diff --git a/docs/code/tumblelog.py b/docs/code/tumblelog.py
index c10160ea..796336e6 100644
--- a/docs/code/tumblelog.py
+++ b/docs/code/tumblelog.py
@@ -45,27 +45,27 @@ post2.link_url = 'http://tractiondigital.com/labs/mongoengine/docs'
 post2.tags = ['mongoengine']
 post2.save()
 
-print 'ALL POSTS'
-print
+print('ALL POSTS')
+print()
 for post in Post.objects:
-    print post.title
+    print(post.title)
     #print '=' * post.title.count()
-    print "=" * 20
+    print("=" * 20)
 
     if isinstance(post, TextPost):
-        print post.content
+        print(post.content)
 
     if isinstance(post, LinkPost):
-        print 'Link:', post.link_url
+        print('Link:', post.link_url)
 
-    print
-print
+    print()
+print()
 
-print 'POSTS TAGGED \'MONGODB\''
-print
+print('POSTS TAGGED \'MONGODB\'')
+print()
 for post in Post.objects(tags='mongodb'):
-    print post.title
-print
+    print(post.title)
+print()
 
 num_posts = Post.objects(tags='mongodb').count()
-print 'Found %d posts with tag "mongodb"' % num_posts
+print('Found %d posts with tag "mongodb"' % num_posts)
diff --git a/mongoengine/base/common.py b/mongoengine/base/common.py
index f80471ef..dd177920 100644
--- a/mongoengine/base/common.py
+++ b/mongoengine/base/common.py
@@ -3,10 +3,10 @@ from mongoengine.errors import NotRegistered
 __all__ = ('UPDATE_OPERATORS', 'get_document', '_document_registry')
 
 
-UPDATE_OPERATORS = set(['set', 'unset', 'inc', 'dec', 'mul',
-                        'pop', 'push', 'push_all', 'pull',
-                        'pull_all', 'add_to_set', 'set_on_insert',
-                        'min', 'max', 'rename'])
+UPDATE_OPERATORS = {'set', 'unset', 'inc', 'dec', 'mul',
+                    'pop', 'push', 'push_all', 'pull',
+                    'pull_all', 'add_to_set', 'set_on_insert',
+                    'min', 'max', 'rename'}
 
 
 _document_registry = {}
diff --git a/mongoengine/base/datastructures.py b/mongoengine/base/datastructures.py
index db292f14..0197ad10 100644
--- a/mongoengine/base/datastructures.py
+++ b/mongoengine/base/datastructures.py
@@ -377,7 +377,7 @@ class EmbeddedDocumentList(BaseList):
 
 class StrictDict(object):
     __slots__ = ()
-    _special_fields = set(['get', 'pop', 'iteritems', 'items', 'keys', 'create'])
+    _special_fields = {'get', 'pop', 'iteritems', 'items', 'keys', 'create'}
     _classes = {}
 
     def __init__(self, **kwargs):
diff --git a/mongoengine/base/document.py b/mongoengine/base/document.py
index 85906a3e..fdebab23 100644
--- a/mongoengine/base/document.py
+++ b/mongoengine/base/document.py
@@ -302,7 +302,7 @@ class BaseDocument(object):
         data['_cls'] = self._class_name
 
         # only root fields ['test1.a', 'test2'] => ['test1', 'test2']
-        root_fields = set([f.split('.')[0] for f in fields])
+        root_fields = {f.split('.')[0] for f in fields}
 
         for field_name in self:
             if root_fields and field_name not in root_fields:
@@ -567,7 +567,7 @@ class BaseDocument(object):
                     continue
                 elif isinstance(field, SortedListField) and field._ordering:
                     # if ordering is affected whole list is changed
-                    if any(map(lambda d: field._ordering in d._changed_fields, data)):
+                    if any(field._ordering in d._changed_fields for d in data):
                         changed_fields.append(db_field_name)
                         continue
 
