diff --git a/src/if_py_both.h b/src/if_py_both.h
index f78eccb..72ec8b0 100644
--- a/src/if_py_both.h
+++ b/src/if_py_both.h
@@ -65,10 +65,10 @@ static struct PyMethodDef OutputMethods[] = {
 OutputWrite(PyObject *self, PyObject *args)
 {
     int len;
-    char *str;
+    char *str = NULL;
     int error = ((OutputObject *)(self))->error;
 
-    if (!PyArg_ParseTuple(args, "s#", &str, &len))
+    if (!PyArg_ParseTuple(args, "es#", p_enc, &str, &len))
 	return NULL;
 
     Py_BEGIN_ALLOW_THREADS
@@ -76,6 +76,7 @@ OutputWrite(PyObject *self, PyObject *args)
     writer((writefn)(error ? emsg : msg), (char_u *)str, len);
     Python_Release_Vim();
     Py_END_ALLOW_THREADS
+    PyMem_Free(str);
 
     Py_INCREF(Py_None);
     return Py_None;
@@ -104,10 +105,10 @@ OutputWritelines(PyObject *self, PyObject *args)
     for (i = 0; i < n; ++i)
     {
 	PyObject *line = PyList_GetItem(list, i);
-	char *str;
+	char *str = NULL;
 	PyInt len;
 
-	if (!PyArg_Parse(line, "s#", &str, &len)) {
+	if (!PyArg_Parse(line, "es#", p_enc, &str, &len)) {
 	    PyErr_SetString(PyExc_TypeError, _("writelines() requires list of strings"));
 	    Py_DECREF(list);
 	    return NULL;
@@ -118,6 +119,7 @@ OutputWritelines(PyObject *self, PyObject *args)
 	writer((writefn)(error ? emsg : msg), (char_u *)str, len);
 	Python_Release_Vim();
 	Py_END_ALLOW_THREADS
+	PyMem_Free(str);
     }
 
     Py_DECREF(list);
@@ -681,6 +683,7 @@ StringToLine(PyObject *obj)
 {
     const char *str;
     char *save;
+    PyObject *bytes;
     PyInt len;
     PyInt i;
     char *p;
@@ -691,8 +694,9 @@ StringToLine(PyObject *obj)
 	return NULL;
     }
 
-    str = PyString_AsString(obj);
-    len = PyString_Size(obj);
+    bytes = PyString_AsBytes(obj);
+    str = PyString_AsString(bytes);
+    len = PyString_Size(bytes);
 
     /*
      * Error checking: String must not contain newlines, as we
@@ -731,6 +735,7 @@ StringToLine(PyObject *obj)
     }
 
     save[i] = '\0';
+    PyString_FreeBytes(bytes);
 
     return save;
 }
@@ -908,6 +913,193 @@ SetBufferLine(buf_T *buf, PyInt n, PyObject *line, PyInt *len_change)
     }
 }
 
