diff --git a/contrib/src/sceneeditor/collisionWindow.py b/contrib/src/sceneeditor/collisionWindow.py
index 9155db871a..12136039d5 100644
--- a/contrib/src/sceneeditor/collisionWindow.py
+++ b/contrib/src/sceneeditor/collisionWindow.py
@@ -9,7 +9,6 @@ from seColorEntry import *
 from direct.tkwidgets import VectorWidgets
 from direct.tkwidgets import Floater
 from direct.tkwidgets import Slider
-import string, math, types
 from panda3d.core import *
 
 
diff --git a/contrib/src/sceneeditor/dataHolder.py b/contrib/src/sceneeditor/dataHolder.py
index 4e01ab2fa4..db196dd233 100644
--- a/contrib/src/sceneeditor/dataHolder.py
+++ b/contrib/src/sceneeditor/dataHolder.py
@@ -2,7 +2,7 @@
 # TK and PMW INTERFACE MODULES#
 ###############################
 from direct.showbase.TkGlobal import*
-import Pmw
+import Pmw, sys
 from direct.tkwidgets import Dial
 from direct.tkwidgets import Floater
 
@@ -27,7 +27,6 @@ from direct.actor import Actor
 # Core Python Modules         #
 ###############################
 import os
-import string
 import sys
 
 import seParticleEffect
diff --git a/contrib/src/sceneeditor/lightingPanel.py b/contrib/src/sceneeditor/lightingPanel.py
index eeb8cafa20..d3eb2a5c0e 100644
--- a/contrib/src/sceneeditor/lightingPanel.py
+++ b/contrib/src/sceneeditor/lightingPanel.py
@@ -7,7 +7,7 @@ from direct.tkwidgets.AppShell import AppShell
 from seColorEntry import *
 from direct.tkwidgets.VectorWidgets import Vector3Entry
 from direct.tkwidgets.Slider import Slider
-import sys, math, types, Pmw
+import sys, Pmw
 from panda3d.core import *
 
 if sys.version_info >= (3, 0):
diff --git a/contrib/src/sceneeditor/quad.py b/contrib/src/sceneeditor/quad.py
index 6f4fcf03d0..a44bbe879e 100644
--- a/contrib/src/sceneeditor/quad.py
+++ b/contrib/src/sceneeditor/quad.py
@@ -10,7 +10,7 @@ from direct.showbase.ShowBaseGlobal import *
 from direct.interval.IntervalGlobal import *
 from direct.showbase.DirectObject import DirectObject
 from panda3d.core import *
-import math
+from direct.task import Task
 
 
 class ViewPort:
diff --git a/contrib/src/sceneeditor/sceneEditor.py b/contrib/src/sceneeditor/sceneEditor.py
index 1565e9eaed..3c4d291bbd 100644
--- a/contrib/src/sceneeditor/sceneEditor.py
+++ b/contrib/src/sceneeditor/sceneEditor.py
@@ -36,17 +36,12 @@ from seBlendAnimPanel import *
 from controllerWindow import *
 from AlignTool import *
 
-
-
-import os
-import string
 from direct.tkwidgets import Dial
 from direct.tkwidgets import Floater
 from direct.tkwidgets import Slider
 from direct.actor import Actor
 import seAnimPanel
 from direct.task import Task
-import math
 
 #################################################################
 # All scene and windows object will be stored in here.
diff --git a/contrib/src/sceneeditor/seAnimPanel.py b/contrib/src/sceneeditor/seAnimPanel.py
index 2dd3ceee53..ec7f8faf21 100644
--- a/contrib/src/sceneeditor/seAnimPanel.py
+++ b/contrib/src/sceneeditor/seAnimPanel.py
@@ -5,9 +5,7 @@
 # Import Tkinter, Pmw, and the floater code from this directory tree.
 from direct.tkwidgets.AppShell import *
 from direct.showbase.TkGlobal import *
-import string
-import math
-import types
+import sys
 from direct.task import Task
 