diff --git a/mongoengine/base/fields.py b/mongoengine/base/fields.py
index d25d4305..a0726aa6 100644
--- a/mongoengine/base/fields.py
+++ b/mongoengine/base/fields.py
@@ -501,7 +501,7 @@ class GeoJsonBaseField(BaseField):
     def validate(self, value):
         """Validate the GeoJson object based on its type."""
         if isinstance(value, dict):
-            if set(value.keys()) == set(['type', 'coordinates']):
+            if set(value.keys()) == {'type', 'coordinates'}:
                 if value['type'] != self._type:
                     self.error('%s type must be "%s"' %
                                (self._name, self._type))
diff --git a/mongoengine/dereference.py b/mongoengine/dereference.py
index 40bc72b2..6c993223 100644
--- a/mongoengine/dereference.py
+++ b/mongoengine/dereference.py
@@ -146,7 +146,7 @@ class DeReference(object):
                 for key, doc in references.iteritems():
                     object_map[(col_name, key)] = doc
             else:  # Generic reference: use the refs data to convert to document
-                if isinstance(doc_type, (ListField, DictField, MapField,)):
+                if isinstance(doc_type, (ListField, DictField, MapField)):
                     continue
 
                 refs = [dbref for dbref in dbrefs
diff --git a/mongoengine/document.py b/mongoengine/document.py
index 25af273d..cdeed4c6 100644
--- a/mongoengine/document.py
+++ b/mongoengine/document.py
@@ -39,7 +39,7 @@ class InvalidCollectionError(Exception):
     pass
 
 
-class EmbeddedDocument(BaseDocument):
+class EmbeddedDocument(six.with_metaclass(DocumentMetaclass, BaseDocument)):
     """A :class:`~mongoengine.Document` that isn't stored in its own
     collection.  :class:`~mongoengine.EmbeddedDocument`\ s should be used as
     fields on :class:`~mongoengine.Document`\ s through the
@@ -58,7 +58,6 @@ class EmbeddedDocument(BaseDocument):
     # The __metaclass__ attribute is removed by 2to3 when running with Python3
     # my_metaclass is defined so that metaclass can be queried in Python 2 & 3
     my_metaclass = DocumentMetaclass
-    __metaclass__ = DocumentMetaclass
 
     # A generic embedded document doesn't have any immutable properties
     # that describe it uniquely, hence it shouldn't be hashable. You can
@@ -95,7 +94,7 @@ class EmbeddedDocument(BaseDocument):
         self._instance.reload(*args, **kwargs)
 
 
-class Document(BaseDocument):
+class Document(six.with_metaclass(TopLevelDocumentMetaclass, BaseDocument)):
     """The base class used for defining the structure and properties of
     collections of documents stored in MongoDB. Inherit from this class, and
     add fields as class attributes to define a document's structure.
@@ -150,7 +149,6 @@ class Document(BaseDocument):
     # The __metaclass__ attribute is removed by 2to3 when running with Python3
     # my_metaclass is defined so that metaclass can be queried in Python 2 & 3
     my_metaclass = TopLevelDocumentMetaclass
-    __metaclass__ = TopLevelDocumentMetaclass
 
     __slots__ = ('__objects',)
 
@@ -996,7 +994,7 @@ class Document(BaseDocument):
         return {'missing': missing, 'extra': extra}
 
 
-class DynamicDocument(Document):
+class DynamicDocument(six.with_metaclass(TopLevelDocumentMetaclass, Document)):
     """A Dynamic Document class allowing flexible, expandable and uncontrolled
     schemas.  As a :class:`~mongoengine.Document` subclass, acts in the same
     way as an ordinary document but has expanded style properties.  Any data
@@ -1013,7 +1011,6 @@ class DynamicDocument(Document):
     # The __metaclass__ attribute is removed by 2to3 when running with Python3
     # my_metaclass is defined so that metaclass can be queried in Python 2 & 3
     my_metaclass = TopLevelDocumentMetaclass
-    __metaclass__ = TopLevelDocumentMetaclass
 
     _dynamic = True
 
@@ -1029,7 +1026,7 @@ class DynamicDocument(Document):
             super(DynamicDocument, self).__delattr__(*args, **kwargs)
 
 
-class DynamicEmbeddedDocument(EmbeddedDocument):
+class DynamicEmbeddedDocument(six.with_metaclass(DocumentMetaclass, EmbeddedDocument)):
     """A Dynamic Embedded Document class allowing flexible, expandable and
     uncontrolled schemas. See :class:`~mongoengine.DynamicDocument` for more
     information about dynamic documents.
@@ -1038,7 +1035,6 @@ class DynamicEmbeddedDocument(EmbeddedDocument):
     # The __metaclass__ attribute is removed by 2to3 when running with Python3
     # my_metaclass is defined so that metaclass can be queried in Python 2 & 3
     my_metaclass = DocumentMetaclass
-    __metaclass__ = DocumentMetaclass
 