+/* Replace a range of lines in the specified buffer. The line numbers are in
+ * Vim format (1-based). The range is from lo up to, but not including, hi.
+ * The replacement lines are given as a Python list of string objects. The
+ * list is checked for validity and correct format. Errors are returned as a
+ * value of FAIL.  The return value is OK on success.
+ * If OK is returned and len_change is not NULL, *len_change
+ * is set to the change in the buffer length.
+ */
+    static int
+SetBufferLineList(buf_T *buf, PyInt lo, PyInt hi, PyObject *list, PyInt *len_change)
+{
+    /* First of all, we check the thpe of the supplied Python object.
+     * There are three cases:
+     *	  1. NULL, or None - this is a deletion.
+     *	  2. A list	   - this is a replacement.
+     *	  3. Anything else - this is an error.
+     */
+    if (list == Py_None || list == NULL)
+    {
+	PyInt	i;
+	PyInt	n = (int)(hi - lo);
+	buf_T	*savebuf = curbuf;
+
+	PyErr_Clear();
+	curbuf = buf;
+
+	if (u_savedel((linenr_T)lo, (long)n) == FAIL)
+	    PyErr_SetVim(_("cannot save undo information"));
+	else
+	{
+	    for (i = 0; i < n; ++i)
+	    {
+		if (ml_delete((linenr_T)lo, FALSE) == FAIL)
+		{
+		    PyErr_SetVim(_("cannot delete line"));
+		    break;
+		}
+	    }
+	    if (buf == curwin->w_buffer)
+		py_fix_cursor((linenr_T)lo, (linenr_T)hi, (linenr_T)-n);
+	    deleted_lines_mark((linenr_T)lo, (long)i);
+	}
+
+	curbuf = savebuf;
+
+	if (PyErr_Occurred() || VimErrorCheck())
+	    return FAIL;
+
+	if (len_change)
+	    *len_change = -n;
+
+	return OK;
+    }
+    else if (PyList_Check(list))
+    {
+	PyInt	i;
+	PyInt	new_len = PyList_Size(list);
+	PyInt	old_len = hi - lo;
+	PyInt	extra = 0;	/* lines added to text, can be negative */
+	char	**array;
+	buf_T	*savebuf;
+
+	if (new_len == 0)	/* avoid allocating zero bytes */
+	    array = NULL;
+	else
+	{
+	    array = (char **)alloc((unsigned)(new_len * sizeof(char *)));
+	    if (array == NULL)
+	    {
+		PyErr_NoMemory();
+		return FAIL;
+	    }
+	}
+
+	for (i = 0; i < new_len; ++i)
+	{
+	    PyObject *line = PyList_GetItem(list, i);
+
+	    array[i] = StringToLine(line);
+	    if (array[i] == NULL)
+	    {
+		while (i)
+		    vim_free(array[--i]);
+		vim_free(array);
+		return FAIL;
+	    }
+	}
+
+	savebuf = curbuf;
+
+	PyErr_Clear();
+	curbuf = buf;
+
+	if (u_save((linenr_T)(lo-1), (linenr_T)hi) == FAIL)
+	    PyErr_SetVim(_("cannot save undo information"));
+
+	/* If the size of the range is reducing (ie, new_len < old_len) we
+	 * need to delete some old_len. We do this at the start, by
+	 * repeatedly deleting line "lo".
+	 */
+	if (!PyErr_Occurred())
+	{
+	    for (i = 0; i < old_len - new_len; ++i)
+		if (ml_delete((linenr_T)lo, FALSE) == FAIL)
+		{
+		    PyErr_SetVim(_("cannot delete line"));
+		    break;
+		}
+	    extra -= i;
+	}
+
+	/* For as long as possible, replace the existing old_len with the
+	 * new old_len. This is a more efficient operation, as it requires
+	 * less memory allocation and freeing.
+	 */
+	if (!PyErr_Occurred())
+	{
+	    for (i = 0; i < old_len && i < new_len; ++i)
+		if (ml_replace((linenr_T)(lo+i), (char_u *)array[i], FALSE)
+								      == FAIL)
+		{
+		    PyErr_SetVim(_("cannot replace line"));
+		    break;
+		}
+	}
+	else
+	    i = 0;
+
+	/* Now we may need to insert the remaining new old_len. If we do, we
+	 * must free the strings as we finish with them (we can't pass the
+	 * responsibility to vim in this case).
+	 */
+	if (!PyErr_Occurred())
+	{
+	    while (i < new_len)
+	    {
+		if (ml_append((linenr_T)(lo + i - 1),
+					(char_u *)array[i], 0, FALSE) == FAIL)
+		{
+		    PyErr_SetVim(_("cannot insert line"));
+		    break;
+		}
+		vim_free(array[i]);
+		++i;
+		++extra;
+	    }
+	}
+
+	/* Free any left-over old_len, as a result of an error */
+	while (i < new_len)
+	{
+	    vim_free(array[i]);
+	    ++i;
+	}
+
+	/* Free the array of old_len. All of its contents have now
+	 * been dealt with (either freed, or the responsibility passed
+	 * to vim.
+	 */
+	vim_free(array);
+
+	/* Adjust marks. Invalidate any which lie in the
+	 * changed range, and move any in the remainder of the buffer.
+	 */
+	mark_adjust((linenr_T)lo, (linenr_T)(hi - 1),
+						  (long)MAXLNUM, (long)extra);
+	changed_lines((linenr_T)lo, 0, (linenr_T)hi, (long)extra);
+
+	if (buf == curwin->w_buffer)
+	    py_fix_cursor((linenr_T)lo, (linenr_T)hi, (linenr_T)extra);
+
+	curbuf = savebuf;
+
+	if (PyErr_Occurred() || VimErrorCheck())
+	    return FAIL;
+
+	if (len_change)
+	    *len_change = new_len - old_len;
+
+	return OK;
+    }
+    else
+    {
+	PyErr_BadArgument();
+	return FAIL;
+    }
+}
 
 /* Insert a number of lines into the specified buffer after the specifed line.
  * The line number is in Vim format (1-based). The lines to be inserted are
@@ -1113,6 +1305,40 @@ RBAsItem(BufferObject *self, PyInt n, PyObject *val, PyInt start, PyInt end, PyI
     return 0;
 }
 
+    static PyInt
+RBAsSlice(BufferObject *self, PyInt lo, PyInt hi, PyObject *val, PyInt start, PyInt end, PyInt *new_end)
+{
+    PyInt size;
+    PyInt len_change;
+
+    /* Self must be a valid buffer */
+    if (CheckBuffer(self))
+	return -1;
+
+    /* Sort out the slice range */
+    size = end - start + 1;
+
+    if (lo < 0)
+	lo = 0;
+    else if (lo > size)
+	lo = size;
+    if (hi < 0)
+	hi = 0;
+    if (hi < lo)
+	hi = lo;
+    else if (hi > size)
+	hi = size;
+
+    if (SetBufferLineList(self->buf, lo + start, hi + start,
+						    val, &len_change) == FAIL)
+	return -1;
+
+    if (new_end)
+	*new_end = end + len_change;
+
+    return 0;
+}
+
 
     static PyObject *
 RBAppend(BufferObject *self, PyObject *args, PyInt start, PyInt end, PyInt *new_end)
diff --git a/src/if_python.c b/src/if_python.c
index d35e9ab..dd9d6da 100644
--- a/src/if_python.c
+++ b/src/if_python.c
@@ -56,6 +56,9 @@
 
 static void init_structs(void);
 
