diff --git a/Lib/robotparser.py b/Lib/robotparser.py
index 48ea066..0a2ede1 100644
--- a/Lib/robotparser.py
+++ b/Lib/robotparser.py
@@ -65,7 +65,7 @@
             lines.append(line.strip())
             line = f.readline()
         self.errcode = opener.errcode
-        if self.errcode == 401 or self.errcode == 403:
+        if self.errcode in (401, 403):
             self.disallow_all = True
             _debug("disallow all")
         elif self.errcode >= 400:
@@ -168,10 +168,7 @@
 
 
     def __str__(self):
-        ret = ""
-        for entry in self.entries:
-            ret = ret + str(entry) + "\n"
-        return ret
+        return ''.join([str(entry) + "\n" for entry in self.entries])
 
 
 class RuleLine:
@@ -198,12 +195,12 @@
         self.rulelines = []
 
     def __str__(self):
-        ret = ""
+        ret = []
         for agent in self.useragents:
-            ret = ret + "User-agent: "+agent+"\n"
+            ret.extend(["User-agent: ", agent, "\n"])
         for line in self.rulelines:
-            ret = ret + str(line) + "\n"
-        return ret
+            ret.extend([str(line), "\n"])
+        return ''.join(ret)
 
     def applies_to(self, useragent):
         """check if this entry applies to the specified agent"""