How to Make a Simple Calculator With Python | Python Beginner Projects

hello and welcome back to the channel this will be video 4 in our python tutorial series so if you missed the first few on installing and setting up python and pycharm initial introductions to variables and getting user inputs go ahead and check those out if you're not familiar because we will be continuing from where we left off in this video so for this video we're creating a basic four function calculator and what that means is we're going to be taking three user inputs num1 num2 and operation and so let's get right into it uh first thing we're going to have is a variable which we'll call number one and we're going to have that be an input where we ask the user to enter first number just like that and we want this to be a numerical variable type so if you remember from past videos when you want to make sure variable is going to come in as an integer you go ahead and use int and then the operation we're just going to make that an input where we prompt the user to enter operation and since we need this to be some fairly specific info let's even give them you know plus minus multiply divide give them the options for the operations so they know what we're looking for and then we'll make number two just like the first number of being integer we'll ask for an input and we will say enter second number and you can see already i get kind of uh loosey-goosey with whether i use one parentheses and two parentheses they're identical to python so it's honestly sort of whichever one i click at the time so it's not it's good to be consistent but i'm also trying to show you can use either of these and it'll be just the same so right now if we run this it shouldn't do anything but it should take our three prompts and you can actually see we can even enter things that aren't those correct operations in here but then the code doesn't do anything so that's what we'll be doing next we have three variables that are now gathering operator info but we haven't used it to do anything and before we haven't done anything conditional where we check what a variable actually is and do specific specific functionality based off of what was entered so that's going to be handled in something called an if statement and again if you're familiar with any general coding concepts this shouldn't be too new to you but in general an if statement is going to check that a variable in this case our operator is equal to a specific thing so first we're going to handle the addition case and an important thing to note in python is you need to double equal signs if you're checking equivalency single equals sign is going to tell the code you want to set a value to that variable double equals sign is a comparison checker and then if statements as well as four and while loops and things we'll cover in future videos they need to end end with a colon so they know where the end of the conditional statement is and this is our first introduction to indentation in python this is very important when you put code underneath a conditional statement it goes in by one indentation so if you were to put another if statement inside of that and then conditions inside that it's going to be another level of indentation down that's how visually that's how python knows what code is contained in what modules so for now if operation is equal to addition then what we want to do is print the value of number one added to number two and we're going to go ahead and take that and we're going to copy that down as we handle our next condition if the operation is subtraction then we're going to do number one minus number two and this code actually will work and it is valid but something that's kind of cool you can do inside python as well is an l if and this code can only be executed if this code did not run so for the case of looking for a specific operation it doesn't make that much sense but let's say we were checking for a name and we want to say if operation if name equals peter print your name is peter we would use an l if your name was pete you would print out pete but because you wouldn't want to see that p was in the name but not the whole name that's a little bit of a complicated explanation but it'll come in handy later just something to start thinking about so we'll go ahead and copy this in two more times we'll handle the multiplication and division scenarios and we should be able now i'm sure it'll show up if i'm in there we should be able to now say five plus three and right there you can see it gives us eight before finishing the routine so let's try a few other functions let's try nine times two and it looks like uh oh of course because i left them all as subtraction when i copied them let's go ahead and run nine times two again because it should not be seven i'm not great at math but i knew that one so there we go 9 times 2 is 18 but you're gonna notice a few of the issues in our calculator that we can actually go ahead and take care of right here if you want to enter a number that's a decimal right now because obviously we're not always going to be dealing with whole numbers we get an error because we're saying we expect an integer so here's our introduction to the second type of python variable that handles numbers rather than the int function we're going to use what's the float function meaning floating point decimal value so we're going to change both of our numbers to floats and what you'll immediately see is it accepts values like 5.4 we can do addition and we can give it 1.2 and it's going to go ahead and return for us 6.6 in quite a few decimal places i'm actually fascinated at where that 5 comes from but that's so the float is what lets you handle things more precise than integers so we should be able to go ahead and say 5.6 let's subtract from it ah 1.9 and there you go it's it's running math and uh it's adding some decimals which is neat but you can see right there we're getting decimal values and then one other limitation that we're going to find is if we say well the first number is 56 the operation is you know three and you accidentally put a number in there we're not handling that anyway it just thinks it's running the code but it's also not doing anything we can actually handle this situation by adding some code up here that says else and this is saying we've checked and our operation is none of these four things and we can go ahead and give them a conditional that says operation entered was invalid so all we're doing here is we're saying you know what we checked it's not addition multiplication subtraction or division we went through and it's none of those so that means your operation is invalid so if we run this now let's say we want 12 and we want we accidentally added a name and we want to add it to 2 operation entered was invalid there you have that right there and that's pretty cool we've built a basic calculator that handles four functions as well as lets you know whether or not you've got a valid operator so as always thanks for tuning in hope you enjoyed the video feel free to leave a comment if you have any questions i'll try to clarify anything for you and be sure to like and subscribe if you found this content useful and be on the lookout for more tutorials coming soon thanks bye