+#define PyString_AsBytes(obj) (obj)
+#define PyString_FreeBytes(obj) (bytes)
+
 #if !defined(FEAT_PYTHON) && defined(PROTO)
 /* Use this to be able to generate prototypes without python being used. */
 # define PyObject Py_ssize_t
@@ -129,6 +132,7 @@ struct PyMethodDef { Py_ssize_t a; };
  */
 # define PyArg_Parse dll_PyArg_Parse
 # define PyArg_ParseTuple dll_PyArg_ParseTuple
+# define PyMem_Free dll_PyMem_Free
 # define PyDict_SetItemString dll_PyDict_SetItemString
 # define PyErr_BadArgument dll_PyErr_BadArgument
 # define PyErr_Clear dll_PyErr_Clear
@@ -189,6 +193,7 @@ struct PyMethodDef { Py_ssize_t a; };
  */
 static int(*dll_PyArg_Parse)(PyObject *, char *, ...);
 static int(*dll_PyArg_ParseTuple)(PyObject *, char *, ...);
+static int(*dll_PyMem_Free)(void *);
 static int(*dll_PyDict_SetItemString)(PyObject *dp, char *key, PyObject *item);
 static int(*dll_PyErr_BadArgument)(void);
 static void(*dll_PyErr_Clear)(void);
@@ -271,6 +276,7 @@ static struct
 {
     {"PyArg_Parse", (PYTHON_PROC*)&dll_PyArg_Parse},
     {"PyArg_ParseTuple", (PYTHON_PROC*)&dll_PyArg_ParseTuple},
+    {"PyMem_Free", (PYTHON_PROC*)&dll_PyMem_Free},
     {"PyDict_SetItemString", (PYTHON_PROC*)&dll_PyDict_SetItemString},
     {"PyErr_BadArgument", (PYTHON_PROC*)&dll_PyErr_BadArgument},
     {"PyErr_Clear", (PYTHON_PROC*)&dll_PyErr_Clear},
@@ -833,44 +839,6 @@ static PyInt RangeAssSlice(PyObject *, PyInt, PyInt, PyObject *);
 static PyObject *CurrentGetattr(PyObject *, char *);
 static int CurrentSetattr(PyObject *, char *, PyObject *);
 
-/* Common routines for buffers and line ranges
- * -------------------------------------------
- */
-
-    static PyInt
-RBAssSlice(BufferObject *self, PyInt lo, PyInt hi, PyObject *val, PyInt start, PyInt end, PyInt *new_end)
-{
-    PyInt size;
-    PyInt len_change;
-
-    /* Self must be a valid buffer */
-    if (CheckBuffer(self))
-	return -1;
-
-    /* Sort out the slice range */
-    size = end - start + 1;
-
-    if (lo < 0)
-	lo = 0;
-    else if (lo > size)
-	lo = size;
-    if (hi < 0)
-	hi = 0;
-    if (hi < lo)
-	hi = lo;
-    else if (hi > size)
-	hi = size;
-
-    if (SetBufferLineList(self->buf, lo + start, hi + start,
-						    val, &len_change) == FAIL)
-	return -1;
-
-    if (new_end)
-	*new_end = end + len_change;
-
-    return 0;
-}
-
 static PySequenceMethods BufferAsSeq = {
     (PyInquiry)		BufferLength,	    /* sq_length,    len(x)   */
     (binaryfunc)	0, /* BufferConcat, */	     /* sq_concat,    x+y      */
@@ -1038,7 +1006,7 @@ BufferAssItem(PyObject *self, PyInt n, PyObject *val)
     static PyInt
 BufferAssSlice(PyObject *self, PyInt lo, PyInt hi, PyObject *val)
 {
-    return RBAssSlice((BufferObject *)(self), lo, hi, val, 1,
+    return RBAsSlice((BufferObject *)(self), lo, hi, val, 1,
 		      (PyInt)((BufferObject *)(self))->buf->b_ml.ml_line_count,
 		      NULL);
 }
@@ -1088,7 +1056,7 @@ RangeAssItem(PyObject *self, PyInt n, PyObject *val)
     static PyInt
 RangeAssSlice(PyObject *self, PyInt lo, PyInt hi, PyObject *val)
 {
-    return RBAssSlice(((RangeObject *)(self))->buf, lo, hi, val,
+    return RBAsSlice(((RangeObject *)(self))->buf, lo, hi, val,
 		      ((RangeObject *)(self))->start,
 		      ((RangeObject *)(self))->end,
 		      &((RangeObject *)(self))->end);
@@ -1435,194 +1403,6 @@ PythonMod_Init(void)
  * 4. Utility functions for handling the interface between Vim and Python.
  */
 
