Can not start the vpython backend (Windows 7 64bit, Python 3.8.8.0)

[asmwarrior]

Hi, I have those packages:

vpython 7.6.1
swift-sim 0.8.1
roboticstoolbox-python 0.9.1

When I try to run the example code(the code is from the official release of the robotics-toolbox-python-0.9.1 package :

#!/usr/bin/env python
"""
@author Micah Huth
"""

import roboticstoolbox as rtb
import time
from roboticstoolbox.backends import VPython

env = VPython.VPython()  # lgtm [py/call-to-non-callable]
env.launch()

#  PUMA560
puma = rtb.models.DH.Puma560()
env.add(puma)

for i in range(1000):
    env.step(puma)
    time.sleep(0.1)

I got the following error:

runfile('F:/code/robotics-toolbox-python-0.9.1/examples/VPython.py', wdir='F:/code/robotics-toolbox-python-0.9.1/examples')
Traceback (most recent call last):

  File "F:\code\robotics-toolbox-python-0.9.1\examples\VPython.py", line 10, in <module>
    env = VPython.VPython()  # lgtm [py/call-to-non-callable]

AttributeError: type object 'VPython' has no attribute 'VPython'

Any idea how to fix this issue?
Thanks.

[asmwarrior]

OK, problem is solved by change the line to:

env = VPython()

[asmwarrior]

There is another issue I see:

In [1]: runfile('F:/code/robotics-toolbox-python-0.9.1/examples/VPython.py', wdir='F:/code/robotics-toolbox-python-0.9.1/examples')
Traceback (most recent call last):

  File "F:\code\robotics-toolbox-python-0.9.1\examples\VPython.py", line 18, in <module>
    env.step(puma)

  File "E:\download\sci\Winpython64-3.8.8.0\WPy64-3880\python-3.8.8.amd64\lib\site-packages\roboticstoolbox\backends\VPython\VPython.py", line 215, in step
    sleep(dt)

TypeError: an integer is required (got type Puma560)

The line is: env.step(puma).

I think some interface is changed, but this example code is not updated yet.

[asmwarrior]

I uninstall all the pipy version of the three packages:

robotics-toolbox-python
spatialmath-python
swift

And install all the github versions, this removes a lot of errors when I try to run the codes in example folder. (To use swift-sim under Windows, I have to use a patch here: jhavl/swift#4 (comment) )

Now, I still see some errors:

When run the file: \robotics-toolbox-python\roboticstoolbox\examples\vpython-puma.py, I get such error:

In [1]: runfile('E:/code/robotics/robotics-toolbox-python/roboticstoolbox/examples/vpython-puma.py', wdir='E:/code/robotics/robotics-toolbox-python/roboticstoolbox/examples')
Traceback (most recent call last):

  File "E:\code\robotics\robotics-toolbox-python\roboticstoolbox\examples\vpython-puma.py", line 22, in <module>
    env.step(0.1)

  File "e:\code\robotics\robotics-toolbox-python\roboticstoolbox\backends\VPython\VPython.py", line 204, in step
    graphical_dh_robot.fkine_and_set(q)

  File "e:\code\robotics\robotics-toolbox-python\roboticstoolbox\backends\VPython\graphicalrobot.py", line 802, in fkine_and_set
    poses = self.robot.fkine_all(joint_angles)

  File "e:\code\robotics\robotics-toolbox-python\roboticstoolbox\robot\DHRobot.py", line 902, in fkine_all
    Tall.append(Tj)

  File "e:\code\robotics\spatialmath-python\spatialmath\baseposelist.py", line 368, in append
    raise ValueError("can't append a multivalued instance - use extend")

ValueError: can't append a multivalued instance - use extend


In [2]: 

Any ideas how to fix this issue?
Thanks.

