Python Programming Tutorial #17 - Optional Parameters

hey guys and welcome back to another YouTube video this is the 17th video in my Python programming series and today we're going to be talking about functions more advanced functions and something called optional parameters so let's just give a quick refresher of what a function is I'm just going to write one very quickly I did do another video on basic function so if you haven't seen that yet go check that one out first now here we've defined what we're going to call the function func and then inside of these brackets we put something called parameters if you remember that from the other video so in this case I'm just going to put X as my only parameter and then I'm simply going to print X to the screen just like that so a very very basic function but it's just to give you a quick refresher of what it does now when we wanted to call our function all we had to do was write our function name and then put a brackets or the brackets like this and then inside of our brackets if we had a parameter set we had to do we had to give it that parameter so we could do three we could do hello let's just do hello in this case and we'll click f5 and we get hello on the screen just like that now we can change this again to maybe Tim which is my name just like that and we get to M printed the screen very basic very easy just like that okay so that's pretty much what a function is now what we're going to talk about today is more in-depth on these parameters so you remember we could give it multiple parameters so we do X we could do maybe text like this so we had X and text and we could print X to the screen and maybe we'll say if text is equal to UM let's say 1 so with a string 1 then maybe we'll print text is 1 otherwise so else we will print text is not 1 just like that very easy ok so now what we have to do when we call the function is we have to give it another parameter in this case I'm going to give it 2 and we'll see what happens we get Tim and then texture I misspelled that my bad is not 1 now if I change this parameter to 1 again we'll see that we get text is 1 now again that's just another example but in some cases when we call a function and we have many parameters and maybe we don't have many but we don't want to constantly be rewriting these parameters we want to have something called the default value for our parameters so X maybe we always want to give our function the value of X but in text here we always want it to be set to something unless we otherwise specify so in this case I'm going to say text and then the equal sign I'm going to put two just like that now here I'm going to remove the one and you'll see what will happen here we'll just run it to show you and then we'll go in what's actually happening so we get Tim and then text is not one so what actually happened here is since I didn't specify a value for text so I didn't do a comma and write something else here it defaulted to the value of two now we can prove that by just simply printing out text and showing you that it is actually two so we have Tim and two just like that if I wanted to change this value now all I would have to do is simply put a comma here in the function and change it to whatever I want so in this case I'll do 67 and if we print it again you'll see we get 67 so that's how the optional parameter works now all you have to do to set an optional parameter is simply type an equal sign after your parameter so if I have X and I'll set it equal to three like that now when I call the function I actually don't have to give it any parameters because it already has the optional parameter of three and of two which are going to be the default values if I don't write anything in my function argument here so inside of these brackets and you'll see you again we get three and two because those are the default values now there is one tricky thing that you have to understand about these optional parameters say you wanted to have X stay at the default value so you want it to be three and you didn't want to type three in the brackets like that but you wanted to change the text optional parameter - something like seven or eight or maybe another string well you can't actually do that in order to change this text optional parameter you would have to also set a value for X here so if I try to I'll say I just want to set the text to three so I'll do like three here it's actually not going to change I'm sorry and what do you call it isn't I'll change it something else so we can see it better - five let's do five it's actually not going to change that second variable right it's going to change the first one automatically because that's just the order in which they're defined so if you wanna if you have more than one optional parameter you will have to set a value for the one before in order to change the one afterwards like this so that's the only tricky part about these optional parameters other than that they're extremely useful again you would use them if you're constantly using a function and you don't want to have to keep writing in parameters you only want to give it a parameter in a very specific case then you would have that optional parameter already set so you don't have to keep typing a certain word you don't have to keep giving it a value like that so this has been a shorter video but this is the video on how to do an optional parameter they look just like this they're very simple and pretty basic and I hope you learned something today if you did please like and subscribe I will see you again in another video