-/* Replace a range of lines in the specified buffer. The line numbers are in
- * Vim format (1-based). The range is from lo up to, but not including, hi.
- * The replacement lines are given as a Python list of string objects. The
- * list is checked for validity and correct format. Errors are returned as a
- * value of FAIL.  The return value is OK on success.
- * If OK is returned and len_change is not NULL, *len_change
- * is set to the change in the buffer length.
- */
-    static int
-SetBufferLineList(buf_T *buf, PyInt lo, PyInt hi, PyObject *list, PyInt *len_change)
-{
-    /* First of all, we check the thpe of the supplied Python object.
-     * There are three cases:
-     *	  1. NULL, or None - this is a deletion.
-     *	  2. A list	   - this is a replacement.
-     *	  3. Anything else - this is an error.
-     */
-    if (list == Py_None || list == NULL)
-    {
-	PyInt	i;
-	PyInt	n = (int)(hi - lo);
-	buf_T	*savebuf = curbuf;
-
-	PyErr_Clear();
-	curbuf = buf;
-
-	if (u_savedel((linenr_T)lo, (long)n) == FAIL)
-	    PyErr_SetVim(_("cannot save undo information"));
-	else
-	{
-	    for (i = 0; i < n; ++i)
-	    {
-		if (ml_delete((linenr_T)lo, FALSE) == FAIL)
-		{
-		    PyErr_SetVim(_("cannot delete line"));
-		    break;
-		}
-	    }
-	    if (buf == curwin->w_buffer)
-		py_fix_cursor((linenr_T)lo, (linenr_T)hi, (linenr_T)-n);
-	    deleted_lines_mark((linenr_T)lo, (long)i);
-	}
-
-	curbuf = savebuf;
-
-	if (PyErr_Occurred() || VimErrorCheck())
-	    return FAIL;
-
-	if (len_change)
-	    *len_change = -n;
-
-	return OK;
-    }
-    else if (PyList_Check(list))
-    {
-	PyInt	i;
-	PyInt	new_len = PyList_Size(list);
-	PyInt	old_len = hi - lo;
-	PyInt	extra = 0;	/* lines added to text, can be negative */
-	char	**array;
-	buf_T	*savebuf;
-
-	if (new_len == 0)	/* avoid allocating zero bytes */
-	    array = NULL;
-	else
-	{
-	    array = (char **)alloc((unsigned)(new_len * sizeof(char *)));
-	    if (array == NULL)
-	    {
-		PyErr_NoMemory();
-		return FAIL;
-	    }
-	}
-
-	for (i = 0; i < new_len; ++i)
-	{
-	    PyObject *line = PyList_GetItem(list, i);
-
-	    array[i] = StringToLine(line);
-	    if (array[i] == NULL)
-	    {
-		while (i)
-		    vim_free(array[--i]);
-		vim_free(array);
-		return FAIL;
-	    }
-	}
-
-	savebuf = curbuf;
-
-	PyErr_Clear();
-	curbuf = buf;
-
-	if (u_save((linenr_T)(lo-1), (linenr_T)hi) == FAIL)
-	    PyErr_SetVim(_("cannot save undo information"));
-
-	/* If the size of the range is reducing (ie, new_len < old_len) we
-	 * need to delete some old_len. We do this at the start, by
-	 * repeatedly deleting line "lo".
-	 */
-	if (!PyErr_Occurred())
-	{
-	    for (i = 0; i < old_len - new_len; ++i)
-		if (ml_delete((linenr_T)lo, FALSE) == FAIL)
-		{
-		    PyErr_SetVim(_("cannot delete line"));
-		    break;
-		}
-	    extra -= i;
-	}
-
-	/* For as long as possible, replace the existing old_len with the
-	 * new old_len. This is a more efficient operation, as it requires
-	 * less memory allocation and freeing.
-	 */
-	if (!PyErr_Occurred())
-	{
-	    for (i = 0; i < old_len && i < new_len; ++i)
-		if (ml_replace((linenr_T)(lo+i), (char_u *)array[i], FALSE)
-								      == FAIL)
-		{
-		    PyErr_SetVim(_("cannot replace line"));
-		    break;
-		}
-	}
-	else
-	    i = 0;
-
-	/* Now we may need to insert the remaining new old_len. If we do, we
-	 * must free the strings as we finish with them (we can't pass the
-	 * responsibility to vim in this case).
-	 */
-	if (!PyErr_Occurred())
-	{
-	    while (i < new_len)
-	    {
-		if (ml_append((linenr_T)(lo + i - 1),
-					(char_u *)array[i], 0, FALSE) == FAIL)
-		{
-		    PyErr_SetVim(_("cannot insert line"));
-		    break;
-		}
-		vim_free(array[i]);
-		++i;
-		++extra;
-	    }
-	}
-
-	/* Free any left-over old_len, as a result of an error */
-	while (i < new_len)
-	{
-	    vim_free(array[i]);
-	    ++i;
-	}
-
-	/* Free the array of old_len. All of its contents have now
-	 * been dealt with (either freed, or the responsibility passed
-	 * to vim.
-	 */
-	vim_free(array);
-
-	/* Adjust marks. Invalidate any which lie in the
-	 * changed range, and move any in the remainder of the buffer.
-	 */
-	mark_adjust((linenr_T)lo, (linenr_T)(hi - 1),
-						  (long)MAXLNUM, (long)extra);
-	changed_lines((linenr_T)lo, 0, (linenr_T)hi, (long)extra);
-
-	if (buf == curwin->w_buffer)
-	    py_fix_cursor((linenr_T)lo, (linenr_T)hi, (linenr_T)extra);
-
-	curbuf = savebuf;
-
-	if (PyErr_Occurred() || VimErrorCheck())
-	    return FAIL;
-
-	if (len_change)
-	    *len_change = new_len - old_len;
-
-	return OK;
-    }
-    else
-    {
-	PyErr_BadArgument();
-	return FAIL;
-    }
-}
-
 /* Convert a Vim line into a Python string.
  * All internal newlines are replaced by null characters.
  *
diff --git a/src/if_python3.c b/src/if_python3.c
index b253796..800ec83 100644
--- a/src/if_python3.c
+++ b/src/if_python3.c
@@ -70,8 +70,10 @@ static void init_structs(void);
 
