Julia Tutorial - 10. Exception Handling

Key Takeaways

hello everybody let's talk about exceptions in Julia programming language today exceptions are errors detected at the time of program execution for example if you try to concatenate string with a number using plus operator it will give you this error this is a load error exception another one is you're trying to find out the square root of a negative number and you know that's not defined so it will give you this domain error so this is another the exceptions so if you go to uh Julia l.org website uh it has a list of all these exceptions okay so we just looked at domain error the problem with this exceptions is that if you are running uh your code and if this accept H happens it will terminate the execution of the code so sometimes this might be disastrous you what you want to do instead is whenever acception occurs you want to handle it and gracefully uh take like a detour you know let's say you are driving on a road and you find an accident you don't terminate driving right right you take a detour so exception handling is sort of like taking a detour and finding an alternate path uh in your program execution so here I'm going to show you how you can use TR catch to uh handle this square root exception for that you can write try oops I hit alter enter by mistake uh sqrd catch exception occur so the code that you suspect might throw an exception you have to enclose that into this try catch block and here in catch you'll write a code that you want to execute upon uh exception occurrence so this is short of like a you're taking a D2 and this is n so due to this what will happen is your program will not terminate it will continue execution even Beyond this point okay so if I execute this it will say exception occurred okay now here what I did is I handled all kind of exceptions into this generic block sometimes you may want to know the type of exception and for that you can specify your exception object here so when you say catch y your exception is stored in this y object and you can print that here so if I hit alter enter it says domain error so the type of exception that occurred was a domain error okay now sometimes you don't know what kind of exception will happen so you want to make a check on it and what I'm going to do here is I will throw two kind of exceptions so here I have an array and what I'm doing here is finding the square root of second element of this array okay now possible exception that may happen here is domain error if any of these elements is less than minus one if this is minus one then it will result into a domain error but let's say if I do something like index array out of bound then it will throw me this error bounds error right so uh if you want to do a specific check on type of exception you can use is a function you can say if is a your exception object domain error if the type of exception that is thrown is domain error then you can just say domain error domain error else if the type of exception is bounce error then you will say okay this one is Bounce error okay and I forgot and so let's execute this so now it is saying bounce error based on this type check if I do two and try to find square root ofus this one it will go through this one so now it hit this one previously it was hitting this line so this this is how you can check the type of exception and based on the time you can do necessary handling I'm just using print allent right now but but in the real world code you would have you will have a real code uh return to handle the type of exception okay now sometimes uh uh you may want to throw your own exception uh you probably don't want to use this system generated exception in that case you can use a throw statement so here let's say if I have this kind of code I'm just throwing the exception straight away but but you might have some custom function return or custom logic where certain conditions cannot be handled in which you will throw uh exception so for this you will use a throw statement and in the bracket you can uh specify what type of exception you want to throw so here I'm using domain error again we looked at Julia website and we have all these exceptions so you can throw any of these or you can have generic exception object as well again when I execute this it is saying domain error okay so that was a sweet uh like short and sweet introduction on uh exception thanks for watching