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So in the previous session we have seen that how we can make our data private but if we still want to access we can easily access right which made me more depressed that why we can’t do that because in the other languages like Java and C C++ we can do that right we can make our data fully private and nobody can access no matter what happens but in Python we can access so while researching I found one single line on stake overflow and which made me smile and I’m sure that when you listen this you will also which says python is made for adults python is made for 18 plus That’s why nothing is truly private in Python because as we have seen previously that python is so flexible that it doesn’t restrict you completely for anything you have the option to make your data private but if someone from your company is still trying to access that then that is a problem of your company culture not pythons right that’s why we have the option but we also have the flexibility to access in case if sometime it is required so that was oneliner now let’s move to the next topic which is getter and Setter method so let me share my screen so when we make our data private python automatically converts that to a different name so here you can see it was underscore class name then double underscore and the then attribute name but even after that you can access the attribute but you cannot make changes to the private variable so so that was the explanation now let’s understand one more thing understand the getter and Setter method so let me open the terminal you can see here.
We have made all these attributes as private and I cannot access with just like uh let me run this and at here the name is B 3 dot if I write at threshold then it says if I write like the class name so auto trading B so Auto when I hit shift enter we get the value and with the help of this we can even change the value let’s see if I make it 70,000 so the value will be changed and when I again access this it will show me modified threshold we can say that we have the flexibility but we have the drawback also right so in order to resolve this issue we can use getter and seter Method so let me quickly first explain you what are the getter and seter methods so let’s start the example of getter and seter Method so what we will do here we’ll just take this code and paste it here okay so when I hit shift enter and I try to access the data from here so let’s say I’ll create another object with the name b for and I’ll give the class name with the threshold value so let’s say it’s 70k and now when I add another cell here and try to access the attributes from inside I can see that position price data and threshold is still visible but if I try to access done already I’ll add the class name here so Auto uh trading bot and hit enter and it will return me the uh threshold value and we don’t want to give the direct access to the data to any other person so what we will do here we’ll use another method that is geta Method so so what I’ll do I’ll just write here Define get I’ll give here any name so let’s say what it will do it will just return the threshold value right so it.
Will return the return and self dot yeah so now I hit shift enter and so now when I try to access this uh I’ll write bot 4 Dot and now when I try to access this so what I’ll write bot four dot and here in the suggestion you can see we have another method which is get attribute and I’ll select this close the parenthesis and now actually we don’t want this for now so I’ll just remove this so I’ll just remove and I’ll again shift enter And now when I run this we can see that it is returning us the value of the threshold so with the help of this geta method we can easily avoid giving the access to the to our data we can give a method with the help of that method they can access the data and they can use it so now let’s say I want to change the value of this I want to modify so what I’ll do I’ll set another method here and we can name it as set attribute and here self and we can say uh modified threshold so or new threshold so here what it will do it will just will return the self dot this one so now let’s try to access this so I’ll just hit shift enter and here I’ll take another cell and I’ll write both for DOT so here we can see the set attribute also so here I will change the value from uh 7,000 to 8,000 or 80 when I hit shift enter it is returning us the 80,000 and if I check here now it has changed to 0k right this is how you can use the getter and seter Method and this is the safest way to give the access of your private data if the person wanted what he could have done he would have just changed this to string and when we hit shift enter and when we try to access this and after that if I have more functionalities like the execution or or the comparison then definitely it will not be able to do that because this is a string so in order to avoid that what you can do.
We can add a conditional statement here so if new threshold so the type of new threshold is equal to equal to Str Str then it will perform this action otherwise if we try to be over smart what it will return don’t try to be over smart right and now when we hit shift enter it says expected yes it expected here so now when we try to access this so I’ll just hit shift enter and it still return returns me the string so what we can do I’ll just change it to a string of course and now when I try to change so now now let’s say if the junior programmer wants to make it a string so what it will be return don’t try to be or smart and if you’re working fine let’s say giving the right value it will work fine when we give the right value here so let’s say 8,000 we have to change it to int if the junior programmer now give any other value than integer it will be displayed as don’t try to be over smart let’s say if he’s giving correct value 8,000 then it will be working fine so this is the example of get attribute and set attribute and it will be very useful for you to make your code more safe now we have collection of objects so in this what we can do let me take this example again trading b or I’ll paste it here and here what I’ll do I’ll just change these values let’s say it was the threshold and we can also give the name like the stock name so uh let’s say stock name and here stock name let’s say stock name and I’ll remove this one okay so we have two parameters the first is stock name and second is threshold I hit shift enter and then if I try to uh create object of this class so what I’ll do I’ll I’ll create here so let’s say I’ll create Capital bot one is equals to auto trading bot and here we will provide two values the first is the stock name so let’s say I’ll give apple and threshold we can provide is let’s say 1 1 0 we can also have bot 2 which is again equals to auto trading B and here we can provide let’s say Microsoft uh we can give 1 15 correct and let’s take uh two more value so I’ll just copy and paste this again and I will I’ll quickly change here Bard 3 B 4 and Apple 2 BTC and Microsoft 2 ethereum so now what we are doing here.
We have created four objects right so when I H shift enter so now as we have seen already so many times that in Python all the data types like integer string and this class functions all are objects right so I’ll add these in inside the list so bot one then bot two and Bot 3 and Bot 4 and if you can imagine this is very powerful now we can treat the class objects as as a normal data type right list on these we can perform dictionary we can perform any operations which we can do on other data types so let’s say bot one and if I want to apply for Loop so for I NL print I and when I hit shift enter all the objects will be printed out this is really powerful right now if I want to access these values what we can do we can give the class name then the attribute name but let’s just for the sake of Simplicity what we’ll do we just make it a normal attribute for now but make sure you make a habit that whenever you are creating the class and inside that you make all the data private always Stoke name or threshold name so what I’ll do here I’ll just give I do threshold and now when I hit shift enter all the threshold is printed out and if I want I can also print I do stock name right and with this you can imagine the possibility you can perform with python means there is no limit sky is a limit you can do whatever you want with the python just your Basics needs to be very strong if your fundamentals are strong then you are the Unstoppable then again if we can make list then of course we can make dictionary also right so what we can do here uh let’s say we have this I’ll go here and I’ll type D and here what I can do instead of this I’ll change to the curly bres correct and here I’ll give like P1 and P2 P3 and P4 correct it says P1 is not defined actually we have to make this a string so P1 and P2 P3 and P4 so now I H shift enter we can use the for Loop so for i n d and print so if I want to print the values from the dictionary what we can do we can write like the stock name so when I hit shift enter it will print all the stock names and if I want the uh threshold so you can do that also shift enter and all the threshold will be printed out so now.
We are able to like the normal data type and we can perform all the operations right so now we have again one very very important concept which is static variable so as we have seen that all these are instance variables because see and the self. stock name is also an instant variable because whenever we create the object it gets executed and we can get the value but what if I want some uh variables for example example in a trading strategy or in a trading application we want to count the we want to count the trade number like we have a trade ID if I want to apply that counter that how many trades are being happened here so whenever we make an object of this so let’s say I’ll create a counter here so self counter uh plus equals to and here I’ll give the value the initial value so we can give it as self Dot or in the starting we can give it so now let’s say.
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Day 12: Object-Oriented Programming Part – 4