 #define PyInt Py_ssize_t
 #define PyString_Check(obj) PyUnicode_Check(obj)
-#define PyString_AsString(obj) _PyUnicode_AsString(obj)
-#define PyString_Size(obj) PyUnicode_GET_SIZE(obj)
+#define PyString_AsBytes(obj) PyUnicode_AsEncodedString(obj, p_enc, NULL);
+#define PyString_FreeBytes(obj) Py_XDECREF(bytes)
+#define PyString_AsString(obj) PyBytes_AsString(obj)
+#define PyString_Size(obj) PyBytes_GET_SIZE(bytes)
 #define PyString_FromString(repr) PyUnicode_FromString(repr)
 
 #if defined(DYNAMIC_PYTHON3) || defined(PROTO)
@@ -99,6 +101,7 @@ static void init_structs(void);
 # define PyArg_Parse py3_PyArg_Parse
 # undef PyArg_ParseTuple
 # define PyArg_ParseTuple py3_PyArg_ParseTuple
+# define PyMem_Free py3_PyMem_Free
 # define PyDict_SetItemString py3_PyDict_SetItemString
 # define PyErr_BadArgument py3_PyErr_BadArgument
 # define PyErr_Clear py3_PyErr_Clear
@@ -140,8 +143,13 @@ static void init_structs(void);
 # define PyModule_AddObject py3_PyModule_AddObject
 # define PyImport_AppendInittab py3_PyImport_AppendInittab
 # define _PyUnicode_AsString py3__PyUnicode_AsString
+# undef PyUnicode_AsEncodedString
+# define PyUnicode_AsEncodedString py3_PyUnicode_AsEncodedString
+# undef PyBytes_AsString
+# define PyBytes_AsString py3_PyBytes_AsString
 # define PyObject_GenericGetAttr py3_PyObject_GenericGetAttr
 # define PySlice_Type (*py3_PySlice_Type)
+# define PyErr_NewException py3_PyErr_NewException
 # ifdef Py_DEBUG
 #  define _Py_NegativeRefcount py3__Py_NegativeRefcount
 #  define _Py_RefTotal (*py3__Py_RefTotal)
@@ -157,8 +165,8 @@ static void init_structs(void);
 # define PyModule_Create2 py3_PyModule_Create2
 # undef PyUnicode_FromString
 # define PyUnicode_FromString py3_PyUnicode_FromString
-# undef PyUnicode_FromStringAndSize
-# define PyUnicode_FromStringAndSize py3_PyUnicode_FromStringAndSize
+# undef PyUnicode_Decode
+# define PyUnicode_Decode py3_PyUnicode_Decode
 
