Binary Trees in Python: Introduction and Traversal Algorithms

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In this video, we will go over the binary tree data structure. We then go over how to implement this data structure in Python. We then cover the three recursive depth-first search traversal algorithms (preorder, inorder, and postorder) and implement those recursively in Python.
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[@LucidProgramming]

Note that @26:30 I call the "inorder" traversal function inside of the "postorder" traversal function and neglected to change it to postorder. This was a copy-paste error. You can fix it by changing the "inorder" call in postorder to the appropriate postorder call. Sorry for the mistake, and thanks for watching!

[@Soccercrazyigboman]

How can you go from child back to parent if you don't have a next and previous pointer?

[@Soccercrazyigboman]

By next and previous I should say if each node doesnt have a pointer pointing to the one above it as well as to the one below it?

[@AshwaniKumar-dj6re]

@@Soccercrazyigboman he is using recursion

[@NicholasSilva1380]

That changes the expected output from 4-2-5-6-3-7-1- to 4-5-2-6-7-3-1-

[@violetkimani3118]

Hi, would be more efficient to add a function from within the class for adding values to the tree? does it help/ would it be more efficient especially during interviews

[@bijayamanandhar3890]

Thank you for the great tutorial! I am a new developer still looking for a job after graduation from a boot camp. I never had a chance to learn the data-structure, dfs, bfs etc before. Now, it's getting clear to me step by step after watching the videos you posted.

[@LucidProgramming]

Thank you! If you like my content, I've been working on some projects during the past couple of months. If you would like to stay up-to-date, please consider subscribing to my mail list. Also, if you haven't already, please consider subscribing! I really appreciate the support, and if you want to support the channel, I do have a PayPal link paypal.me/VincentRusso1 for donations that go directly to the creation of content on this channel. I hope that the content I provide there will enhance the videos on my KZbin page. bit.ly/lp_email

[@turjo119]

I was stuck for hours trying to understand this, you made it so simple! Thank you so much

[@LucidProgramming]

Cheers! If you enjoyed and benefited from my content, please consider liking the video and subscribing to the channel for more content like this. If you would like to support the content creation on this channel please consider unblocking ads when watching my videos as this is how I support my time to make content. I hope to be putting out more similar videos soon!

[@turjo119]

@@LucidProgramming Done and done my good man!

[@LucidProgramming]

@@turjo119 Cheers, thank you!

[@edgarlip2]

wow - it is awesome !!! i can tell one analogy that helped me a lot : when do i collect the value : • pre-order - when value collected ?: once I am hovering on a node I am collecting it's value. • in-order - when value collected ?: if the node has no left node or the left node is already visited then add this value. • post-order - when value collected ?: once the node has no left nor right or left and right has been already visited then I will collect the value. HTH

[@LucidProgramming]

Thanks, and yes that's a great way to remember them!

[@safderaree]

Hands down the best explanation, I've struggled for so long trying to get the intuition through my textbook. Thanks!

[@LucidProgramming]

Thank you! If you like my content, I've been working on some projects during the past couple of months. If you would like to stay up-to-date, please consider subscribing to my mail list. Also, if you haven't already, please consider subscribing! I really appreciate the support. I hope that the content I provide there will enhance the videos on my KZbin page. bit.ly/lp_email

[@safderaree]

@@LucidProgramming Sure, I've subscribed and signed up for the mailing list. You've made my interviewing process so much smoother.

[@LucidProgramming]

@@safderaree Awesome, that's really great to hear! :)

[@muhammadsalisabdulsalam4016]

This is the most simplified video tutorial with good examples, the best I have seen so far. I got everything after watching this video only once. A lot of online tutorials are just too ambiguous and really confusing. Lucid you're the best for sure. Thanks a lot

[@LucidProgramming]

Thank you! If you like my content, I've been working on some projects during the past couple of months. If you would like to stay up-to-date, please consider subscribing to my mail list. Also, if you haven't already, please consider subscribing! I really appreciate the support, and if you want to support the channel, I do have a PayPal link (www.paypal.me/VincentRusso1) for donations that go directly to the creation of content on this channel. I hope that the content I provide there will enhance the videos on my KZbin page. bit.ly/lp_email

[@muhammadsalisabdulsalam4016]

@@LucidProgramming Sure, I'm interested. But how do I subscribe to your mail list please?