 if sys.version_info >= (3, 0):
@@ -407,7 +405,7 @@ class AnimPanel(AppShell):
         #################################################################
         if self.animName in self['animList']:
             # Convert scale value to float
-            frame = string.atof(frame)
+            frame = float(frame)
             # Now convert t to seconds for offset calculations
             if self.unitsVar.get() == FRAMES:
                 frame = frame / self.fps
diff --git a/contrib/src/sceneeditor/seBlendAnimPanel.py b/contrib/src/sceneeditor/seBlendAnimPanel.py
index 2ab28210c5..27b9c30957 100644
--- a/contrib/src/sceneeditor/seBlendAnimPanel.py
+++ b/contrib/src/sceneeditor/seBlendAnimPanel.py
@@ -5,9 +5,7 @@
 # Import Tkinter, Pmw, and the floater code from this directory tree.
 from direct.tkwidgets.AppShell import *
 from direct.showbase.TkGlobal import *
-import string
-import math
-import types
+import sys
 from direct.task import Task
 
 if sys.version_info >= (3, 0):
@@ -431,7 +429,7 @@ class BlendAnimPanel(AppShell):
         #################################################################
         if (self.animNameA in self['animList'])and(self.animNameB in self['animList']):
             # Convert scale value to float
-            frame = string.atof(frame)
+            frame = float(frame)
             # Now convert t to seconds for offset calculations
             if self.unitsVar.get() == FRAMES:
                 frame = frame / self.fps
diff --git a/contrib/src/sceneeditor/seCameraControl.py b/contrib/src/sceneeditor/seCameraControl.py
index 95237db8be..17bcedaf36 100644
--- a/contrib/src/sceneeditor/seCameraControl.py
+++ b/contrib/src/sceneeditor/seCameraControl.py
@@ -16,6 +16,7 @@ from direct.directtools.DirectUtil import *
 from seGeometry import *
 from direct.directtools.DirectGlobals import *
 from direct.task import Task
+import math
 
 CAM_MOVE_DURATION = 1.2
 COA_MARKER_SF = 0.0075
diff --git a/contrib/src/sceneeditor/seFileSaver.py b/contrib/src/sceneeditor/seFileSaver.py
index 9d58fa0580..30c078493b 100644
--- a/contrib/src/sceneeditor/seFileSaver.py
+++ b/contrib/src/sceneeditor/seFileSaver.py
@@ -8,7 +8,6 @@ from panda3d.core import *
 from direct.showbase.ShowBaseGlobal import *
 import os
 import shutil
-import string
 
 ####################################################################################################################################################
 #### These modules are modified versions of Disney's equivalent modules
diff --git a/contrib/src/sceneeditor/seGrid.py b/contrib/src/sceneeditor/seGrid.py
index b9785df261..cacff7299f 100644
--- a/contrib/src/sceneeditor/seGrid.py
+++ b/contrib/src/sceneeditor/seGrid.py
@@ -14,6 +14,7 @@
 from direct.showbase.DirectObject import *
 from direct.directtools.DirectUtil import *
 from seGeometry import *
+import math
 
 class DirectGrid(NodePath,DirectObject):
     def __init__(self):
diff --git a/contrib/src/sceneeditor/seLights.py b/contrib/src/sceneeditor/seLights.py
index 2353512af5..ce2436625e 100644
--- a/contrib/src/sceneeditor/seLights.py
+++ b/contrib/src/sceneeditor/seLights.py
@@ -5,7 +5,6 @@
 from direct.showbase.DirectObject import *
 from direct.directtools import DirectUtil
 from panda3d.core import *
-import string
 
 
 class seLight(NodePath):
diff --git a/contrib/src/sceneeditor/seManipulation.py b/contrib/src/sceneeditor/seManipulation.py
index 4d0c781b1e..a20a323749 100644
--- a/contrib/src/sceneeditor/seManipulation.py
+++ b/contrib/src/sceneeditor/seManipulation.py
@@ -17,6 +17,7 @@ from direct.directtools.DirectGlobals import *
 from direct.directtools.DirectUtil import *
 from seGeometry import *
 from direct.task import Task
+import math
 