 # ifdef Py_DEBUG
 #  undef PyObject_NEW
@@ -199,7 +207,8 @@ static PyObject* (*py3_Py_BuildValue)(char *, ...);
 static int (*py3_PyType_Ready)(PyTypeObject *type);
 static int (*py3_PyDict_SetItemString)(PyObject *dp, char *key, PyObject *item);
 static PyObject* (*py3_PyUnicode_FromString)(const char *u);
-static PyObject* (*py3_PyUnicode_FromStringAndSize)(const char *u, Py_ssize_t size);
+static PyObject* (*py3_PyUnicode_Decode)(const char *u, Py_ssize_t size,
+	const char *encoding, const char *errors);
 static long (*py3_PyLong_AsLong)(PyObject *);
 static void (*py3_PyErr_SetNone)(PyObject *);
 static void (*py3_PyEval_InitThreads)(void);
@@ -207,6 +216,7 @@ static void(*py3_PyEval_RestoreThread)(PyThreadState *);
 static PyThreadState*(*py3_PyEval_SaveThread)(void);
 static int (*py3_PyArg_Parse)(PyObject *, char *, ...);
 static int (*py3_PyArg_ParseTuple)(PyObject *, char *, ...);
+static int (*py3_PyMem_Free)(void *);
 static int (*py3_Py_IsInitialized)(void);
 static void (*py3_PyErr_Clear)(void);
 static PyObject*(*py3__PyObject_Init)(PyObject *, PyTypeObject *);
@@ -214,11 +224,14 @@ static PyObject* py3__Py_NoneStruct;
 static int (*py3_PyModule_AddObject)(PyObject *m, const char *name, PyObject *o);
 static int (*py3_PyImport_AppendInittab)(const char *name, PyObject* (*initfunc)(void));
 static char* (*py3__PyUnicode_AsString)(PyObject *unicode);
+static PyObject* (*py3_PyUnicode_AsEncodedString)(PyObject *unicode, const char* encoding, const char* errors);
+static char* (*py3_PyBytes_AsString)(PyObject *bytes);
 static PyObject* (*py3_PyObject_GenericGetAttr)(PyObject *obj, PyObject *name);
 static PyObject* (*py3_PyModule_Create2)(struct PyModuleDef* module, int module_api_version);
 static PyObject* (*py3_PyType_GenericAlloc)(PyTypeObject *type, Py_ssize_t nitems);
 static PyObject* (*py3_PyType_GenericNew)(PyTypeObject *type, PyObject *args, PyObject *kwds);
 static PyTypeObject* py3_PySlice_Type;
+static PyObject* (*py3_PyErr_NewException)(char *name, PyObject *base, PyObject *dict);
 # ifdef Py_DEBUG
     static void (*py3__Py_NegativeRefcount)(const char *fname, int lineno, PyObject *op);
     static Py_ssize_t* py3__Py_RefTotal;
@@ -259,6 +272,7 @@ static struct
     {"Py_SetPythonHome", (PYTHON_PROC*)&py3_Py_SetPythonHome},
     {"Py_Initialize", (PYTHON_PROC*)&py3_Py_Initialize},
     {"PyArg_ParseTuple", (PYTHON_PROC*)&py3_PyArg_ParseTuple},
+    {"PyMem_Free", (PYTHON_PROC*)&py3_PyMem_Free},
     {"PyList_New", (PYTHON_PROC*)&py3_PyList_New},
     {"PyGILState_Ensure", (PYTHON_PROC*)&py3_PyGILState_Ensure},
     {"PyGILState_Release", (PYTHON_PROC*)&py3_PyGILState_Release},
@@ -289,7 +303,6 @@ static struct
     {"PyEval_RestoreThread", (PYTHON_PROC*)&py3_PyEval_RestoreThread},
     {"PyEval_SaveThread", (PYTHON_PROC*)&py3_PyEval_SaveThread},
     {"PyArg_Parse", (PYTHON_PROC*)&py3_PyArg_Parse},
-    {"PyArg_ParseTuple", (PYTHON_PROC*)&py3_PyArg_ParseTuple},
     {"Py_IsInitialized", (PYTHON_PROC*)&py3_Py_IsInitialized},
     {"_Py_NoneStruct", (PYTHON_PROC*)&py3__Py_NoneStruct},
     {"PyErr_Clear", (PYTHON_PROC*)&py3_PyErr_Clear},
@@ -297,11 +310,13 @@ static struct
     {"PyModule_AddObject", (PYTHON_PROC*)&py3_PyModule_AddObject},
     {"PyImport_AppendInittab", (PYTHON_PROC*)&py3_PyImport_AppendInittab},
     {"_PyUnicode_AsString", (PYTHON_PROC*)&py3__PyUnicode_AsString},
+    {"PyBytes_AsString", (PYTHON_PROC*)&py3_PyBytes_AsString},
     {"PyObject_GenericGetAttr", (PYTHON_PROC*)&py3_PyObject_GenericGetAttr},
     {"PyModule_Create2", (PYTHON_PROC*)&py3_PyModule_Create2},
     {"PyType_GenericAlloc", (PYTHON_PROC*)&py3_PyType_GenericAlloc},
     {"PyType_GenericNew", (PYTHON_PROC*)&py3_PyType_GenericNew},
     {"PySlice_Type", (PYTHON_PROC*)&py3_PySlice_Type},
+    {"PyErr_NewException", (PYTHON_PROC*)&py3_PyErr_NewException},
 # ifdef Py_DEBUG
     {"_Py_NegativeRefcount", (PYTHON_PROC*)&py3__Py_NegativeRefcount},
     {"_Py_RefTotal", (PYTHON_PROC*)&py3__Py_RefTotal},
@@ -337,7 +352,7 @@ end_dynamic_python3(void)
 py3_runtime_link_init(char *libname, int verbose)
 {
     int i;
-    void *ucs_from_string, *ucs_from_string_and_size;
+    void *ucs_from_string, *ucs_decode, *ucs_as_encoded_string;
 
