Importing python3 library

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Hello,

I want to use some libraries that are python3 based to run on a pynq board with pynq overlay which is python3 based. The goal is to read the sensors from a 10 DOF IMU.

One one side, I have the following python script:

import time
from pynq.overlays.base import BaseOverlay
from pynq.lib.pmod import Grove_IMU
from pynq.lib.pmod import PMOD_GROVE_G3

base = BaseOverlay("base.bit")
mb_info = {'ip_name':'iop_pmoda/mb_bram_ctrl' ,'rst_name':'mb_iop_pmoda_reset'}
gr_pin = PMOD_GROVE_G3  # SDA on 3, SCL on 7 (PMOD A): https://pynq.readthedocs.io/en/v2.0/pynq_libraries/grove.html
imu = Grove_IMU(mb_info, gr_pin)
imu.reset()

SampleFreq=30
delay=1/SampleFreq

while True:
    accl = imu.get_accl()
    print("Accelerator: ", accl)
    mag = imu.get_compass()
    print("Magnetometer: ", mag)
    gyro = imu.get_gyro()
    print("Gyroscope: ", gyro, "\n")
    time.sleep(delay)

To launch this python script, I have to do it with $ sudo python3.6 imu_reader.py. There it is the first problem, that it needs sudo.

From the ROS side, I have the following custom messages (I know I could have used directly sensor_msgs/Point32) and python script:

sensor.msg:

float32 x
float32 y
float32 z

imu_data.msg:

imu_sensors/sensor accelerator
imu_sensors/sensor gyroscope
imu_sensors/sensor magnetometer

imu.py

#!/usr/bin/env python
import rospy
from imu_sensors.msg import sensor
from imu_sensors.msg import imu_data

def imu_loop():
    pub = rospy.Publisher('IMU_output', imu_data, queue_size=10)
    rospy.init_node('talker', anonymous=True)
    rate = rospy.Rate(2) # 10hz
    imu = imu_data()
    num = 0
    while not rospy.is_shutdown():
        #hello_str = "hello world %s" % rospy.get_time()
        #rospy.loginfo(hello_str)
        #pub.publish(hello_str)
        num = num + 1
        if num>251:
            num=0
        #for i in range(5):
        #    vec.array[i] = num

        imu.accelerator.x = 1
        pub.publish(imu)
        rate.sleep()

if __name__ == '__main__':
    try:
        imu_loop()
    except rospy.ROSInterruptException:
        pass

Now I have a problem to incorporate the first python script into ROS. First of all, I am following this tutorial to compile ROS with python3 support. It basically does the following:

## Prerequisits:
### 1. Install basic Python3 packages and some ROS dependencies (there might be more depending on each ROS package)
```
$ sudo apt-get install python-catkin-tools python3-dev python3-numpy
$ pip install pyaml
$ pip install rospkg
$ pip install numpy
$ pip install empy
$ pip install cffi
```

### 2. Install Python virtualenv
```
$ sudo pip install virtualenv
```

## Procedure
### 1. Create a virtual environment (workspace) and activate it
```
$ mkdir -p ~/python3_ws/src
$ cd ~/python3_ws/src
$ virtualenv py3venv --python=python3
$ source ~/python3_ws/py3venv/bin/activate
```

### 2. Install ROS packages required by your ROS code
This is needed when you need some off-the-shelf packages which have to be re-compiled for python3

### 3. Create your ROS package and compile with the specific flag
```
catkin_make -DPYTHON_EXECUTABLE:FILEPATH=/home/xilinx/python3_ws/py3venv/bin/python
```

Like this, I am able to compile the ROS python script and I can see that it publishes on the expected topic. The pynq libraries are in the /home/user folder so I added this path to my PYTHONPATH. I only added from pynq.overlays.base import BaseOverlay, recompiled and run it with rosrun imu_sensors imu_pynq.py. However, as expected, it ... (more)