 class DirectManipulationControl(DirectObject):
     def __init__(self):
@@ -601,7 +602,7 @@ class ObjectHandles(NodePath,DirectObject):
         self.reparentTo(hidden)
 
     def enableHandles(self, handles):
-        if type(handles) == types.ListType:
+        if type(handles) is list:
             for handle in handles:
                 self.enableHandle(handle)
         elif handles == 'x':
@@ -642,7 +643,7 @@ class ObjectHandles(NodePath,DirectObject):
             self.zDiscGroup.reparentTo(self.zHandles)
 
     def disableHandles(self, handles):
-        if type(handles) == types.ListType:
+        if type(handles) is list:
             for handle in handles:
                 self.disableHandle(handle)
         elif handles == 'x':
diff --git a/contrib/src/sceneeditor/seMopathRecorder.py b/contrib/src/sceneeditor/seMopathRecorder.py
index dc8bbd8d22..65edba3880 100644
--- a/contrib/src/sceneeditor/seMopathRecorder.py
+++ b/contrib/src/sceneeditor/seMopathRecorder.py
@@ -25,7 +25,8 @@ from direct.tkwidgets.Slider import Slider
 from direct.tkwidgets.EntryScale import EntryScale
 from direct.tkwidgets.VectorWidgets import Vector2Entry, Vector3Entry
 from direct.tkwidgets.VectorWidgets import ColorEntry
-import os, string, sys, Pmw
+import os, sys, Pmw
+import math
 
 if sys.version_info >= (3, 0):
     from tkinter import Button, Frame, Radiobutton, Checkbutton, Label
@@ -374,7 +375,7 @@ class MopathRecorder(AppShell, DirectObject):
         self.speedEntry.bind(
             '<Return>',
             lambda e = None, s = self: s.setSpeedScale(
-            string.atof(s.speedVar.get())))
+            float(s.speedVar.get())))
         self.speedEntry.pack(side = tkinter.LEFT, expand = 0)
         frame.pack(fill = tkinter.X, expand = 1)
 
diff --git a/contrib/src/sceneeditor/seParticles.py b/contrib/src/sceneeditor/seParticles.py
index a4f0d0e5d6..df79e4ff47 100644
--- a/contrib/src/sceneeditor/seParticles.py
+++ b/contrib/src/sceneeditor/seParticles.py
@@ -3,7 +3,6 @@ from panda3d.physics import *
 from direct.particles.ParticleManagerGlobal import *
 from direct.showbase.PhysicsManagerGlobal import *
 #import OrientedParticleFactory
-import string
 import os
 from direct.directnotify import DirectNotifyGlobal
 import sys
diff --git a/contrib/src/sceneeditor/seSession.py b/contrib/src/sceneeditor/seSession.py
index c8e7a1a20f..2077398070 100644
--- a/contrib/src/sceneeditor/seSession.py
+++ b/contrib/src/sceneeditor/seSession.py
@@ -20,9 +20,9 @@ from seGeometry import *
 from direct.tkpanels import Placer
 from direct.tkwidgets import Slider
 from direct.gui import OnscreenText
-import types
-import string
+from direct.task import Task
 from direct.showbase import Loader
+import math
 
 class SeSession(DirectObject):  ### Customized DirectSession
 
diff --git a/contrib/src/sceneeditor/seTree.py b/contrib/src/sceneeditor/seTree.py
index 9927c11112..81c108fcf3 100644
--- a/contrib/src/sceneeditor/seTree.py
+++ b/contrib/src/sceneeditor/seTree.py
@@ -12,7 +12,7 @@
 #
 #################################################################
 
-import os, sys, string, Pmw
+import os, sys, Pmw
 from direct.showbase.DirectObject import DirectObject
 from panda3d.core import *
 