 # if !(defined(PY_NO_RTLD_GLOBAL) && defined(PY3_NO_RTLD_GLOBAL)) && defined(UNIX) && defined(FEAT_PYTHON)
     /* Can't have Python and Python3 loaded at the same time.
@@ -377,19 +392,24 @@ py3_runtime_link_init(char *libname, int verbose)
     /* Load unicode functions separately as only the ucs2 or the ucs4 functions
      * will be present in the library. */
     ucs_from_string = symbol_from_dll(hinstPy3, "PyUnicodeUCS2_FromString");
-    ucs_from_string_and_size = symbol_from_dll(hinstPy3,
-	    "PyUnicodeUCS2_FromStringAndSize");
-    if (!ucs_from_string || !ucs_from_string_and_size)
+    ucs_decode = symbol_from_dll(hinstPy3,
+	    "PyUnicodeUCS2_Decode");
+    ucs_as_encoded_string = symbol_from_dll(hinstPy3,
+	    "PyUnicodeUCS2_AsEncodedString");
+    if (!ucs_from_string || !ucs_decode || !ucs_as_encoded_string)
     {
 	ucs_from_string = symbol_from_dll(hinstPy3,
 		"PyUnicodeUCS4_FromString");
-	ucs_from_string_and_size = symbol_from_dll(hinstPy3,
-		"PyUnicodeUCS4_FromStringAndSize");
+	ucs_decode = symbol_from_dll(hinstPy3,
+		"PyUnicodeUCS4_Decode");
+	ucs_as_encoded_string = symbol_from_dll(hinstPy3,
+		"PyUnicodeUCS4_AsEncodedString");
     }
-    if (ucs_from_string && ucs_from_string_and_size)
+    if (ucs_from_string && ucs_decode && ucs_as_encoded_string)
     {
 	py3_PyUnicode_FromString = ucs_from_string;
-	py3_PyUnicode_FromStringAndSize = ucs_from_string_and_size;
+	py3_PyUnicode_Decode = ucs_decode;
+	py3_PyUnicode_AsEncodedString = ucs_as_encoded_string;
     }
     else
     {
@@ -568,8 +591,11 @@ Python3_Init(void)
 	/* Remove the element from sys.path that was added because of our
 	 * argv[0] value in Py3Init_vim().  Previously we used an empty
 	 * string, but dependinding on the OS we then get an empty entry or
-	 * the current directory in sys.path. */
-	PyRun_SimpleString("import sys; sys.path = list(filter(lambda x: x != '/must>not&exist', sys.path))");
+	 * the current directory in sys.path.
+	 * Only after vim has been imported, the element does exist in
+	 * sys.path.
+	 */
+	PyRun_SimpleString("import vim; import sys; sys.path = list(filter(lambda x: not x.endswith('must>not&exist'), sys.path))");
 
 	// lock is created and acquired in PyEval_InitThreads() and thread
 	// state is created in Py_Initialize()
@@ -606,6 +632,8 @@ DoPy3Command(exarg_T *eap, const char *cmd)
 #if defined(HAVE_LOCALE_H) || defined(X_LOCALE)
     char		*saved_locale;
 #endif
+    PyObject		*cmdstr;
+    PyObject		*cmdbytes;
 
 #if defined(MACOS) && !defined(MACOS_X_UNIX)
     GetPort(&oldPort);
@@ -635,7 +663,13 @@ DoPy3Command(exarg_T *eap, const char *cmd)
 
     pygilstate = PyGILState_Ensure();
 
-    PyRun_SimpleString((char *)(cmd));
+    /* PyRun_SimpleString expects a UTF-8 string. Wrong encoding may cause
+     * SyntaxError (unicode error). */
+    cmdstr = PyUnicode_Decode(cmd, strlen(cmd), p_enc, NULL);
+    cmdbytes = PyUnicode_AsEncodedString(cmdstr, "utf-8", NULL);
+    Py_XDECREF(cmdstr);
+    PyRun_SimpleString(PyBytes_AsString(cmdbytes));
+    Py_XDECREF(cmdbytes);
 
     PyGILState_Release(pygilstate);
 
@@ -694,7 +728,10 @@ ex_py3file(exarg_T *eap)
      * different options under Windows, meaning that stdio pointers aren't
      * compatible between the two. Yuk.
      *
-     * construct: exec(compile(open('a_filename').read(), 'a_filename', 'exec'))
+     * construct: exec(compile(open('a_filename', 'rb').read(), 'a_filename', 'exec'))
+     *
+     * Using bytes so that Python can detect the source encoding as it normally
+     * does. The doc does not say "compile" accept bytes, though.
      *
      * We need to escape any backslashes or single quotes in the file name, so that
      * Python won't mangle the file name.
@@ -717,8 +754,8 @@ ex_py3file(exarg_T *eap)
 	    return;
 	if (i==0)
 	{
-	    strcpy(p,"').read(),'");
-	    p += 11;
+	    strcpy(p,"','rb').read(),'");
+	    p += 16;
 	}
 	else
 	{
@@ -813,8 +850,8 @@ PythonIO_Fini(void)
 
 static Py_ssize_t BufferLength(PyObject *);
 static PyObject *BufferItem(PyObject *, Py_ssize_t);
-static Py_ssize_t BufferAsItem(PyObject *, Py_ssize_t, PyObject *);
 static PyObject* BufferSubscript(PyObject *self, PyObject* idx);
+static Py_ssize_t BufferAsSubscript(PyObject *self, PyObject* idx, PyObject* val);
 
 
 /* Line range type - Implementation functions
@@ -836,7 +873,7 @@ static PySequenceMethods BufferAsSeq = {
     (ssizeargfunc)	0,		    /* sq_repeat,    x*n      */
     (ssizeargfunc)	BufferItem,	    /* sq_item,      x[i]     */
     0,					    /* was_sq_slice,	 x[i:j]   */
-    (ssizeobjargproc)	BufferAsItem,	    /* sq_ass_item,  x[i]=v   */
+    0,					    /* sq_ass_item,  x[i]=v   */
     0,					    /* sq_ass_slice, x[i:j]=v */
     0,					    /* sq_contains */
     0,					    /* sq_inplace_concat */
@@ -846,7 +883,7 @@ static PySequenceMethods BufferAsSeq = {
 PyMappingMethods BufferAsMapping = {
     /* mp_length	*/ (lenfunc)BufferLength,
     /* mp_subscript     */ (binaryfunc)BufferSubscript,
-    /* mp_ass_subscript */ (objobjargproc)0,
+    /* mp_ass_subscript */ (objobjargproc)BufferAsSubscript,
 };
 
