diff --git a/ffmpeg/__init__.py b/ffmpeg/__init__.py
index 1953609..154d8b6 100644
--- a/ffmpeg/__init__.py
+++ b/ffmpeg/__init__.py
@@ -1,6 +1,8 @@
 from __future__ import unicode_literals
+
 from . import _filters, _ffmpeg, _run
 from ._filters import *
 from ._ffmpeg import *
 from ._run import *
+
 __all__ = _filters.__all__ + _ffmpeg.__all__ + _run.__all__
diff --git a/ffmpeg/_ffmpeg.py b/ffmpeg/_ffmpeg.py
index 8dc6c87..968e793 100644
--- a/ffmpeg/_ffmpeg.py
+++ b/ffmpeg/_ffmpeg.py
@@ -1,4 +1,5 @@
 from __future__ import unicode_literals
+
 from .nodes import (
     filter_operator,
     GlobalNode,
diff --git a/ffmpeg/_filters.py b/ffmpeg/_filters.py
index 79949ab..a422f00 100644
--- a/ffmpeg/_filters.py
+++ b/ffmpeg/_filters.py
@@ -1,4 +1,5 @@
 from __future__ import unicode_literals
+
 from .nodes import (
     FilterNode,
     filter_operator,
diff --git a/ffmpeg/_utils.py b/ffmpeg/_utils.py
index 04f2add..06c5765 100644
--- a/ffmpeg/_utils.py
+++ b/ffmpeg/_utils.py
@@ -1,4 +1,8 @@
-import hashlib
+from __future__ import unicode_literals
+
+from builtins import str
+from past.builtins import basestring
+import hashlib
 
 
 def _recursive_repr(item):
diff --git a/ffmpeg/dag.py b/ffmpeg/dag.py
index c8a634e..3ce3891 100644
--- a/ffmpeg/dag.py
+++ b/ffmpeg/dag.py
@@ -1,3 +1,5 @@
+from __future__ import unicode_literals
+
 from ._utils import get_hash, get_hash_int
 from builtins import object
 from collections import namedtuple
@@ -72,14 +74,14 @@ DagEdge = namedtuple('DagEdge', ['downstream_node', 'downstream_label', 'upstrea
 
 def get_incoming_edges(downstream_node, incoming_edge_map):
     edges = []
-    for downstream_label, (upstream_node, upstream_label) in incoming_edge_map.items():
+    for downstream_label, (upstream_node, upstream_label) in list(incoming_edge_map.items()):
         edges += [DagEdge(downstream_node, downstream_label, upstream_node, upstream_label)]
     return edges
 
 
 def get_outgoing_edges(upstream_node, outgoing_edge_map):
     edges = []
-    for upstream_label, downstream_infos in outgoing_edge_map.items():
+    for upstream_label, downstream_infos in list(outgoing_edge_map.items()):
         for (downstream_node, downstream_label) in downstream_infos:
             edges += [DagEdge(downstream_node, downstream_label, upstream_node, upstream_label)]
     return edges
@@ -91,7 +93,7 @@ class KwargReprNode(DagNode):
     @property
     def __upstream_hashes(self):
         hashes = []
-        for downstream_label, (upstream_node, upstream_label) in self.incoming_edge_map.items():
+        for downstream_label, (upstream_node, upstream_label) in list(self.incoming_edge_map.items()):
             hashes += [hash(x) for x in [downstream_label, upstream_node, upstream_label]]
         return hashes
 
diff --git a/ffmpeg/nodes.py b/ffmpeg/nodes.py
index b458fae..bc1d55d 100644
--- a/ffmpeg/nodes.py
+++ b/ffmpeg/nodes.py
@@ -1,5 +1,6 @@
 from __future__ import unicode_literals
 
+from builtins import object
 from .dag import KwargReprNode
 from ._utils import get_hash_int
 
@@ -49,7 +50,7 @@ class Node(KwargReprNode):
 
     @classmethod
     def __check_input_types(cls, stream_map, incoming_stream_types):
-        for stream in stream_map.values():
+        for stream in list(stream_map.values()):
             if not _is_of_types(stream, incoming_stream_types):
                 raise TypeError('Expected incoming stream(s) to be of one of the following types: {}; got {}'
                     .format(_get_types_str(incoming_stream_types), type(stream)))
@@ -69,7 +70,7 @@ class Node(KwargReprNode):
     @classmethod
     def __get_incoming_edge_map(cls, stream_map):
         incoming_edge_map = {}
-        for downstream_label, upstream in stream_map.items():
+        for downstream_label, upstream in list(stream_map.items()):
             incoming_edge_map[downstream_label] = (upstream.node, upstream.label)
         return incoming_edge_map