As for the .upper() and .lower() methods, they are used in quite a bunch
of standard library modules :-/...

Lib/base64.py
Lib/BaseHTTPServer.py
Lib/bsddb/test/test_compare.py
Lib/bsddb/test/test_dbobj.py
Lib/CGIHTTPServer.py
Lib/cgi.py
Lib/compiler/ast.py
Lib/ConfigParser.py
Lib/cookielib.py
Lib/Cookie.py
Lib/csv.py
Lib/ctypes/test/test_byteswap.py
Lib/ctypes/util.py
Lib/decimal.py
Lib/distutils/command/bdist_rpm.py
Lib/distutils/command/bdist_wininst.py
Lib/distutils/command/register.py
Lib/distutils/msvc9compiler.py
Lib/distutils/msvccompiler.py
Lib/distutils/sysconfig.py
Lib/distutils/tests/test_dist.py
Lib/distutils/util.py
Lib/email/charset.py
Lib/email/encoders.py
Lib/email/header.py
Lib/email/__init__.py
Lib/email/message.py
Lib/email/_parseaddr.py
Lib/email/test/test_email.py
Lib/email/test/test_email_renamed.py
Lib/encodings/idna.py
Lib/encodings/punycode.py
Lib/formatter.py
Lib/ftplib.py
Lib/gettext.py
Lib/htmllib.py
Lib/HTMLParser.py
Lib/httplib.py
Lib/idlelib/configDialog.py
Lib/idlelib/EditorWindow.py
Lib/idlelib/IOBinding.py
Lib/idlelib/keybindingDialog.py
Lib/idlelib/PyShell.py
Lib/idlelib/SearchDialogBase.py
Lib/idlelib/tabbedpages.py
Lib/idlelib/TreeWidget.py
Lib/imaplib.py
Lib/inspect.py
Lib/lib-tk/turtle.py
Lib/locale.py
Lib/logging/handlers.py
Lib/logging/__init__.py
Lib/_LWPCookieJar.py
Lib/macpath.py
Lib/mailcap.py
Lib/markupbase.py
Lib/mhlib.py
Lib/mimetools.py
Lib/mimetypes.py
Lib/mimify.py
Lib/msilib/__init__.py
Lib/nntplib.py
Lib/ntpath.py
Lib/nturl2path.py
Lib/optparse.py
Lib/os2emxpath.py
Lib/os.py
Lib/pdb.py
Lib/plat-irix5/flp.py
Lib/plat-irix6/flp.py
Lib/plat-mac/buildtools.py
Lib/plat-mac/gensuitemodule.py
Lib/plat-riscos/riscospath.py
Lib/pyclbr.py
Lib/rfc822.py
Lib/robotparser.py
Lib/sgmllib.py
Lib/SimpleHTTPServer.py
Lib/smtpd.py
Lib/smtplib.py
Lib/socket.py
Lib/sqlite3/test/hooks.py
Lib/sre_constants.py
Lib/stringold.py
Lib/stringprep.py
Lib/string.py
Lib/_strptime.py
Lib/subprocess.py
Lib/test/regrtest.py
Lib/test/test_bigmem.py
Lib/test/test_codeccallbacks.py
Lib/test/test_codecs.py
Lib/test/test_cookielib.py
Lib/test/test_datetime.py
Lib/test/test_decimal.py
Lib/test/test_deque.py
Lib/test/test_descr.py
Lib/test/test_fileinput.py
Lib/test/test_grp.py
Lib/test/test_hmac.py
Lib/test/test_httplib.py
Lib/test/test_os.py
Lib/test/test_smtplib.py
Lib/test/test_sort.py
Lib/test/test_ssl.py
Lib/test/test_strop.py
Lib/test/test_strptime.py
Lib/test/test_support.py
Lib/test/test_ucn.py
Lib/test/test_unicodedata.py
Lib/test/test_urllib2.py
Lib/test/test_urllib.py
Lib/test/test_wsgiref.py
Lib/test/test_xmlrpc.py
Lib/urllib2.py
Lib/urllib.py
Lib/urlparse.py
Lib/UserString.py
Lib/uuid.py
Lib/warnings.py
Lib/webbrowser.py
Lib/wsgiref/handlers.py
Lib/wsgiref/headers.py
Lib/wsgiref/simple_server.py
Lib/wsgiref/util.py
Lib/wsgiref/validate.py
Lib/xml/dom/minidom.py
Lib/xml/dom/xmlbuilder.py
Lib/xmllib.py