
+   entry that is a symbolic link.  Always ``False`` if symbolic links are not
+   supported by the Python runtime.
 
    .. versionchanged:: 3.6
       Accepts a :term:`path-like object`.