     _dynamic = True
 
diff --git a/mongoengine/fields.py b/mongoengine/fields.py
index 244551d2..f794edff 100644
--- a/mongoengine/fields.py
+++ b/mongoengine/fields.py
@@ -24,6 +24,7 @@ try:
 except ImportError:
     Int64 = long
 
+
 from mongoengine.base import (BaseDocument, BaseField, ComplexBaseField,
                               GeoJsonBaseField, LazyReference, ObjectIdField,
                               get_document)
@@ -41,6 +42,12 @@ except ImportError:
     Image = None
     ImageOps = None
 
+if six.PY3:
+    # Useless as long as 2to3 gets executed
+    # as it turns `long` into `int` blindly
+    long = int
+
+
 __all__ = (
     'StringField', 'URLField', 'EmailField', 'IntField', 'LongField',
     'FloatField', 'DecimalField', 'BooleanField', 'DateTimeField', 'DateField',
@@ -597,7 +604,7 @@ class ComplexDateTimeField(StringField):
         >>> ComplexDateTimeField()._convert_from_string(a)
         datetime.datetime(2011, 6, 8, 20, 26, 24, 92284)
         """
-        values = map(int, data.split(self.separator))
+        values = [int(d) for d in data.split(self.separator)]
         return datetime.datetime(*values)
 
     def __get__(self, instance, owner):
@@ -1525,9 +1532,11 @@ class GridFSProxy(object):
     def __get__(self, instance, value):
         return self
 
-    def __nonzero__(self):
+    def __bool__(self):
         return bool(self.grid_id)
 
+    __nonzero__ = __bool__  # For Py2 support
+
     def __getstate__(self):
         self_dict = self.__dict__
         self_dict['_fs'] = None
diff --git a/mongoengine/queryset/base.py b/mongoengine/queryset/base.py
index 6fddc381..0be48654 100644
--- a/mongoengine/queryset/base.py
+++ b/mongoengine/queryset/base.py
@@ -2,7 +2,6 @@ from __future__ import absolute_import
 
 import copy
 import itertools
-import operator
 import pprint
 import re
 import warnings
@@ -209,14 +208,12 @@ class BaseQuerySet(object):
         queryset = self.order_by()
         return False if queryset.first() is None else True
 
-    def __nonzero__(self):
-        """Avoid to open all records in an if stmt in Py2."""
-        return self._has_data()
-
     def __bool__(self):
         """Avoid to open all records in an if stmt in Py3."""
         return self._has_data()
 
+    __nonzero__ = __bool__  # For Py2 support
+
     # Core functions
 
     def all(self):
@@ -269,13 +266,13 @@ class BaseQuerySet(object):
         queryset = queryset.filter(*q_objs, **query)
 
         try:
-            result = queryset.next()
+            result = six.next(queryset)
         except StopIteration:
             msg = ('%s matching query does not exist.'
                    % queryset._document._class_name)
             raise queryset._document.DoesNotExist(msg)
         try:
-            queryset.next()
+            six.next(queryset)
         except StopIteration:
             return result
 
@@ -1478,13 +1475,13 @@ class BaseQuerySet(object):
 
     # Iterator helpers
 
-    def next(self):
+    def __next__(self):
         """Wrap the result in a :class:`~mongoengine.Document` object.
         """
         if self._limit == 0 or self._none:
             raise StopIteration
 
-        raw_doc = self._cursor.next()
+        raw_doc = six.next(self._cursor)
 
         if self._as_pymongo:
             return self._get_as_pymongo(raw_doc)
@@ -1498,6 +1495,8 @@ class BaseQuerySet(object):
 
         return doc
 
+    next = __next__     # For Python2 support
+
     def rewind(self):
         """Rewind the cursor to its unevaluated state.
 
diff --git a/mongoengine/queryset/field_list.py b/mongoengine/queryset/field_list.py
index 0524c3bb..dba724af 100644
--- a/mongoengine/queryset/field_list.py
+++ b/mongoengine/queryset/field_list.py
@@ -63,9 +63,11 @@ class QueryFieldList(object):
             self._only_called = True
         return self
 
-    def __nonzero__(self):
+    def __bool__(self):
         return bool(self.fields)
 
