使用os.system时是否有办法捕获RuntimeErrors？

Question

I'm writing a tool that sends commands to the CMD for Google Lighthouse and want to catch the error if an URL isn't valid. What exception would I use?

I'm currently trying to catch RuntimeError in the Exception when entering an invalid URL.

try:
    os.system("lighthouse --quiet {} {} {} {} {} --output-path={}/{}.html ".format(DevEmuStr,throttlingVar,CacheStr,presetVar,url,reportlocation,filename))
except RuntimeError:
    print("Please provide a proper URL")

Instead of "Please provide a proper URL" I still get:

Runtime error encountered: The URL you have provided appears to be invalid.
LHError: INVALID_URL
at lighthouse (C:\Users\sugar\AppData\Roaming\npm\node_modules\lighthouse\lighthouse-core\index.js:44:11)
at chromeP.then._ (C:\Users\sugar\AppData\Roaming\npm\node_modules\lighthouse\lighthouse-cli\run.js:182:12)
at process._tickCallback (internal/process/next_tick.js:68:7)

And Lighthouse just continues with the next URL

Is there another error I could catch?

Answer 1

Thanks to everyone that tried to help me, I finally found a way to get it.

By adding this:

lh_url_ok = os.system("lighthouse --quiet {} {} {} {} {} --output-path={}/{}.html ".format(DevEmuStr,throttlingVar,CacheStr,presetVar,url,reportlocation,filename))
if lh_url_ok >0:
    print("Error")

i was able to check if the exit code was above 0 (0=no error)

Answer 2

No, there isn't an exception you could catch from Python.

It appears to me that "Runtime error encountered" is output printed out by lighthouse, it isn't an actual Python exception you could catch.

Python doesn't know anything about what is internally going on in the executable you start with os.system, you can just get the output and an exit code.