#2650: Refactor re.escape to use enumerate().

Lib/re.py

@@ -223,8 +223,7 @@ def escape(pattern):
     if isinstance(pattern, str):
         alphanum = _alphanum_str
         s = list(pattern)
-        for i in range(len(pattern)):
-            c = pattern[i]
+        for i, c in enumerate(pattern):
             if c not in alphanum:
                 if c == "\000":
                     s[i] = "\\000"