Shallow Copy Vs Deep Copy in Python

Key Takeaways

hello all my name is krishnak and welcome to my youtube channel so guys we are going to continue the advanced series of python and here we are going to see the exact difference between shallow copy versus deep copy so in this particular video i'm going to take three things that we are going to learn one is equal to then one is copy operation and then one is something called as deep copy operation so we'll try to understand this particular difference i had a lot of confusion before on this but i try to learn it i try to understand it and there were some of the queries that were asked by some of the people in one of my classes at that time i just tried to dig dive into it and try to understand the entire concept and the same concept i'm going to explain it over here to you all now remember whenever you want to learn about shallow copy or deep copy always consider the data that you are going to or the variables that you are going to initialize should be collection because collections of elements are mutable and they should also have this mutability property itself right and if you don't know about mutability don't worry i'll also be uploading a video very soon about that also now let's take one example and let's understand first going i will go ahead and understand about this equal to operation now suppose if i want to apply a list one i will create a list one considering some elements like list one is equal to one two three four and then i will also create another list which will be assigned to list one now this equal to operation i'm talking about this list2 is basically assigned with list one now once i execute this here you will be able to see this is my list one and then you'll also be able to see this is my list two okay so list one is this list two is this now what happens suppose i try to uh take out one element of list two suppose i want to take out the index element of list two and when i check the index one i'm getting the value as two suppose i assign it with some other value like one okay and i execute it now what will happen is that i will be able to see that in list two i'll be getting that particular element in the second in the first index as thousand now one important thing that you have to note that even though i check the element of list one here also it has got updated now why probably this thing may have happened because understand list one when it is creating this collection of items it has been creating in some memory location and both the variables are actually referring that but same memory location so that is the reason if one of the variable changes the element it will also get reflected in the memory itself so both the variable will be referring to the same memory itself right so this is the most important thing and this is what you have understood about equal to before going ahead with respect to this particular video this video has been sponsored by an academy so guys if you are in the final year of a graduation or 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our copy operation now see this i'm just going to say copy operation now inside this copy operation what i'm going to do instead of just assigning like list one i will do dot copy operation okay i'll do something called as dot copy okay now when i do dot copy that basically means it says that okay i'm going to take all the elements of list one and remember guys this is a kind of shallow copy okay this is a kind of shallow copy i'll tell you the exact difference between shallow and deep copy but just understand when we are taking this shallow copy as an example we have to use dot copy operation now when we do use dot copy operation you here you will be able to see once i'll execute it okay suppose this is my list 2 and if i try to see this particular elements and suppose i want to assign i want to change any elements over here suppose i want to change the first index element right so what is my first index element 2 let me just consider that i want to make it to thousand now when i do this particular operation remember when i do dot copy operation here it is going to make a different memory location it is not going to just refer the same memory location okay now if i go and see my list two and if i try to compare with list one you'll be seeing that sorry it should be lst one you'll be seeing that in list two only your first index has been changed but in list one it has not been changed because now both are having different different memory location now this is one thing this is one very very important thing now guys if i create some list or i can say if i create some nested list this shallow copy definition whatever we did over here will change a little bit let me just show you an example again i'm going to take a shallow copy with respect to nested list okay this will be with respect to nested list and suppose let me consider and create some nested sub list okay so something like this 5 6 7 8 and then i will just create this and now if i go and see this here you is your list one so this is basically your list one and here you can actually see your list two right so i have my list one and list two now just consider over here one very very important thing definitely whenever i use nested sub list okay over here initially i just created this list right it was a single dimension list i can consider in that way i did not had a nested list over here but here when i created this nested list sub nested list or nested list at that time you'll be able to see that if i try to change one element like this suppose if i say list of one list of one is nothing but this one and suppose if i go and see zero this basically referring to the five element if i try to see this value i'm getting five now if i try to replace this with something else like hundred okay because here you'll be able to understand the exact difference between