gh-XXXXX: Fix pprint.isreadable() returning True for inf/nan

inf, -inf, nan are not valid Python literals so eval() fails on them.
isreadable() should return False for these values.

Author: stefanzetzsche

Lib/pprint.py

@@ -627,7 +627,10 @@ def _safe_repr(self, object, context, maxlevels, level):
         # Return triple (repr_string, isreadable, isrecursive).
         typ = type(object)
         if typ in _builtin_scalars:
-            return repr(object), True, False
+            rep = repr(object)
+            if typ is float and rep in ("inf", "-inf", "nan"):
+                return rep, False, False
+            return rep, True, False
 
         r = getattr(typ, "__repr__", None)
 

Lib/test/test_pprint.py

@@ -182,6 +182,14 @@ def test_basic(self):
             self.assertTrue(pp.isreadable(safe),
                             "expected isreadable for %r" % (safe,))
 
+    def test_isreadable_float_specials(self):
+        # inf, -inf, nan are not valid Python literals so isreadable should be False
+        for v in (float("inf"), float("-inf"), float("nan")):
+            self.assertFalse(pprint.isreadable(v),
+                             "expected not isreadable for %r" % (v,))
+            self.assertFalse(pprint.PrettyPrinter().isreadable(v),
+                             "expected not isreadable for %r" % (v,))
+
     def test_stdout_is_None(self):
         with contextlib.redirect_stdout(None):
             # smoke test - there is no output to check