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How to Remove Duplicates from List or Array in Python – GATE, Interview & Placement Practice
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Jun 1, 2025
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0:00
uh hello guys welcome to this video so
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in this video I'll show you a very
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common program which is asked inside
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Python interviews competitive
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programming placements as well how to
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remove the duplicates from a list of
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numbers so if you have a array or a list
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of numbers if you have duplicate numbers
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in this case you can see two is
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repeating four is also repeating so if
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you want to remove all these duplicates
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number from this list and this will be
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the output which will be given so 1 3 1
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2 3 4 5 we will remove all the
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duplicates so this is our Python program
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i will show you step by step so if I
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just execute this program here app 16
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py you will see list without duplicates
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1 2 3 4 5 so it removed all the numbers
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which are repeating only having one
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instance only so all the duplicates are
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removed so now let me just show you how
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this program is
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executed let me paste in this software
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which will show you step by step how
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this program executes so first of all we
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have a list of numbers so we have this
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array of list of numbers here so you can
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see this is the zeroth index 1 2 3 4 5 6
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so we have six numbers and uh now we
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will loop through for detecting the
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duplicates we need to declare another
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array here unique numbers which will be
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empty by default so this is the empty
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array which will hold the output the
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unique numbers so again for this uh
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logic guys we are using another for loop
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if you are a Python developer for loop
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is the most used concept you will use
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for loops a lot so you just need to
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learn how to write for loops so here we
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are looping through each number in the
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list we are simply saying for number in
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the actual array here which is your
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numbers we are looping through each
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number and here we are checking that if
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the number is not already in the unique
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number and for actually detecting the
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duplicates we we need to have another
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variable here which is a boolean
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parameter is duplicate is set to false
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so by default the value of is duplicate
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is false and now the number is one
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because we are at this number position
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so here we are simply checking in this
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if condition that if the number is equal
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to this number is not present so because
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the unique numbers is currently empty
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this number is not present so this will
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be added to the unique number so we
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simply add this using the append method
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so we add this one to the unique
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number so this is added right here so
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this is unique now we come to the second
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iteration right here which is we are
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number becomes two two is also not
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present right here in this so two will
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also get
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added so you can see
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that two will be added here now we come
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to the third index which is again two so
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now this becomes interesting because two
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is already present so we come to this
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for loop and
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uh so two is not equal to 1 we compare
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it with the first number two is not
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equal to one so this will not be
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executed we come to the second number
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which is two so 2 is equal to two here
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because two is already present so this
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will not be executed and we come out of
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this so this will be executed because
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this will evaluate to true so now this
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variable will become from false to true
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so it's a duplicate number we'll remove
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this we will ignore this we will simply
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break out of this loop and we come to
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the next
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number so now we come to the next number
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which is three three again is not a
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duplicate it's not present so again it
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will get added then we have four four is
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also not duplicate so it will get
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added then we have again four so four is
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a duplicate number
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so so you compare it 1 2 3 and then the
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last index which is four is equal to
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four so it's a duplicate number so this
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will not be added so then lastly we come
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to the fifth number fifth is a not a
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duplicate it's a unique so it will get
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added so that's all after that it will
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print out this list without duplicates 1
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2 3 4 5 so hopefully you have understood
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this program very simple program we run
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a simple for loop and then we have the
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out inner for loop for checking whether
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the number is unique or not if it is
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unique then we add this if it is a
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duplicate then we break out of the loop
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and ignore it so in this way you can
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write this program and uh also check out
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my website guys free media tools.com uh
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which contains thousands of tools
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