@@ -221,7 +221,7 @@ class TreeNode:
             self.children[key] = child
             self.kidKeys.append(key)
         # Remove unused children
-        for key in self.children.keys():
+        for key in list(self.children.keys()):
             if key not in self.kidKeys:
                 del(self.children[key])
         cx = x+20
diff --git a/direct/src/stdpy/pickle.py b/direct/src/stdpy/pickle.py
index 03ef1969d0..77390d6853 100644
--- a/direct/src/stdpy/pickle.py
+++ b/direct/src/stdpy/pickle.py
@@ -30,19 +30,26 @@ from copyreg import dispatch_table
 # with the local pickle.py.
 pickle = __import__('pickle')
 
-class Pickler(pickle.Pickler):
+BasePickler = pickle._Pickler
+BaseUnpickler = pickle._Unpickler
+
+
+class _Pickler(BasePickler):
 
     def __init__(self, *args, **kw):
         self.bamWriter = BamWriter()
-        pickle.Pickler.__init__(self, *args, **kw)
+        BasePickler.__init__(self, *args, **kw)
 
     # We have to duplicate most of the save() method, so we can add
     # support for __reduce_persist__().
 
-    def save(self, obj):
+    def save(self, obj, save_persistent_id=True):
+        if self.proto >= 4:
+            self.framer.commit_frame()
+
         # Check for persistent id (defined by a subclass)
         pid = self.persistent_id(obj)
-        if pid:
+        if pid is not None and save_persistent_id:
             self.save_pers(pid)
             return
 
@@ -109,11 +116,12 @@ class Pickler(pickle.Pickler):
         # Save the reduce() output and finally memoize the object
         self.save_reduce(obj=obj, *rv)
 
-class Unpickler(pickle.Unpickler):
+
+class Unpickler(BaseUnpickler):
 
     def __init__(self, *args, **kw):
         self.bamReader = BamReader()
-        pickle.Unpickler.__init__(self, *args, **kw)
+        BaseUnpickler.__init__(self, *args, **kw)
 
     # Duplicate the load_reduce() function, to provide a special case
     # for the reduction function.
@@ -123,9 +131,10 @@ class Unpickler(pickle.Unpickler):
         args = stack.pop()
         func = stack[-1]
 
-        # If the function name ends with "Persist", then assume the
+        # If the function name ends with "_persist", then assume the
         # function wants the Unpickler as the first parameter.
-        if func.__name__.endswith('Persist'):
+        func_name = func.__name__
+        if func_name.endswith('_persist') or func_name.endswith('Persist'):
             value = func(self, *args)
         else:
             # Otherwise, use the existing pickle convention.
@@ -133,9 +142,26 @@ class Unpickler(pickle.Unpickler):
 
         stack[-1] = value
 
-    #FIXME: how to replace in Python 3?
-    if sys.version_info < (3, 0):
-        pickle.Unpickler.dispatch[pickle.REDUCE] = load_reduce
+    BaseUnpickler.dispatch[pickle.REDUCE[0]] = load_reduce
+
+
+if sys.version_info >= (3, 8):
+    # In Python 3.8 and up, we can use the C implementation of Pickler, which
+    # supports a reducer_override method.
+    class Pickler(pickle.Pickler):
+        def __init__(self, *args, **kw):
+            self.bamWriter = BamWriter()
+            pickle.Pickler.__init__(self, *args, **kw)
+
+        def reducer_override(self, obj):
+            reduce = getattr(obj, "__reduce_persist__", None)
+            if reduce:
+                return reduce(self)
+
+            return NotImplemented
+else:
+    # Otherwise, we have to use our custom version that overrides save().
+    Pickler = _Pickler
 
 
 # Shorthands
diff --git a/tests/stdpy/test_pickle.py b/tests/stdpy/test_pickle.py
new file mode 100644
index 0000000000..303c5559c1
--- /dev/null
+++ b/tests/stdpy/test_pickle.py
@@ -0,0 +1,11 @@
+from direct.stdpy.pickle import dumps, loads
+
+
+def test_reduce_persist():
+    from panda3d.core import NodePath
+
+    parent = NodePath("parent")
+    child = parent.attach_new_node("child")
+
+    parent2, child2 = loads(dumps([parent, child]))
+    assert tuple(parent2.children) == (child2,)