Answers for "how to raise a error in python"

throwing an exception python

raise Exception("message")

raise exception in python

raise Exception('I know Python!') # Don't! If you catch, likely to hide bugs.

python raise TypeError

def prefill(n,v):
    try:
        n = int(n)
    except ValueError:
        raise TypeError("{0} is invalid".format(n))
    else:
        return [v] * n

python raise error exit

# 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")

python: raise error

class MyError(TypeError):
    pass

raise MyError('An error happened')