Simplify various spots where: str() is called on something

that already is a string or the existence of the str class
is checked or a check is done for str twice. These all stem
from the initial unicode->str replacement.

Lib/idlelib/PyParse.py

@@ -104,33 +104,28 @@ for ch in "\"'\\\n#":
 _tran = ''.join(_tran)
 del ch
 
-try:
-    UnicodeType = type(str(""))
-except NameError:
-    UnicodeType = None
-
 class Parser:
 
     def __init__(self, indentwidth, tabwidth):
         self.indentwidth = indentwidth
         self.tabwidth = tabwidth
 
-    def set_str(self, str):
-        assert len(str) == 0 or str[-1] == '\n'
-        if type(str) is UnicodeType:
+    def set_str(self, s):
+        assert len(s) == 0 or s[-1] == '\n'
+        if isinstance(s, str):
             # The parse functions have no idea what to do with Unicode, so
             # replace all Unicode characters with "x".  This is "safe"
             # so long as the only characters germane to parsing the structure
             # of Python are 7-bit ASCII.  It's *necessary* because Unicode
             # strings don't have a .translate() method that supports
             # deletechars.
-            uniphooey = str
+            uniphooey = s
             str = []
-            push = str.append
+            push = s.append
             for raw in map(ord, uniphooey):
                 push(raw < 127 and chr(raw) or "x")
-            str = "".join(str)
-        self.str = str
+            s = "".join(s)
+        self.str = s
         self.study_level = 0
 
     # Return index of a good place to begin parsing, as close to the