Selection Sort Algorithm Explained (Full Code Included) - Python Algorithms Series for Beginners

Continuing the Python algorithm series with Selection Sort. Check out the full playlist here:

The Selection Sort Algorithm starts by setting the first item in an unsorted list as the position with the lowest (minimum) value. We then use this to compare each of the items to the right. Whenever we find a new item with a lower value, that becomes our new minimum value and we continue on.

After one iteration of the selection sort algorithm, we create two sublists. One will be for unsorted items and the other will be for sorted ones. We move the minimum item from the unsorted sublist into the last position of our sorted sublist.

After we finish all the iterations, we should be left with only the largest number in our unsorted sublist (which is now sorted to the highest position as it is the highest value.)

The selection sort algorithm has a complexity of O(n^2) still but nearly always outperforms the bubble sort algorithm in situations where writing is important (fewer switches, more efficient per iteration).

If you had any questions about the selection sort algorithm, or any of the other algorithms in this series - please let me know in the comments below!

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#Python #Algorithm #SelectionSort
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Full code from the video:
def selection_sort(list_a):
indexing_length = range(0, len(list_a)-1)

for i in indexing_length:
min_value = i

for j in range(i+1, len(list_a)):
if list_a[j] #less than list_a[min_value]: #"angled brackets not allowed in youtube description"
min_value = j

if min_value != i:
list_a[min_value], list_a[i] = list_a[i], list_a[min_value]

return list_a

print(selection_sort([7,8,9,8,7,6,5,6,7,8,9,0]))

Packages (& Versions) used in this video:
Python 3.7
Atom Text Editor

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Code from this tutorial and all my others can be found on my GitHub:

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[janmuhammad]

I wish I have teachers like him at my college

[lovesignal]

Yeah, you're really talented at teaching. Believe me when I say you've got a real gift. And thank you for sharing it because you don't know how daunting this concept was to me when hearing it from other instructors.

[abhivaryakumar]

4 years later and you are literally saving my life
Such a gift for teaching
Thank you

[utkarshmalik]

Hey Derrick this is the best Algorithm Playlist I ever came across
So please it's a humble request to make more videos on Algorithm

[navodyaliyanage]

this is absolutely the best series on algorithms, I struggled a lot watching other videos, but this is really amazing, clear and short.

[AlfredDHull]

Still loving this video two years later Derrick!

[andrewbrower]

This tutorial is incredible. Thank you for teaching it so effectively

[RadioKilledMusic]

def selection_sort(list_a):


for i in indexing_length:
min_value=i
for j in range(i+1, len(list_a)):
if list_a[j]<list_a[min_value]:
min_value=j

list_a[min_value], list_a[i]=list_a[i], list_a[min_value]
return list_a


more efficient code, last if in j loop is not necessary

[johnhillescobar]

This is a great, amazing and super instructional video. My code for this algorithm is by far more complex. Love the code you created.

[coolios]

Dude!!! Derrick this is so awesome. you make these concepts so easy to learn. Keep it up!!!

[easynow]

i have to admit.. I love your short but badass bass music at the intro..

[abletmuhtar]

Pls teach all of those fundamental algorithms. Thanks

[timohelasvuo]

Here again for another alogorithm treat! Thanks buddy for yet again great video. Looking forward to look into the code on my comp later today

[shrutikanikhar]

You're an amazing videos are very helpful.... Thanks

[tuborao]

Hi Derrick, first of all I would like to thank you for your videos. They are helping me a lot!
I think I found an indentation error inside your script in your githup area.
The "if min_value !=1" is not indented with the "for j", and this can cause some sort errors if the first element of the list is equal to the last element.
thanks!





for j in range(i+1, len(list_a)):

if list_a[j] < list_a[min_value]:

min_value = j




if min_value != i:

list_a[min_value], list_a[i] = list_a[i], list_a[min_value]




return list_a




print(selection_sort([6, 7, 8, 7, 6, 5, 4, 5, 6, 7, 6, 7, 8, 9, 7, 9, 0]))

[AlternateMelatonin]

I always wonder, why my professor spends 50 mins lecture just to teach what you show in 5 mins. Thank you always.

[mahadkhurram]

Thanks bro, I have an exam tomorrow. And this is really gonna help.

[rushas]

I like the new intro and the outro! Content is also great!

[lone.wof]

Great tutorial! Easy to grasp the concepts.. Subbed!

[aqualung]

Your videos as terrific, thank you. Below is what I came up with - it is almost twice as fast as your code. Why is that??

def
sorted_list = []
while len(unsorted_list) > 0:
min_index, min = 0, unsorted_list[0]
for i in range(0, (len(unsorted_list) - 1)):
if unsorted_list[i] < min:
min_index, min = i, unsorted_list[i]

return sorted_list