How to throw error and exit with a custom message in python
Calling sys.exit with a string will work. The docs mention this use explicitly:
In particular, sys.exit("some error message") is a quick way to exit a program when an error occurs.
There are 3 approaches, the first as lvc mentioned is using sys.exit
sys.exit('My error message')The second way is using print, print can write almost anything including an error message
print >>sys.stderr, "fatal error" # Python 2.xprint("fatal error", file=sys.stderr) # Python 3.xThe third way is to rise an exception which I don't like because it can be try-catch
raise SystemExit('error in code want to exit')it can be ignored like this
try: raise SystemExit('error in code want to exit')except: print("program is still open")
I know this is an old thread, however you can also raise an error like this:
raise SystemExit('Error: 3 processes cannot run simultaneously.')
One advantage of this approach is that you don't have to import the Python sys module. This works on Linux with Python 3 and Python 2. I have not tested it on Windows or Mac OS.