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Python Program to Find Second Largest Number in a List Tutorial For Beginners
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Jun 1, 2025
Get the full source code of application here:
View Video Transcript
0:00
uh hello guys uh welcome to this video
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so in this video I will show you a
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Python program which will able to find
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out the second largest number in a list
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uh it's a question that is asked in many
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interviews and competitive programming
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so I basically show you step by step
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here so I'm using this software python
0:22
twitter.com which actually shows the
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live uh step-by-step visualization of
0:27
the code so this is my program here so
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let me just uh run this step by step so
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first of all this function which is
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second largest function is initialized
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here as you can see it is expecting a
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list of numbers so we have this list of
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numbers right here 12
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451 31 10 so this is a list of numbers
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we are targeting now in the next step
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whenever this list is initialized as you
0:55
can see now the list is initialized
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these are a set of numbers in which we
1:00
need to find out the second largest
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number so now we go to the next step so
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this function is initialized as you can
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see we are there on this step right here
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so this function is
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initialized and now we come to the next
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step so here we are simply checking that
1:18
if the length of the list is smaller
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than two in this case it is not smaller
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than two so now this condition will
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evaluate we go to the next step and here
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we initialize two variables guys which
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is largest and second both will be
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negative infinity so we are initializing
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both these variables to negative
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infinity which is essentially we are
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putting it to a smaller number so this
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can be zero as well but we are putting
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it negative infinity
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so after that we come to the we are
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simply using this for loop here so we
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are on the first element in the for loop
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so the value is 12 here so the num value
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is 12 now we have the logic here if I
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come to the next step we are simply
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having if this if condition that if the
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number that you are targeting is smaller
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than or greater than largest so largest
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as you can see it's put to negative
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infinity so it must be larger so this
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condition will evaluate to true and we
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come to this next step so we actually
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store this second largest number we
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initialize it so this second largest
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number
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becomes to in negative infinity so now
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in the next step we are putting this
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largest number which we have found at
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this moment of time it is 12 so we will
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make this largest to be 12 so in the
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next step largest will become 12 and now
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the cursor will move to the next element
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in the array which will be 45 so now
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again we will check in this if condition
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that if 45 is is greater than 12 because
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up till now the largest number is 12 so
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now in the next step 45 is greater than
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12 so now this will actually make the
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second
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largest
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number so the second largest number will
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become 12 so now if I go to the next
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step you will see now we have number
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45 so second largest will become 12 here
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as you can see and now the largest
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number will
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become 45 because 45 is greater than 12
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so now this will be stored in the
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largest variable so this is the logic
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here as you can see now we come to the
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next step next number in the list which
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is two so two is again is not greater
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than 45 as you can see largest value is
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45 so this will evaluate to false
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so now we need to find out the second
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largest number here so we have this else
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if condition right here so here we are
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checking that if this number which is 2
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is uh greater than
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12 so we are checking it for the second
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largest number so this this condition
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also evaluates to false so we come to
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the next element in the array we move to
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the next element so now the number value
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become 41 so we come to this number in
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the list again 41 is not the largest
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number so our largest number is 45 so 41
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is not greater than 45 so this condition
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will evaluate to false and this then now
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the second condition here just look at
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this condition so now 41 is greater than
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12 this is our second largest number but
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now this 41 is greater than 12
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and 45 is not equal to 41 is not equal
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to 45 so now this needs to be the second
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largest number so now we need to update
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this second variable so now we come to
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this step so now second variable second
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largest number become now
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41 so now we come to the next number in
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the list which is
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31 so now number becomes 31 so 31 is not
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greater than
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45 so this condition will evaluate to
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false and 31 is also not the second
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largest number as it's not greater than
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41 so this also evaluates to false we
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come to the last element in the list
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which is 10 so this will also evaluates
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to false in both the conditions
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and
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now the for loop will
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end as you can see it is end and uh now
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we'll simply return the second largest
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number which is 41 from this function so
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return value is
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41 and then we simply print out the
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second largest number is 41 so this is
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essentially the program guys uh we
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define this
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function hopefully you understood this
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condition
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so thank you very much guys for watching
6:28
this
6:30
video and also check out my website
6:34
freemediattools.com
6:36
uh which contains thousands of tools