Python for SPIKE Prime (LEGO 45678) Part 6: Turns with Functions ***For version 2 (Legacy)***

Key Takeaways

hello welcome to another episode of python for spike prime today we're going to learn about using functions to make your robot do really accurate turns hello my name is gary and today we are going to look at uh using function so it's going to be a little bit more complicated than the previous episodes so if you haven't already then check out the previous episodes over here today we're going to look at defining functions which in scratch equates to something like my blocks my blocks are really useful in scratch because it lets you repeat things that you um you don't want to have to retype or or copy a lot of times so functions are really really important for programming in general let's jump right in first of all let's um open up spike prime start a new project uh call it ca python functions and then hit the python icon click create we'll hide the helper okay so here we are importing all our classes then we create objects and then we run the code so here let's do some hints just for our own reference because there's going to be a bit of a change later on first thing we want to do is define our motors so uh let's change it up a bit let's call it wheels equals motor pair c d remember um these objects we can call them whatever we want so um wheels motor movement motors they're all they're all fine as long as you keep consistent all through your code and then the way that we use the the gyro to turn on a robot is that we use a um the internal gyro on the spike prime hub there's no separate gyro sensor for spike prime uh it's all built into the hub and the um the the sensor is called a motion sensor inside the python language when we want to turn a certain angle for example if we want to turn the robot 90 degrees a lot of people who start off with with coding with lego um get get confused they use the move degrees command so they might do something like um [Music] say i want a moving degree so let's go wheels dot move and then let's go like 90 degrees right that looks looks correct but it's actually not because um when you put in 90 degrees like that the degrees is actually the amount that the wheels are rotating okay so if the wheels rotate 90 degrees it's like a quarter of a rotation and that's not going to be enough to turn your robot all the way around to 90 degrees so uh it's a little bit uh a bit tricky for for new programmers to understand that that the 90 degrees on the movement wheels uh only change the degrees of the movement not the actual whole angle of the robot does that make sense in order to do that we need to do this so we go while hub dot motion sensor um dot get your angle is less than 90 then so this is a while loop and we're doing we're repeating something until the your angle is no longer less than 90 degrees what are we repeating we're repeating the wheels movement wheels dot start a hundred so when you go start then the value in here is a steering value remember it defaults at 0 which is a straight move but 100 is turned towards the right and negative 100 is turned towards the left and then when we reach um 90 degrees then what do we want to do wheels don't stop okay super simple but there's a there was a lot to unpack in there right let's uh connect our robot and try to get it working okay right connected let's run the code and see if we do a 90 degree turn cool so that works it was a little bit quick so let's change the speed down a little bit wheels that set default speed to say 20. all right but now what if i wanted to repeat right hand turns throughout my code i don't want to have to copy this out all the time so now we're going to create a function so to create a function the proper way to do it would be to do it after you create objects but before you execute the code so here we write down functions and to define a function we use the def keyword so def we'll define define right turn open and close brackets and then column and then here this is where we define the function and then now we're going to copy well cut all this code out and then paste it in here but we've got to make sure that everything is indented to be under the right hand turn function this wheel start has to be indented under the while loop okay so the indentations in python are really important because it tells the code what the scope is okay so now now that we've defined the function for a right turn we've got to call the function so down here where we had the code before we just go right turn open and close bracket okay let's run the code [Music] perfect what if i tried to run the code twice if i wanted to run the code twice then you'd think that i'd go like this right turn right turn again but you're going to find that something strange is going to happen so then you did the turn once and the reason is because when you start the code it resets the gyro um and then it doesn't reset the gyro after you've made the turn so it's a good thing we have a function because now we're going to use the function to reset the gyro before we do the maneuver okay so let's have a look at this so here we want to reset the gyro before the start of moving on our turn so we're going to define our function again we go hub.motionsensor dot reset your angle okay so now it should be fine and do the two moves instead of just the one [Music] okay perfect so that's how we do a right-hand turn but what if i want to do a custom angle term just like in scratch we can add parameters to our my blocks right and here we add parameters to our functions arguments so um we're going to add a um a parameter in so that you can change what degrees you want to turn the robot [Music] here we go so we don't have to worry about the right hand turns and we can keep our function there because you know you might want to do a right-hand turn like that so let's go define custom turn and then here we put an angle angle is a um is a is a um a variable that we create right that's this could be named anything it could be x for example but um here we're going to call it angle and then everything is going to be exactly the same as what we had before except this 90 instead of 90 we're going to replace that with angle so now if i wanted to do a custom turn then i would say like if i want to do a 45 degree turn then i'd go custom turn 45 okay [Music] okay isn't that cool all right that was a really uh super simple short and um also quite complex uh lesson so i hope you enjoyed it please like and subscribe if it's helping you out and i will see you again on the next one bye you