[@LucidProgramming]

@@muhammadsalisabdulsalam4016 Just follow the link here: bit.ly/lp_email :)

[@rhythmsaparia8788]

Your explanation to data structure concepts in python is THE best!

[@LucidProgramming]

Thank you! If you like my content, I've been working on some projects during the past couple of months. If you would like to stay up-to-date, please consider subscribing to my mail list. Also, if you haven't already, please consider subscribing! I really appreciate the support, and if you want to support the channel, I do have a PayPal link (www.paypal.me/VincentRusso1) for donations that go directly to the creation of content on this channel. I hope that the content I provide there will enhance the videos on my KZbin page. bit.ly/lp_email

[@CodeX-mhs]

Extremely thankful to you sir.

[@LucidProgramming]

Thank you for the kind words, glad the videos are useful for you!

[@CodeX-mhs]

@@LucidProgramming A very welcome sir. Please keep providing. The growth doesn’t justify ur quality. Keep it up sir.

[@enkaibi2756]

Too excited to sleep now! I finally understand it! Best video on Traversal Algorithms explanation! Consider watching all your python video!

[@LucidProgramming]

Thank you! If you like my content, I've been working on some projects during the past couple of months. If you would like to stay up-to-date, please consider subscribing to my mail list. Also, if you haven't already, please consider subscribing! I really appreciate the support, and if you want to support the channel, I do have a PayPal link (www.paypal.me/VincentRusso1) for donations that go directly to the creation of content on this channel. I hope that the content I provide there will enhance the videos on my KZbin page. bit.ly/lp_email

[@enkaibi2756]

@@LucidProgramming Just a tiny recommendation, on 17:06, it would be better to use self.root instead of tree .root. Keep going! !!

[@LucidProgramming]

@@enkaibi2756 Point well taken. Thanks for the comment! :)

[@wyllerdesousa1710]

Nice introduction! Thanks to support the TI community.

[@LucidProgramming]

Cheers!

[@TechArtGenius]

The height and depth concept..I think the depth at the root node is depth 0 and increases by 1 as you go down the tree. And this is the opposite for the heights. But looks like you started counting at 1 instead of 0.

[@hassanfarah3501]

God bless you Sir. I have been following your tutorials for a while and you are a LEGEND

[@LucidProgramming]

Thank you! If you like my content, I've been working on some projects during the past couple of months. If you would like to stay up-to-date, please consider subscribing to my mail list. Also, if you haven't already, please consider subscribing! I really appreciate the support, and if you want to support the channel, I do have a PayPal link www.paypal.me/VincentRusso1 for donations that go directly to the creation of content on this channel. I hope that the content I provide there will enhance the videos on my KZbin page. bit.ly/lp_email

[@deojeetsarkar2006]

Your videos deserve more views

[@LucidProgramming]

Thank you! If you like my content, I've been working on some projects during the past couple of months. If you would like to stay up-to-date, please consider subscribing to my mail list. Also, if you haven't already, please consider subscribing! I really appreciate the support, and if you want to support the channel, I do have a PayPal link (www.paypal.me/VincentRusso1) for donations that go directly to the creation of content on this channel. I hope that the content I provide there will enhance the videos on my KZbin page. bit.ly/lp_email

[@ПавелТаранов-э1ч]

Большое спасибо за ваше видео) Это потрясающе, я посмотрел ваш Гайд по связным спискам и теперь я тут. Лучшие видео по этой теме!)

[@dmgisi]

I appreciate the good video and clear explanation. With a little more editing and attention to detail, it can become more polished and will be excellent.

[@LucidProgramming]

Thank you! I hope that the videos on this channel keep getting progressively better. Thanks for watching!

[@nero9985]

Thank god I looked at the comments regarding the issue with the post order function, I spent a good 10 mins looking to see if I had the wrong implementation

[@LucidProgramming]

Glad you caught that, and sorry for the trouble!

[@chrisgoehl2745]

Great Video! Thank you for visualising and really emphasizing on the most basic aspects as this is something which I personally as a Beginner seem to struggle with! Keep up the good work it is really appreciated!

[@LucidProgramming]

Thanks, Chris! That feedback is really helpful for me and I will try to keep that in mind for future videos. Thanks again for watching and for the comment!

[@jethrotalavera3314]

Best video I've seen on this topic. Thank you!