[asmwarrior]

Another issue I see when I use the github version of the "robotics-toolbox-python, spatialmath-python, swift" is that when I try to run a minimal code in the home page:

import roboticstoolbox as rp

panda = rp.models.Panda()
panda.plot(q=panda.qr)

Now, I get such error:

In [1]: runfile('E:/code/robotics/robotics-toolbox-python/roboticstoolbox/examples/mytest.py', wdir='E:/code/robotics/robotics-toolbox-python/roboticstoolbox/examples')
Traceback (most recent call last):

  File "E:\code\robotics\robotics-toolbox-python\roboticstoolbox\examples\mytest.py", line 4, in <module>
    panda.plot(q=panda.qr)

  File "e:\code\robotics\robotics-toolbox-python\roboticstoolbox\robot\Robot.py", line 1151, in plot
    env = self._get_graphical_backend(backend)

  File "e:\code\robotics\robotics-toolbox-python\roboticstoolbox\robot\Robot.py", line 1050, in _get_graphical_backend
    from roboticstoolbox.backends.Swift import Swift

ModuleNotFoundError: No module named 'roboticstoolbox.backends.Swift'


In [2]: 

[asmwarrior]

Now, I still see some errors:

When run the file: \robotics-toolbox-python\roboticstoolbox\examples\vpython-puma.py, I get such error:

In [1]: runfile('E:/code/robotics/robotics-toolbox-python/roboticstoolbox/examples/vpython-puma.py', wdir='E:/code/robotics/robotics-toolbox-python/roboticstoolbox/examples')
Traceback (most recent call last):

  File "E:\code\robotics\robotics-toolbox-python\roboticstoolbox\examples\vpython-puma.py", line 22, in <module>
    env.step(0.1)

  File "e:\code\robotics\robotics-toolbox-python\roboticstoolbox\backends\VPython\VPython.py", line 204, in step
    graphical_dh_robot.fkine_and_set(q)

  File "e:\code\robotics\robotics-toolbox-python\roboticstoolbox\backends\VPython\graphicalrobot.py", line 802, in fkine_and_set
    poses = self.robot.fkine_all(joint_angles)

  File "e:\code\robotics\robotics-toolbox-python\roboticstoolbox\robot\DHRobot.py", line 902, in fkine_all
    Tall.append(Tj)

  File "e:\code\robotics\spatialmath-python\spatialmath\baseposelist.py", line 368, in append
    raise ValueError("can't append a multivalued instance - use extend")

ValueError: can't append a multivalued instance - use extend


In [2]: 

Any ideas how to fix this issue?
Thanks.

I just debugged this problem, and I notice that some times,

robotics-toolbox-python/roboticstoolbox/robot/DHRobot.py

Line 846 in 5468a89

def fkine_all(self, q=None, old=True):

In this function, the Tj = self._base, I see that the _base is an array, not a single SE(3), so to solve this issue, I have such changes:

 roboticstoolbox/robot/DHRobot.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/roboticstoolbox/robot/DHRobot.py b/roboticstoolbox/robot/DHRobot.py
index 96fff873..34ef6dc5 100644
--- a/roboticstoolbox/robot/DHRobot.py
+++ b/roboticstoolbox/robot/DHRobot.py
@@ -882,7 +882,7 @@ class DHRobot(Robot):
         q = self._getq(q)
 
         if self._base is not None:
-            Tj = self._base
+            Tj = self._base[0]
         else:
             Tj = SE3()
         first = True

Now, which the above changes, the crash issue is gone. But I still don't know why the _base is an array.

Here is the test code for this issue:

import roboticstoolbox as rtb
import time

from roboticstoolbox.backends.VPython import VPython

env = VPython()

env.launch()


#  PANDA
panda = rtb.models.DH.Panda()
env.add(panda)

time.sleep(3)
env.step(id = panda, q = panda.qr, dt = 0.1)

time.sleep(3)
env.step(id = panda, q = panda.qz, dt = 0.1)

The code is mainly based from the file: robotics-toolbox-python\roboticstoolbox\examples\vpython-puma.py, but should change some codes, such as rp should be replaced by rtb.

[micah-huth]

Hey, sorry I'm a bit behind in getting to this.

