gh-155358: Use named attributes with pwd and grp modules (#155362)

* Replace pwd[0] with pwd.pw_name
* Replace pwd[2] with pwd.pw_uid
* Replace grp[0] with grp.gr_name
* Replace grp[2] with grp.gr_gid
* Replace pwd[3] with pwd.pw_gid

Author: vstinner

Doc/library/os.rst

@@ -452,7 +452,7 @@ process and user.
    process.  For most purposes, it is more useful to use
    :func:`getpass.getuser` since the latter checks the environment variables
    :envvar:`LOGNAME` or :envvar:`USERNAME` to find out who the user is, and
-   falls back to ``pwd.getpwuid(os.getuid())[0]`` to get the login name of the
+   falls back to ``pwd.getpwuid(os.getuid()).pw_name`` to get the login name of the
    current real user id.
 
    .. availability:: Unix, Windows, not WASI.

Lib/getpass.py

@@ -428,7 +428,7 @@ def getuser():
 
     try:
         import pwd
-        return pwd.getpwuid(os.getuid())[0]
+        return pwd.getpwuid(os.getuid()).pw_name
     except (ImportError, KeyError) as e:
         raise OSError('No username set in the environment') from e
 

Lib/http/server.py

@@ -1013,7 +1013,7 @@ def nobody_uid():
     except ImportError:
         return -1
     try:
-        nobody = pwd.getpwnam('nobody')[2]
+        nobody = pwd.getpwnam('nobody').pw_uid
     except KeyError:
         nobody = 1 + max(x[2] for x in pwd.getpwall())
     return nobody

Lib/netrc.py

@@ -15,7 +15,7 @@ def _can_security_check():
 def _getpwuid(uid):
     try:
         import pwd
-        return pwd.getpwuid(uid)[0]
+        return pwd.getpwuid(uid).pw_name
     except (ImportError, LookupError):
         return f'uid {uid}'
 

Lib/shutil.py

@@ -983,7 +983,7 @@ def _get_gid(name):
     except KeyError:
         result = None
     if result is not None:
-        return result[2]
+        return result.gr_gid
     return None
 
 def _get_uid(name):
@@ -1001,7 +1001,7 @@ def _get_uid(name):
     except KeyError:
         result = None
     if result is not None:
-        return result[2]
+        return result.pw_uid
     return None
 
 def _make_tarball(base_name, base_dir, compress="gzip", verbose=0, dry_run=0,

Lib/tarfile.py

@@ -2282,14 +2282,14 @@ def gettarinfo(self, name=None, arcname=None, fileobj=None):
         if pwd:
             if tarinfo.uid not in self._unames:
                 try:
-                    self._unames[tarinfo.uid] = pwd.getpwuid(tarinfo.uid)[0]
+                    self._unames[tarinfo.uid] = pwd.getpwuid(tarinfo.uid).pw_name
                 except KeyError:
                     self._unames[tarinfo.uid] = ''
             tarinfo.uname = self._unames[tarinfo.uid]
         if grp:
             if tarinfo.gid not in self._gnames:
                 try:
-                    self._gnames[tarinfo.gid] = grp.getgrgid(tarinfo.gid)[0]
+                    self._gnames[tarinfo.gid] = grp.getgrgid(tarinfo.gid).gr_name
                 except KeyError:
                     self._gnames[tarinfo.gid] = ''
             tarinfo.gname = self._gnames[tarinfo.gid]
@@ -2837,12 +2837,12 @@ def chown(self, tarinfo, targetpath, numeric_owner):
             if not numeric_owner:
                 try:
                     if grp and tarinfo.gname:
-                        g = grp.getgrnam(tarinfo.gname)[2]
+                        g = grp.getgrnam(tarinfo.gname).gr_gid
                 except KeyError:
                     pass
                 try:
                     if pwd and tarinfo.uname:
-                        u = pwd.getpwnam(tarinfo.uname)[2]
+                        u = pwd.getpwnam(tarinfo.uname).pw_uid
                 except KeyError:
                     pass
             if g is None:

Lib/test/support/smtpd.py

@@ -862,7 +862,7 @@ def parseargs():
         except ImportError:
             print('Cannot import module "pwd"; try running with -n option.', file=sys.stderr)
             sys.exit(1)
-        nobody = pwd.getpwnam('nobody')[2]
+        nobody = pwd.getpwnam('nobody').pw_uid
         try:
             os.setuid(nobody)
         except PermissionError:

Lib/test/test_getpass.py

@@ -39,10 +39,13 @@ def test_username_falls_back_to_pwd(self, environ):
         expected_name = 'some_name'
         environ.get.return_value = None
         if pwd:
+            class User:
+                pass
             with mock.patch('os.getuid') as uid, \
                     mock.patch('pwd.getpwuid') as getpw:
                 uid.return_value = 42
-                getpw.return_value = [expected_name]
+                getpw.return_value = User()
+                getpw.return_value.pw_name = expected_name
                 self.assertEqual(expected_name,
                                  getpass.getuser())
                 getpw.assert_called_once_with(42)

Lib/test/test_os/test_posix.py

@@ -1322,8 +1322,8 @@ def _create_and_do_getcwd(dirname, current_path_length = 0):
     @unittest.skipUnless(hasattr(pwd, 'getpwuid'), "test needs pwd.getpwuid()")
     @unittest.skipUnless(hasattr(os, 'getuid'), "test needs os.getuid()")
     def test_getgrouplist(self):
-        user = pwd.getpwuid(os.getuid())[0]
-        group = pwd.getpwuid(os.getuid())[3]
+        user = pwd.getpwuid(os.getuid()).pw_name
+        group = pwd.getpwuid(os.getuid()).pw_gid
         self.assertIn(group, posix.getgrouplist(user, group))
 
 

Lib/test/test_pwd.py

@@ -50,7 +50,7 @@ def test_values_extended(self):
         # check whether the entry returned by getpwuid()
         # for each uid is among those from getpwall() for this uid
         for e in entries:
-            if not e[0] or e[0] == '+':
+            if not e.pw_name or e.pw_name == '+':
                 continue # skip NIS entries etc.
             self.assertIn(pwd.getpwnam(e.pw_name), entriesbyname[e.pw_name])
             self.assertIn(pwd.getpwuid(e.pw_uid), entriesbyuid[e.pw_uid])