[@LucidProgramming]

Cheers! If you enjoyed and benefited from my content, please consider liking the video and subscribing to the channel for more content like this. If you would like to support the content creation on this channel please consider unblocking ads when watching my videos as this is how I support my time to make content. I hope to be putting out more similar videos soon!

[@bhuwansharmaa]

Best Explanation recursion is bit confusing but following each step through example made it easy... Thanks

[@LucidProgramming]

Awesome, that's great to hear. Thanks for watching!

[@reccartoon]

i really love the way you are explaining all these concepts in very effective manner thanks for this :)

[@LucidProgramming]

Hi Sarfaraz. Really appreciate that comment, that's very much appreciated! Thank you for watching, and I'm happy to hear this video was effective. Cheers!

[@bhaskarbhuyan30]

Very informative and easy-to-understand tutorial. Thank you for this incredible contribution to the enthusiasts and learners!

[@LucidProgramming]

Thank you! If you like my content, I've been working on some projects during the past couple of months. If you would like to stay up-to-date, please consider subscribing to my mail list. Also, if you haven't already, please consider subscribing! I really appreciate the support, and if you want to support the channel, I do have a PayPal link (www.paypal.me/VincentRusso1) for donations that go directly to the creation of content on this channel. I hope that the content I provide there will enhance the videos on my KZbin page. bit.ly/lp_email

[@Unknown_22-z8c]

very good video for those who want to pick the grasp of binary tree quickly

[@LucidProgramming]

Cheers! If you enjoyed and benefited from my content, please consider liking the video and subscribing to the channel for more content like this. If you would like to support the content creation on this channel please consider unblocking ads when watching my videos as this is how I support my time to make content. I hope to be putting out more similar videos soon!

[@wikhan2002]

Awesome! Just Awesome! This is where I could navigate to learn such an important thing earlier.

[@LucidProgramming]

Thank you! :)

[@ilanaizelman3993]

Can't be explained better. Thank you!

[@LucidProgramming]

Cheers! If you enjoyed and benefited from my content, please consider liking the video and subscribing to the channel for more content like this. If you would like to support the content creation on this channel please consider unblocking ads when watching my videos as this is how I support my time to make content. I hope to be putting out more similar videos soon!

[@ilanaizelman3993]

@@LucidProgramming Done! :) Are you during Mock Interviews? Or know someone who does?

[@LucidProgramming]

@@ilanaizelman3993 Thank you, Ilan! Your support is very much appreciated! And yes, I do perform mock interviews, coaching, and consulting services for software-based job preparation. If you're interested in setting something up, you're free to reach out to me in the "About" section of my channel and we can coordinate from there if you like. Cheers, and best of luck in your preparation in any case!

[@hussainaqeel7371]

Great Stuff! Made it very easy to understand! Thanks!

[@LucidProgramming]

Cheers! If you enjoyed and benefited from my content, please consider liking the video and subscribing to the channel for more content like this. If you would like to support the content creation on this channel please consider unblocking ads when watching my videos as this is how I support my time to make content. I hope to be putting out more similar videos soon!

[@hussainaqeel7371]

@@LucidProgramming sure!

[@LucidProgramming]

@@hussainaqeel7371 Cheers, thank you!

[@faithnwokoma]

def postorder_print(self, start, traversal): #Left -> Right -> Root if start: traversal = self.postorder_print(start.left, traversal) traversal = self.postorder_print(start.right, traversal) traversal += (str(start.value) + "-") return traversal

[@LucidProgramming]

Cool, thanks for sharing!

[@hemesh5663]

Dude you earned a subscriber and a fan

[@LucidProgramming]

Thank you, man! Sincerely appreciate the support and love! Cheers!

[@DanielGarcia-uq8yz]

I'm only 3 min in but love the explanations. Thanks!

[@LucidProgramming]

Great to hear, and thank you for the kind words!

[@Rich65501]

Beautiful presentation.

[@LucidProgramming]

Thank you! If you like my content, I've been working on some projects during the past couple of months. If you would like to stay up-to-date, please consider subscribing to my mail list. Also, if you haven't already, please consider subscribing! I really appreciate the support, and if you want to support the channel, I do have a PayPal link (www.paypal.me/VincentRusso1) for donations that go directly to the creation of content on this channel. I hope that the content I provide there will enhance the videos on my KZbin page. bit.ly/lp_email

[@musclecode3771]

Amazing explanation well worth the time to watch.

