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Welcome to the day 11 of the 100 days of hell with python algo trading today we will be understanding encapsulation which is one of the most misunderstood concept of object oriented programming why because many of us knows only the bookish definition but no one knows why we really need encapsulation so today we will be understanding what and why of the encapsulation completely so so without a further Ado let’s get started so first of all let’s understand the bookish definition of encapsulation so encapsulation is a key principle of object oriented programming that bundles data that is attributes or variables and methods which is functions operating on the data into a single unit or class it restricts direct access to some components preventing accidental interference and misuse means we have a class in which we have attributes and methods correct the variables and functions so we can say in order to prevent misuse and accidental interference right so now let’s see some key aspects and benefits of encapsulation so the first one is data hiding which is true right after this explanation we will be understanding these old concepts with the help of an example the real life example so it will be much better for all of us to understand this in deep right so the first benefit or you can say the key aspect of encapsulation is the data hiding in internal details are hidden from the outside world using access modifiers which are private protected and public correct the next is public interface so with the help of encapsulation we can provide controlled access to data through well- defined public methods we will understand that also for now you just understand that with the help of encapsulation we can hide our important data and we can prevent the misuse or we can say The Accidental interface right second is.
We can provide a public interface through which we can provide only the authorized data to the outside world right the next is modularity right so in which what we can do we can make our objects self-contained and that also helps in the understanding right and also in maintenance and debugging if we are having any error so with the help of encapsulation we can directly point that at which location in our code we are having the issue the next is abstraction which means like the program can be very complex from inside but what is the end goal of a programmer or a company the end goal is to provide the best solution to the user right so they do not have to check the complexity or anything they will just get a simple interface and through which they can only access the authorized data right the next is maintainability so it is T here the system is easier to maintain and extend since each component is self-contained and interacts through well defined interfaces which means that like once we have written our application and after that that we want to modify the code so it becomes so easier because we just have to modify like a single piece of information or we know exactly that what we want to modify so it becomes so easy to maintain with the help of encapsulation or we can say object oriented programming so that was the theory part of encapsulation now let’s quickly move to the examples and let’s see so before diving in the encapsulation example let me quickly show you one very small concept that is instance variable so what are the instance variable for example we have a class trading bot and inside that we have a function or you can say we have a method Constructor method right or you can say Constructor function so inside that we have three parameters the self the name the initial cache so here.
We know that the self is the object itself then we are left with only two parameters so let me quickly create an object of this class so what I’ll do I’ll just go ahead and write let’s say bot one bot one is equals to trading bot and a parenthesis inside that we will provide the name so let’s say name is Apple and we have initial cach so it can be 1,000 USD right so now we know that while creating this object we have passed two arguments one is the name of the stock and another is the initial cache right so if I want to access this name again what I will do I’ll write bot one. name correct so it will print out the apple right if I write bot one dot cache it will give me an output of 1,000 until now you are clear right so we can say this bot one dot name is the instance variable of this class again this bot one. cach is another instance variable of this class that is okay right but if I create another object let’s say with the name bot two and what I’ll do I’ll okay let me remove this dot not required here and what I’ll do I’ll write as a trading bot and here I can give let’s say Microsoft msft and initial cach is 2,000 so now if I want to access this name variable so what I have to write I have to write like B 2. name and it will give me an output of msft correct similarly for bot 2. cach it will give me 2,000 so what I’m trying to show you here that we can have multiple instance variables for example this this was the first instance variable correct this is the second instance variable means for a single class we can have multiple instance variable so whenever we create an object and we pass the arguments a new instance variable will be created but for the normal variables we can hold only one value right so at a time we can hold only one value in a in a variable but in instance variable we can hold multiple values so that is a difference between a variable and an instance variable and in the previous session.
We have understood what are the reference variables right so you just need to have a clear understanding of what is a reference variable what is an instance variable and what are the variables so that was a simple concept so now what we can do we will quickly visualize this instance variable in the python tutor and then we will proceed with the example of uh encapsulation now we quickly move to the python tutor and I will paste the code here so what is happening here we have a class right and here we have two objects of that class so first is B one inside that we have the stock as apple and the initial cash is 1,000 and in second instance the second uh object we have the stroke as Microsoft and the amount is 2,000 so before that what we will do we will create instance variable so bot one do name do cache again let me quickly copy and paste this here so here I’ll just change to B two so now we can see we have a class then we have two objects and then we have two instance variables of each object so when I click on uh visualize so it will take me to this screen and here we can see that we have 15 Steps so let’s understand this one by one so when I click on the next button it will take me directly to the object creation code so here we can see that a new frame is created that is a global frame and inside that we have the uh trading board class as an object and you can see here it has been created okay so now The Interpreter is at the object creation line so here when I click on next you can see here that an instance of the class has been created with the arguments name and initial cache here the value is Apple and thousand is the cash and self also is there correct that is the trading board instance so now again the interpret goes to the inside the class and here we are at the Constructor function correct so when I click on next and it will like assign these values to the self Lo name it assigned the apple and for the cash it assigned the th000 right then when.
