How to throw error and exit with a custom message in python

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.x
print("fatal error", file=sys.stderr) # Python 3.x

The 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")

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.

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