raise statement on a conditional expression

If you absolutely want to raise in an expression, you could do

def raiser(ex): raise ex

return <value> if <bool> else raiser(<exception>)

This "tries" to return the return value of raiser(), which would be None, if there was no unconditional raise in the function.

Inline/ternary if is an expression, not a statement. Your attempt means "if bool, return value, else return the result of raise expression" - which is nonsense of course, because raise exception is itself a statement not an expression.

There's no way to do this inline, and you shouldn't want to. Do it explicitly:

if not bool:
    raise MyException
return value