 
@@ -898,6 +935,8 @@ BufferDestructor(PyObject *self)
 
     if (this->buf && this->buf != INVALID_BUFFER_VALUE)
 	this->buf->b_python3_ref = NULL;
+
+    Py_TYPE(self)->tp_free((PyObject*)self);
 }
 
     static PyObject *
@@ -976,15 +1015,6 @@ BufferSlice(PyObject *self, Py_ssize_t lo, Py_ssize_t hi)
 	       (Py_ssize_t)((BufferObject *)(self))->buf->b_ml.ml_line_count);
 }
 
-    static Py_ssize_t
-BufferAsItem(PyObject *self, Py_ssize_t n, PyObject *val)
-{
-    return RBAsItem((BufferObject *)(self), n, val, 1,
-		(Py_ssize_t)((BufferObject *)(self))->buf->b_ml.ml_line_count,
-		NULL);
-}
-
-
     static PyObject *
 BufferSubscript(PyObject *self, PyObject* idx)
 {
@@ -994,19 +1024,45 @@ BufferSubscript(PyObject *self, PyObject* idx)
     } else if (PySlice_Check(idx)) {
 	Py_ssize_t start, stop, step, slicelen;
 
-	if (PySlice_GetIndicesEx((PySliceObject *)idx,
+	if (PySlice_GetIndicesEx(idx,
 	      (Py_ssize_t)((BufferObject *)(self))->buf->b_ml.ml_line_count+1,
 	      &start, &stop,
 	      &step, &slicelen) < 0) {
 	    return NULL;
 	}
-	return BufferSlice(self,start,stop+1);
+	return BufferSlice(self,start,stop);
     } else {
 	PyErr_SetString(PyExc_IndexError, "Index must be int or slice");
 	return NULL;
     }
 }
 
+    static Py_ssize_t
+BufferAsSubscript(PyObject *self, PyObject* idx, PyObject* val)
+{
+    if (PyLong_Check(idx)) {
+	long n = PyLong_AsLong(idx);
+	return RBAsItem((BufferObject *)(self), n, val, 1,
+		    (Py_ssize_t)((BufferObject *)(self))->buf->b_ml.ml_line_count,
+		    NULL);
+    } else if (PySlice_Check(idx)) {
+	Py_ssize_t start, stop, step, slicelen;
+
+	if (PySlice_GetIndicesEx(idx,
+	      (Py_ssize_t)((BufferObject *)(self))->buf->b_ml.ml_line_count+1,
+	      &start, &stop,
+	      &step, &slicelen) < 0) {
+	    return -1;
+	}
+	return RBAsSlice((BufferObject *)(self), start, stop, val, 1,
+			  (PyInt)((BufferObject *)(self))->buf->b_ml.ml_line_count,
+			  NULL);
+    } else {
+	PyErr_SetString(PyExc_IndexError, "Index must be int or slice");
+	return -1;
+    }
+}
+
 static PySequenceMethods RangeAsSeq = {
     (lenfunc)		RangeLength,	 /* sq_length,	  len(x)   */
     (binaryfunc)	0,		 /* RangeConcat, sq_concat,  x+y   */
@@ -1033,6 +1089,7 @@ PyMappingMethods RangeAsMapping = {
 RangeDestructor(PyObject *self)
 {
     Py_DECREF(((RangeObject *)(self))->buf);
+    Py_TYPE(self)->tp_free((PyObject*)self);
 }
 
     static PyObject *
@@ -1070,7 +1127,7 @@ RangeSubscript(PyObject *self, PyObject* idx)
     } else if (PySlice_Check(idx)) {
 	Py_ssize_t start, stop, step, slicelen;
 
-	if (PySlice_GetIndicesEx((PySliceObject *)idx,
+	if (PySlice_GetIndicesEx(idx,
 		((RangeObject *)(self))->end-((RangeObject *)(self))->start+1,
 		&start, &stop,
 		&step, &slicelen) < 0) {
@@ -1160,6 +1217,8 @@ WindowDestructor(PyObject *self)
 
     if (this->win && this->win != INVALID_WINDOW_VALUE)
 	this->win->w_python3_ref = NULL;
+
+    Py_TYPE(self)->tp_free((PyObject*)self);
 }
 
     static PyObject *
@@ -1351,8 +1410,11 @@ PyMODINIT_FUNC Py3Init_vim(void)
     PySys_SetArgv(1, argv);
 
     mod = PyModule_Create(&vimmodule);
+    if (mod == NULL)
+	return NULL;
 
-    VimError = Py_BuildValue("s", "vim.error");
+    VimError = PyErr_NewException("vim.error", NULL, NULL);
+    Py_INCREF(VimError);
 
     PyModule_AddObject(mod, "error", VimError);
     Py_INCREF((PyObject *)(void *)&TheBufferList);
@@ -1405,7 +1467,7 @@ LineToString(const char *str)
     }
     *p = '\0';
 
-    result = PyUnicode_FromStringAndSize(tmp, len);
+    result = PyUnicode_Decode(tmp, len, p_enc, NULL);
 
     vim_free(tmp);
     return result;