Add various string conversion utilities

documentation/index.rst

@@ -452,6 +452,30 @@ string data in all Python versions.
    :meth:`py3:str.encode`
 
 
+.. function:: str_to_binary(s, encoding='utf-8', errors='strict')
+
+   Encodes s to from ``str`` to :data:`binary_type` in python 3 only. No-op in python 2.
+   *encoding*, *errors* are same as :meth:`py3.str.encode`
+
+
+.. function:: binary_to_str(s, encoding='utf-8', errors='strict')
+
+   Decodes s from :data:`binary_type` to ``str`` in python 3 only. No-op in python 2.
+   *encoding*, *errors* are same as :meth:`py3.str.encode`
+
+
+.. function:: str_to_text(s, encoding='utf-8', errors='strict')
+
+   Decodes s from ``str`` to :data:`text_type` in python 2 only. No-op in python 3.
+   *encoding*, *errors* are same as :meth:`py3.str.encode`
+
+
+.. function:: text_to_str(s, encoding='utf-8', errors='strict')
+
+   Encodes s from :data:`text_type` to ``str`` in python 2 only. No-op in python 3.
+   *encoding*, *errors* are same as :meth:`py3.str.encode`
+
+
 .. data:: StringIO
 
    This is a fake file object for textual data.  It's an alias for

six.py

@@ -908,6 +908,31 @@ def ensure_text(s, encoding='utf-8', errors='strict'):
         raise TypeError("not expecting type '%s'" % type(s))
 
 
+if PY3:
+    def binary_to_str(s, encoding='utf-8', errors='strict'):
+        return s.decode(encoding, errors)
+
+    def str_to_binary(s, encoding='utf-8', errors='strict'):
+        return s.encode(encoding, errors)
+
+    def text_to_str(s, encoding='utf-8', errors='strict'):
+        return s
+
+    def str_to_text(s, encoding='utf-8', errors='strict'):
+        return s
+else:
+    def binary_to_str(s, encoding='utf-8', errors='strict'):
+        return s
+
+    def str_to_binary(s, encoding='utf-8', errors='strict'):
+        return s
+
+    def text_to_str(s, encoding='utf-8', errors='strict'):
+        return s.encode(encoding, errors)
+
+    def str_to_text(s, encoding='utf-8', errors='strict'):
+        return s.decode(encoding, errors)
+
 
 def python_2_unicode_compatible(klass):
     """

test_six.py

@@ -954,12 +954,23 @@ def __bytes__(self):
     assert getattr(six.moves.builtins, 'bytes', str)(my_test) == six.b("hello")
 
 
-class EnsureTests:
+# grinning face emoji
+UNICODE_EMOJI = six.u("\U0001F600")
+BINARY_EMOJI = b"\xf0\x9f\x98\x80"
+if six.PY2:
+    STR_EMOJI = BINARY_EMOJI
+else:
+    STR_EMOJI = UNICODE_EMOJI
+
 
-    # grinning face emoji
-    UNICODE_EMOJI = six.u("\U0001F600")
-    BINARY_EMOJI = b"\xf0\x9f\x98\x80"
+def test_str_conversions():
+    assert six.binary_to_str(BINARY_EMOJI) == STR_EMOJI
+    assert six.str_to_binary(STR_EMOJI) == BINARY_EMOJI
+    assert six.text_to_str(UNICODE_EMOJI) == STR_EMOJI
+    assert six.str_to_text(STR_EMOJI) == UNICODE_EMOJI
 
+
+class EnsureTests:
     def test_ensure_binary_raise_type_error(self):
         with py.test.raises(TypeError):
             six.ensure_str(8)