diff --git a/jedi/api/__init__.py b/jedi/api/__init__.py
index 5ee560f3..d306c26a 100644
--- a/jedi/api/__init__.py
+++ b/jedi/api/__init__.py
@@ -148,7 +148,7 @@ class Script(object):
         comps = []
         comp_dct = {}
         for c, s in set(completions):
-            n = c.names[-1]
+            n = str(c.names[-1])
             if settings.case_insensitive_completion \
                     and n.lower().startswith(like.lower()) \
                     or n.startswith(like):
diff --git a/jedi/api/classes.py b/jedi/api/classes.py
index 5e1d386c..96c296fb 100644
--- a/jedi/api/classes.py
+++ b/jedi/api/classes.py
@@ -323,7 +323,7 @@ class Completion(BaseDefinition):
         if isinstance(self._base, pr.Param):
             append += '='
 
-        name = self._name.names[-1]
+        name = str(self._name.names[-1])
         if like_name:
             name = name[self._like_name_length:]
         return dot + name + append
diff --git a/jedi/api/interpreter.py b/jedi/api/interpreter.py
index 374c4797..cf38dff5 100644
--- a/jedi/api/interpreter.py
+++ b/jedi/api/interpreter.py
@@ -44,14 +44,14 @@ class LazyName(helpers.FakeName):
         else:
             try:
                 o = obj.__objclass__
-                parser_path.append(pr.NamePart(obj.__name__, None, None))
+                parser_path.append(pr.NamePart(obj.__name__, None, (None, None)))
                 obj = o
             except AttributeError:
                 pass
 
             try:
                 module_name = obj.__module__
-                parser_path.insert(0, pr.NamePart(obj.__name__, None, None))
+                parser_path.insert(0, pr.NamePart(obj.__name__, None, (None, None)))
             except AttributeError:
                 # Unfortunately in some cases like `int` there's no __module__
                 module = builtins
diff --git a/jedi/api/usages.py b/jedi/api/usages.py
index ea976298..bc2be942 100644
--- a/jedi/api/usages.py
+++ b/jedi/api/usages.py
@@ -71,7 +71,7 @@ def usages(evaluator, definitions, search_name, mods):
     compare_definitions = compare_array(definitions)
     mods |= set([d.get_parent_until() for d in definitions])
     names = []
-    for m in imports.get_modules_containing_name(mods, search_name):
+    for m in imports.get_modules_containing_name(mods, str(search_name)):
         try:
             stmts = m.used_names[search_name]
         except KeyError:
diff --git a/jedi/evaluate/__init__.py b/jedi/evaluate/__init__.py
index 7a3afcb7..548ba34e 100644
--- a/jedi/evaluate/__init__.py
+++ b/jedi/evaluate/__init__.py
@@ -348,6 +348,7 @@ class Evaluator(object):
 
 def filter_private_variable(scope, call_scope, var_name):
     """private variables begin with a double underline `__`"""
+    var_name = str(var_name)  # var_name could be a NamePart
     if isinstance(var_name, (str, unicode)) and isinstance(scope, er.Instance)\
             and var_name.startswith('__') and not var_name.endswith('__'):
         s = call_scope.get_parent_until((pr.Class, er.Instance, compiled.CompiledObject))
diff --git a/jedi/evaluate/imports.py b/jedi/evaluate/imports.py
index ad5727ce..ef02f556 100644
--- a/jedi/evaluate/imports.py
+++ b/jedi/evaluate/imports.py
@@ -63,6 +63,7 @@ class ImportPath(pr.Base):
                 self.import_path.append(import_stmt.namespace.names[0])
             else:
                 self.import_path += import_stmt.namespace.names
+        self.import_path = [str(name_part) for name_part in self.import_path]
 
         for i in range(kill_count + int(is_like_search)):
             self.import_path.pop()
diff --git a/jedi/parser/representation.py b/jedi/parser/representation.py
index 55ad20ab..7399aa22 100644
--- a/jedi/parser/representation.py
+++ b/jedi/parser/representation.py
@@ -538,7 +538,7 @@ class Function(Scope):
 
         :rtype: str
         """
-        l = (funcname or self.name.names[-1]) + '('
+        l = str(funcname or self.name.names[-1]) + '('
         lines = []
         for (i, p) in enumerate(self.params):
             code = p.get_code(False)
@@ -1386,31 +1386,45 @@ class Array(StatementElement):
         return "<%s: %s%s>" % (type(self).__name__, typ, self.values)
 
 
-class NamePart(str):
+class NamePart(object):
     """
     A string. Sometimes it is important to know if the string belongs to a name
     or not.
     """
     # Unfortunately there's no way to use slots for str (non-zero __itemsize__)
     # -> http://utcc.utoronto.ca/~cks/space/blog/python/IntSlotsPython3k
-    #__slots__ = ('_start_pos', 'parent')
-    def __new__(cls, s, parent, start_pos):
-        self = super(NamePart, cls).__new__(cls, s)
-        self._start_pos = start_pos
+    # Therefore don't subclass `str`.
+    __slots__ = ('parent', 'string', '_line', '_column')
+
+    def __init__(self, string, parent, start_pos):
+        if isinstance(string, NamePart):
+            # may happen, because this class used to be a `str`.
+            string = string.string
+        self.string = string
         self.parent = parent
-        return self
+        self._line = start_pos[0]
+        self._column = start_pos[1]
+
+    def __str__(self):
+        return self.string
+
+    def __repr__(self):
+        return "<%s: %s>" % (type(self).__name__, self.string)
+
+    def __eq__(self, other):
+        return self.string == other
+
+    def __hash__(self):
+        return hash(self.string)
 
     @property
     def start_pos(self):
         offset = self.parent._sub_module.line_offset
-        return offset + self._start_pos[0], self._start_pos[1]
+        return offset + self._line, self._column
 
     @property
     def end_pos(self):
-        return self.start_pos[0], self.start_pos[1] + len(self)
-
-    def __getnewargs__(self):
-        return str(self), self.parent, self._start_pos
+        return self.start_pos[0], self.start_pos[1] + len(self.string)
 
 
 class Name(Simple):
@@ -1431,7 +1445,7 @@ class Name(Simple):
 
     def get_code(self):
         """ Returns the names in a full string format """
-        return ".".join(self.names)
+        return ".".join(str(n) for n in self.names)
 
     @property
     def docstr(self):