diff --git a/Lib/wsgiref/handlers.py b/Lib/wsgiref/handlers.py
index 173e34c..0af1c8f 100644
--- a/Lib/wsgiref/handlers.py
+++ b/Lib/wsgiref/handlers.py
@@ -160,7 +160,7 @@
 
         Subclasses can extend this to add other defaults.
         """
-        if not self.headers.has_key('Content-Length'):
+        if 'Content-Length' not in self.headers:
             self.set_content_length()
 
     def start_response(self, status, headers,exc_info=None):
@@ -195,11 +195,11 @@
         if self.origin_server:
             if self.client_is_modern():
                 self._write('HTTP/%s %s\r\n' % (self.http_version,self.status))
-                if not self.headers.has_key('Date'):
+                if 'Date' not in self.headers:
                     self._write(
                         'Date: %s\r\n' % format_date_time(time.time())
                     )
-                if self.server_software and not self.headers.has_key('Server'):
+                if self.server_software and 'Server' not in self.headers:
                     self._write('Server: %s\r\n' % self.server_software)
         else:
             self._write('Status: %s\r\n' % self.status)
diff --git a/Lib/wsgiref/validate.py b/Lib/wsgiref/validate.py
index 23ab9f8..43784f9 100644
--- a/Lib/wsgiref/validate.py
+++ b/Lib/wsgiref/validate.py
@@ -345,7 +345,7 @@
             "Invalid CONTENT_LENGTH: %r" % environ['CONTENT_LENGTH'])
 
     if not environ.get('SCRIPT_NAME'):
-        assert_(environ.has_key('PATH_INFO'),
+        assert_('PATH_INFO' in environ,
             "One of SCRIPT_NAME or PATH_INFO are required (PATH_INFO "
             "should at least be '/' if SCRIPT_NAME is empty)")
     assert_(environ.get('SCRIPT_NAME') != '/',