Python program throwing error when called through subprocess

Question

I have a simple python file myfile.py:

#!/usr/bin/python

def on_message(ws, message):
    if message == 'pong':
       pong = True
       receiver_exists = True

def on_error(ws, error):
    print("### error ###", error)

def on_close(ws):
    print("### closed ###")

def on_open(ws):
    print('### connected ###')
   

if __name__ == "__main__":

import websocket
import _thread as thread
import time
import re
from camera import VideoCamera
from deviceSpecificVals import machineSerial, token
    while True:
        try:
            uri = f"ws://myurl/stream/{machineSerial}/?{token}"
            ws = websocket.WebSocketApp(uri,
                              on_open = on_open,
                              on_message = on_message,
                              on_error = on_error,
                              on_close = on_close)

            ws.run_forever()
        except:
            pass

When I run this by simply executing it from the terminal it works as expected. When I try to run this from another python program using: os.system('myfile.py') or subprocess.Popen(['myfile.py'], stdin=subprocess.PIPE)

Both will throw the error ImportError: No module named websocket

Why does it work fine from terminal but not using os.system or subprocess

do you run it in terminal - myfile.py or python myfile.py? Do you have other Pythons installed? Do you have this problem when you run /usr/bin/python myfile.py? Maybe it runs with other Python. maybe you should use different shebang in code - ie #!/usr/bin/python3 ? You could add code which display information about used Python, current working dictionary, etc. — furas
– furas, Commented May 12, 2021 at 2:15
Change this to answer and I will mark it as such. The shebang (python3) did it, good catch — MattG
– MattG, Commented May 12, 2021 at 9:42

furas · Accepted Answer · 2021-05-12 09:48:17Z

2

Sometimes computers may have two (or more) Pythons installed (especially Linux/Unix) and it may need correct shebang to run it with expected version

#!/usr/bin/python3

or

#!/usr/bin/python3.8

To run also with version installed in virtual environment

#!/usr/bin/env  python3

answered May 12, 2021 at 9:48

furas

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