shallow copy and deep copy now if i go and see my list 2 here you'll be able to see that 100 is getting replaced 100 is getting assigned if i also go and see my list 1 here also you'll be able to see 100 is getting a sign now what is happening over here initially when you used like this in this particular way when i was trying to change only one single element inside a list that is basically an item right this is one item this is the other item this is the next item and this is the next item here we have this i can consider as one item right and this i can consider my next item inside this item you have different different objects right when you have in this particular scenario and when you try to change this particular value this value will get copied in both the list after you make the changes because it is referring to the same object inside the nested list both the variables are referring to the same object that is present inside the list this is the most important thing to understand okay in this scenario whenever you have a nested list and when you try to perform the same operation like how we did with respect to one specific element inside this nested list at that time those updation will happen if i take one more example suppose this is my list one right the if i'd write dot append when i do a dot append operation see this this is very very important in shallow copy if i do a dot append operation with some of the elements like 2 comma 3 comma 4 comma 5 and if i execute it now if i go and see my list 1 here you'll be able to see that i'm getting this particular element but since i've used this shallow copy over here if i go and see in list 2 here you will not be seeing that this value is getting appended so this item will not get copied but if you are making changes inside and um suppose if you are changing if you are if you are making changes on the object that is present inside the list at that time it will definitely make a change understand guys very very simple is that when i'm creating a nested list this is considered as a collection of item okay inside this i have various objects right one two three four right this will be getting referred by both list one and list two but when we have multiple items like this and when i'm adding suppose one item like two three four five at that time the same thing is not getting referred over here this is about shallow copy i'll talk about deep copy also now let's go ahead with respect to deep copy now in deep copy you try to do anything and for using deep copy i have to use import copy and inside this import copy what i'm going to do is that i'm going to first of all create a list one suppose this is my list one one comma two comma three comma four okay and list two is basically i'll just assign it to um i can use this copy library i'll say copy dot there's something called as deep copy and here i'm going to use list one now when i execute this okay suppose this is my list two and i want to change probably the first index element is equal to thousand here you will be able to always equal to 100 and now if you go and see your list two here you are getting hundred but when i go and see list one i'm not getting any value this works exactly like uh shallow copy in this scenario when you have a single nest a single uh list itself a single dimension list where you don't have nested list right this is not a listed list whenever this scenario is there remember deep copy in this scenario in this scenario i'll just write down a comment in a single dimension list when when i say single dimension don't over complicate it things guys it is not a nested list i'm just saying that so i'll say that in a normal list okay shallow copy is equal to deep copy okay now let's try to understand what happens if i try to make a nested list suppose this is my list one and here i'm going to take elements like this okay and here i'm going to say 1 2 3 or comma 3 comma 4 comma 5 and then i'll have one more list like 5 comma six comma seven okay now see this if i make list two and here i'll say that copy dot deep copy dot deep copy copy dot deep copy this is very very important to understand you'll face some kind of confusion i'd suggest go and just practice this here you'll be able to understand now see this this is my list 2 okay this is my list 2 right now when i am using list2 suppose i want to change one element one of zero at that time if i go and see this i'm getting three suppose if i change this element to hundred okay this is the element guys okay now if i go and see my lst2 and if i go and see my lst1 here you'll be able to see that now this copy is not being this value is not getting copied in the other list since we performed this only operation in list two this got only copied over here this is basically deep copy now for everything that we do a separate memory location is basically getting created this is the difference between shallow copy and deep copy guys in this case shallow copy is not equal to deep copy because it is creating a different memory location so i hope you understood this guys this is the basic difference understand if i try to perform with the help of shallow copy my shallow copy will be something like this see instead of using this deep copy i'll be using um i'll just say that list one dot copy so this is basically shallow copy okay and if i try to perform this operation again like this it will not work see here i'm getting 100 and if i go and see list one again i'm getting hundred but if i do with deep copy then here you'll be able to see that only list two element will get updated list one will not get updated so just try to have a look on to this particular notebook i've discussed three things equal to copy and deep copy operation and i hope you like this particular video please do subscribe the channel if you're not already subscribe i'll see you on the next video have a great day thank you and all bye