ENH/CLN: add string and binary types compat object

Author: cpcloud

pandas/compat/__init__.py

@@ -185,6 +185,10 @@ def u(s):
     def u(s):
         return unicode(s, "unicode_escape")
 
+
+string_and_binary_types = string_types + (binary_type,)
+
+
 try:
     # callable reintroduced in later versions of Python
     callable = callable

pandas/core/common.py

@@ -1613,7 +1613,7 @@ def _is_sequence(x):
     try:
         iter(x)
         len(x)  # it has a length
-        return not isinstance(x, compat.string_types + (compat.binary_type,))
+        return not isinstance(x, compat.string_and_binary_types)
     except (TypeError, AttributeError):
         return False