+    __nonzero__ = __bool__  # For Py2 support
+
     def as_dict(self):
         field_list = {field: self.value for field in self.fields}
         if self.slice:
diff --git a/mongoengine/queryset/manager.py b/mongoengine/queryset/manager.py
index 199205e9..f93dbb43 100644
--- a/mongoengine/queryset/manager.py
+++ b/mongoengine/queryset/manager.py
@@ -36,7 +36,7 @@ class QuerySetManager(object):
         queryset_class = owner._meta.get('queryset_class', self.default)
         queryset = queryset_class(owner, owner._get_collection())
         if self.get_queryset:
-            arg_count = self.get_queryset.func_code.co_argcount
+            arg_count = self.get_queryset.__code__.co_argcount
             if arg_count == 1:
                 queryset = self.get_queryset(queryset)
             elif arg_count == 2:
diff --git a/mongoengine/queryset/queryset.py b/mongoengine/queryset/queryset.py
index 1aadfb76..f9fed7b7 100644
--- a/mongoengine/queryset/queryset.py
+++ b/mongoengine/queryset/queryset.py
@@ -115,7 +115,7 @@ class QuerySet(BaseQuerySet):
         # the result cache.
         try:
             for _ in six.moves.range(ITER_CHUNK_SIZE):
-                self._result_cache.append(self.next())
+                self._result_cache.append(six.next(self))
         except StopIteration:
             # Getting this exception means there are no more docs in the
             # db cursor. Set _has_more to False so that we can use that
@@ -170,7 +170,7 @@ class QuerySetNoCache(BaseQuerySet):
         data = []
         for _ in six.moves.range(REPR_OUTPUT_SIZE + 1):
             try:
-                data.append(self.next())
+                data.append(six.next(self))
             except StopIteration:
                 break
 
diff --git a/setup.py b/setup.py
index 98964d19..c7632ce3 100644
--- a/setup.py
+++ b/setup.py
@@ -44,9 +44,8 @@ CLASSIFIERS = [
     "Programming Language :: Python :: 2",
     "Programming Language :: Python :: 2.7",
     "Programming Language :: Python :: 3",
-    "Programming Language :: Python :: 3.3",
-    "Programming Language :: Python :: 3.4",
     "Programming Language :: Python :: 3.5",
+    "Programming Language :: Python :: 3.6",
     "Programming Language :: Python :: Implementation :: CPython",
     "Programming Language :: Python :: Implementation :: PyPy",
     'Topic :: Database',
diff --git a/tests/__init__.py b/tests/__init__.py
index eab0ddc7..08db7186 100644
--- a/tests/__init__.py
+++ b/tests/__init__.py
@@ -1,4 +1,4 @@
-from all_warnings import AllWarnings
-from document import *
-from queryset import *
-from fields import *
+from .all_warnings import AllWarnings
+from .document import *
+from .queryset import *
+from .fields import *
diff --git a/tests/document/__init__.py b/tests/document/__init__.py
index f71376ea..dc35c969 100644
--- a/tests/document/__init__.py
+++ b/tests/document/__init__.py
@@ -1,13 +1,13 @@
 import unittest
 
-from class_methods import *
-from delta import *
-from dynamic import *
-from indexes import *
-from inheritance import *
-from instance import *
-from json_serialisation import *
-from validation import *
+from .class_methods import *
+from .delta import *
+from .dynamic import *
+from .indexes import *
+from .inheritance import *
+from .instance import *
+from .json_serialisation import *
+from .validation import *
 
 if __name__ == '__main__':
     unittest.main()
diff --git a/tests/fields/__init__.py b/tests/fields/__init__.py
index 8e0640db..4994d0c6 100644
--- a/tests/fields/__init__.py
+++ b/tests/fields/__init__.py
@@ -1,3 +1,3 @@
-from fields import *
-from file_tests import *
-from geo import *
+from .fields import *
+from .file_tests import *
+from .geo import *
diff --git a/tests/queryset/__init__.py b/tests/queryset/__init__.py
index c36b2684..31016966 100644
--- a/tests/queryset/__init__.py
+++ b/tests/queryset/__init__.py
@@ -1,6 +1,6 @@
-from transform import *
-from field_list import *
-from queryset import *
-from visitor import *
-from geo import *
-from modify import *
\ No newline at end of file
+from .transform import *
+from .field_list import *
+from .queryset import *
+from .visitor import *
+from .geo import *
+from .modify import *