I uninstall all the pipy version of the three packages:

robotics-toolbox-python
spatialmath-python
swift

And install all the github versions, this removes a lot of errors when I try to run the codes in example folder. (To use swift-sim under Windows, I have to use a patch here: jhavl/swift#4 (comment) )

Now, I still see some errors:

When run the file: \robotics-toolbox-python\roboticstoolbox\examples\vpython-puma.py, I get such error:

In [1]: runfile('E:/code/robotics/robotics-toolbox-python/roboticstoolbox/examples/vpython-puma.py', wdir='E:/code/robotics/robotics-toolbox-python/roboticstoolbox/examples')
Traceback (most recent call last):

  File "E:\code\robotics\robotics-toolbox-python\roboticstoolbox\examples\vpython-puma.py", line 22, in <module>
    env.step(0.1)

  File "e:\code\robotics\robotics-toolbox-python\roboticstoolbox\backends\VPython\VPython.py", line 204, in step
    graphical_dh_robot.fkine_and_set(q)

  File "e:\code\robotics\robotics-toolbox-python\roboticstoolbox\backends\VPython\graphicalrobot.py", line 802, in fkine_and_set
    poses = self.robot.fkine_all(joint_angles)

  File "e:\code\robotics\robotics-toolbox-python\roboticstoolbox\robot\DHRobot.py", line 902, in fkine_all
    Tall.append(Tj)

  File "e:\code\robotics\spatialmath-python\spatialmath\baseposelist.py", line 368, in append
    raise ValueError("can't append a multivalued instance - use extend")

ValueError: can't append a multivalued instance - use extend


In [2]: 

Any ideas how to fix this issue?
Thanks.

In relation to this, I tested the code in the presumed commit stage you were at (based upon time of report, I also got the same error), and at the latest stage as of this reply. It has since been fixed since your report, as the latest commit executes without error.

Another issue I see when I use the github version of the "robotics-toolbox-python, spatialmath-python, swift" is that when I try to run a minimal code in the home page:

import roboticstoolbox as rp

panda = rp.models.Panda()
panda.plot(q=panda.qr)

Now, I get such error:

In [1]: runfile('E:/code/robotics/robotics-toolbox-python/roboticstoolbox/examples/mytest.py', wdir='E:/code/robotics/robotics-toolbox-python/roboticstoolbox/examples')
Traceback (most recent call last):

  File "E:\code\robotics\robotics-toolbox-python\roboticstoolbox\examples\mytest.py", line 4, in <module>
    panda.plot(q=panda.qr)

  File "e:\code\robotics\robotics-toolbox-python\roboticstoolbox\robot\Robot.py", line 1151, in plot
    env = self._get_graphical_backend(backend)

  File "e:\code\robotics\robotics-toolbox-python\roboticstoolbox\robot\Robot.py", line 1050, in _get_graphical_backend
    from roboticstoolbox.backends.Swift import Swift

ModuleNotFoundError: No module named 'roboticstoolbox.backends.Swift'


In [2]: 

This error is not VPython specific. When no backend is supplied, the default is used depending on the application (currently: pyplot for DH robots, pyplot2 for ERobots2, Swift for everything else). As you are using the ERobot version of Panda, it will try to launch in Swift.

jhavl/swift#4 (comment)
As for this issue, I'm guessing this is no longer an issue, as you have posted these error reports above?

[asmwarrior]

Another issue I see when I use the github version of the "robotics-toolbox-python, spatialmath-python, swift" is that when I try to run a minimal code in the home page:

import roboticstoolbox as rp

panda = rp.models.Panda()
panda.plot(q=panda.qr)

Now, I get such error:

In [1]: runfile('E:/code/robotics/robotics-toolbox-python/roboticstoolbox/examples/mytest.py', wdir='E:/code/robotics/robotics-toolbox-python/roboticstoolbox/examples')
Traceback (most recent call last):

  File "E:\code\robotics\robotics-toolbox-python\roboticstoolbox\examples\mytest.py", line 4, in <module>
    panda.plot(q=panda.qr)

  File "e:\code\robotics\robotics-toolbox-python\roboticstoolbox\robot\Robot.py", line 1151, in plot
    env = self._get_graphical_backend(backend)