We click on next it will go to the second object similarly it will perform the same steps and again it will go inside the class and it will execute the Constructor function with without calling right so when I click on next it will perform the same steps so first the name and then we have cash and in return there is none right so we have already understood that when there is no return value but still the function returns and that is none right so now when I click on next it will take me to the instance variable so here what one do name so when I click next so now the program goes to the instance variable so when I click on next it doesn’t print out anything why because we have to add the print function here so let me quickly go here and I’ll add print here so now let’s click again on the visualize execution and here you can see that when we click next next next next and when we reach to the instant variable here these are printed out Apple again the name and again the cache so here we can say that instance variables can hold multiple values at the same time and likee the normal variable which can hold only one value so this was the uh concept of instance variable and keep that in mind it is very important now let’s start the encapsulation example so so what we will do we will create a trading bot that is capable of executing buy and sell orders based on the threshold value which we provide so let’s start that so first of all so let’s create the class so and let’s give it the name auto trading bot here as usual we will Define the Constructor function So Def in it and inside that we have to pass the self then what we will do the user will provide the threshold value so threshold and here what we can do we can just like assign the variable threshold means the threshold parameter is there and when the user pass it it will become self do threshold you can even change the name there is no interation between this this and this so you can have whatever you want right then what we will do we will create two more attributes so the first is self do position and currently that is none let’s assign the value as none correct and the third is.
We will create an empty list so self dot price data right and let’s keep it empty for now so here we have three attributes the first is threshold second is position and third is price data so what we are doing here the threshold will be provided by the user and for now the initial position is none the price data is not date price data is empty right so these all are inside the Constructor function so as soon as the object is created this function will be executed and these old values will be initialized let me correct this also I have to add another underscore underscore okay now we are fine right until then what we can do we can just test it whether it’s working or not so what we’ll do we’ll create an object below so let’s say I’ll create Autobot one is equals to auto trading bot and then we will provide the threshold value so let’s say threshold is 100 correct and when I hit shift enter it runs perfectly fine and in the next cell what I’ll do I’ll try to access the variables inside so so when I click on dot it shows me some suggestions which are the price data the position and threshold the price data is currently an empty list and in position the currently is none and threshold we have already provided which is 100 so if I try to access the price data and when I hit shift enter it gives me an empty list similarly if I try to access the autobot Autobot dot let’s say position and when I hit shift enter it gives me nothing right because this is a none value we have assigned and then we have the last one which is threshold which we have already provided so when I shift enter we get 100 so it’s working fine so far correct so let’s proceed again so now let’s move to the next part so what we will do here we will create the skeleton of this class so what we can do our main object here is to so now our main goal is to analyze the current market and then execute the trades based on the current data so in order to achieve that what.
We need to do we need to fetch the data from the market then we need to fetch the latest data then we need to evaluate that then we will execute the trade that’s how the flow is so let’s first create the skeleton of the class so what we will do we’ll first fetch the data so fetch Market data a function right we just pass it here and similarly let me copy and paste this go here and I’ll paste all these uh let’s do it one more time so here we have to add the colum again and again right the first is to fetch the market data then we need to fetch the latest price so fetch latest price so I’ll just write here the function name as latest Price latest price right then we need to evaluate so we can change it to evaluate price then we can give another function which is to execute the trade execute trade and last what what we will do we’ll create a run function so with the help of that we’ll be able to control all the above functions right so now now we need to add self also here because as per the object oriented programming we need to add the object here so we’ll add self in all the classes right so that’s the skeleton of this class okay now let’s build the logic before that we can hit shift enter and check that it is working fine it is working fine and here also hit shift enter it’s working fine and when we click like when we just try to check so when I click on dot it should display all the functions so you can see here threshold position evaluate price execute trade fetch latest and price and run so means so far everything is okay so like when you are trying to create big program you can divide that program into smaller chunks and then you can work on small small chunks so it becomes so easy to write the code right so let’s write the code so so what will happen happen here we will get the threshold here so so let’s write the code for the first function so what we can do here.
We’ll first fetch the market data so here in the real life scenario we have to fetch the market data from the with the help of API but here we’ll just for the sake of this example we’ll just simulate the data so I’ll just copy the attribute and I’ll assign some value here in a list so let’s say we have 80 uh 90 100 110 and 120 and 130 right so now this function will return the self do price data so self do price data and then what we can do we can also print that uh Market data has been fetched right fetched so until now it should be very clear let me change these value to the current price of the Bitcoin so let’s say we have 69140 currently and I’ll just copy uh this price and I’ll paste here so uh 2 3 4 5 6 correct and let’s quickly change these values so this is is 1 15 160 170 and 1 80 and 1 190 and what we will do we will also change the threshold value so let’s say we keep the threshold as 69160 so here we’ll change this threshold so when I open the chart so here you can see that these are the bars so 1 2 3 4 5 6 so means in the list we have given these six values right the opening or closing price you can take anyone so for example I’m taking the closing price here latest bar right or we can say the last bar before the current bar so these are six values and these and we will take the closing price so again the example we want to check this value right the the second last bar so we’ll open so let me open uh it again so in the second function what it will do it will check the self do price data is there or not if it is there then it will return the self Dot price data correct else it will return none right so now what we will do we’ll just test these two functions whether it’s working fine or not so I’ll just hit shift enter and here again I’ll pass the argument as the threshold 69160 and now when I click here as dot I can see we have all the functions and.
Watch this Day 11 video tutorial
Day 11: Object-Oriented Programming Part – 3