  File "e:\code\robotics\robotics-toolbox-python\roboticstoolbox\robot\Robot.py", line 1050, in _get_graphical_backend
    from roboticstoolbox.backends.Swift import Swift

ModuleNotFoundError: No module named 'roboticstoolbox.backends.Swift'


In [2]: 

This error is not VPython specific. When no backend is supplied, the default is used depending on the application (currently: pyplot for DH robots, pyplot2 for ERobots2, Swift for everything else). As you are using the ERobot version of Panda, it will try to launch in Swift.

jhavl/swift#4 (comment)
As for this issue, I'm guessing this is no longer an issue, as you have posted these error reports above?

See my post here: jhavl/swift#4 (comment)
There are still some code need to be fixed in the robotics toolbox.

[asmwarrior]

Hey, sorry I'm a bit behind in getting to this.

I uninstall all the pipy version of the three packages:

robotics-toolbox-python
spatialmath-python
swift

And install all the github versions, this removes a lot of errors when I try to run the codes in example folder. (To use swift-sim under Windows, I have to use a patch here: jhavl/swift#4 (comment) )
Now, I still see some errors:
When run the file: \robotics-toolbox-python\roboticstoolbox\examples\vpython-puma.py, I get such error:

In [1]: runfile('E:/code/robotics/robotics-toolbox-python/roboticstoolbox/examples/vpython-puma.py', wdir='E:/code/robotics/robotics-toolbox-python/roboticstoolbox/examples')
Traceback (most recent call last):

  File "E:\code\robotics\robotics-toolbox-python\roboticstoolbox\examples\vpython-puma.py", line 22, in <module>
    env.step(0.1)

  File "e:\code\robotics\robotics-toolbox-python\roboticstoolbox\backends\VPython\VPython.py", line 204, in step
    graphical_dh_robot.fkine_and_set(q)

  File "e:\code\robotics\robotics-toolbox-python\roboticstoolbox\backends\VPython\graphicalrobot.py", line 802, in fkine_and_set
    poses = self.robot.fkine_all(joint_angles)

  File "e:\code\robotics\robotics-toolbox-python\roboticstoolbox\robot\DHRobot.py", line 902, in fkine_all
    Tall.append(Tj)

  File "e:\code\robotics\spatialmath-python\spatialmath\baseposelist.py", line 368, in append
    raise ValueError("can't append a multivalued instance - use extend")

ValueError: can't append a multivalued instance - use extend


In [2]: 

Any ideas how to fix this issue?
Thanks.

In relation to this, I tested the code in the presumed commit stage you were at (based upon time of report, I also got the same error), and at the latest stage as of this reply. It has since been fixed since your report, as the latest commit executes without error.

When I revert my local change of this:

diff --git a/roboticstoolbox/robot/DHRobot.py b/roboticstoolbox/robot/DHRobot.py
index 133f1712..55f38515 100644
--- a/roboticstoolbox/robot/DHRobot.py
+++ b/roboticstoolbox/robot/DHRobot.py
@@ -979,7 +979,7 @@ class DHRobot(Robot):
         q = self._getq(q)
 
         if self._base is not None:
-            Tj = self._base
+            Tj = self._base[0]
         else:
             Tj = SE3()
         first = True

try to run a simplified examples/vpython-puma.py file:

import roboticstoolbox as rtb
import time

from roboticstoolbox.backends.VPython import VPython

env = VPython()

env.launch()

panda = rtb.models.DH.Panda()
env.add(panda)

time.sleep(3)
env.step(id = panda, q = panda.qr, dt = 0.1)

time.sleep(3)
env.step(id = panda, q = panda.qz, dt = 0.1)

I don't see the error again, so I guess it was fixed in github master.

In-fact, I set a breakpoint in the line: Tj = self._base in my above diff file(in line 983 in DHRobot.py), and I see it never get reached this breakpoint, I'm not sure which commit fixed this issue.

Thanks.

[micah-huth]

Closing this VPython issue thread, as the VPython issue(s) have been fixed.