[@LucidProgramming]

Cheers! If you enjoyed and benefited from my content, please consider liking the video and subscribing to the channel for more content like this. I hope to be putting out more similar videos soon!

[@vishnukumavat7489]

Thanks for such a cool implementation explanation.

[@LucidProgramming]

Cheers! If you enjoyed and benefited from my content, please consider liking the video and subscribing to the channel for more content like this. I hope to be putting out more similar videos soon!

[@SaltAndVi]

phenomenal video, thank you so much!!!

[@LucidProgramming]

Cheers! If you enjoyed and benefited from my content, please consider liking the video and subscribing to the channel for more content like this. If you would like to support the content creation on this channel please consider unblocking ads when watching my videos as this is how I support my time to make content. I hope to be putting out more similar videos soon!

[@hoangphuoccao117]

Great explanations! Thank you very much!!

[@LucidProgramming]

Cheers! If you enjoyed and benefited from my content, please consider liking the video and subscribing to the channel for more content like this. If you would like to support the content creation on this channel please consider unblocking ads when watching my videos as this is how I support my time to make content. I hope to be putting out more similar videos soon!

[@robn8656]

Just incase there's someone like me out there: I struggled forever to understand how this code and recursive data structures generally worked until I finally understood recursion. Al Sweigart has a great video on recursion but essentially recursive functions use a stack method to determine how the functions are called. the subsequent functions can't be called until the previous one has been removed from the stack. each number being appended to the string is that function being removed from the stack. So, counterintuitively, the string begins with one because it's the LAST METHOD to be cleared from the stack. All, the other methods cycle through the tree first, appending their value to the string. It sounds backwards, I know. I don't even know if I explained it well but you have to understand recursion to understand BST. Watch Sweigart's video.

[@LucidProgramming]

Cool, thanks for sharing and thanks for watching!

[@olivierbegassat851]

Very valuable explanation! Thanks : )

[@LucidProgramming]

Glad to hear it, and thanks for watching! :)

[@olivierbegassat851]

​@@LucidProgramming The preorder_print function is the sort of thing I would have had a hard time coming up with myself. My naïve attempt would have been to have some list or dictionary of nodes whose left child you've already visited ... instead you simply wrote (amongst other things I'm skipping) traversal = self.preorder_print(start.left, traversal) traversal = self.preorder_print(start.right, traversal) This is really interesting, it's orders of magnitude more elegant and succinct. I wouldn't have come up with it. I would have written some longwinded solution using an extra list or dictionary. Do you know a book or online resource that contains Python implementations of many standard data structures ?

[@LucidProgramming]

@@olivierbegassat851 Thanks for the comment. Honestly, you can probably just Google for Python data structures and find something reasonably good.

[@HanisaMHilole]

Thank you! Explained it very well.

[@LucidProgramming]

Cheers! If you enjoyed and benefited from my content, please consider liking the video and subscribing to the channel for more content like this. If you would like to support the content creation on this channel please consider unblocking ads when watching my videos as this is how I support my time to make content. I hope to be putting out more similar videos soon!

[@kl-je3up]

explains it way better than my ds&a textbook lol

[@LucidProgramming]

Cheers! If you enjoyed and benefited from my content, please consider liking the video and subscribing to the channel for more content like this. If you would like to support the content creation on this channel please consider unblocking ads when watching my videos as this is how I support my time to make content. I hope to be putting out more similar videos soon!

[@toderickson6106]

good clarification skills, gave it a like

[@LucidProgramming]

Very much appreciated--thank you for the support!

[@felipepardosuarez2364]

Great video. Thank you!

[@LucidProgramming]

Thank you! If you like my content, I've been working on some projects during the past couple of months. If you would like to stay up-to-date, please consider subscribing to my mail list. Also, if you haven't already, please consider subscribing! I really appreciate the support. I hope that the content I provide there will enhance the videos on my KZbin page. bit.ly/lp_email

[@theguildedcage]

Awesome tutorial! Thanks.

[@LucidProgramming]

Thank you, Philip! I'm glad you found the tutorial useful! Cheers, and thanks again for watching.

[@DavidKaplanProgramming]

Really good tutorial man! Thanks

[@LucidProgramming]

Thank you, David, I'm very happy to hear that you enjoyed the tutorial! Cheers.

[@zarioiubogdan1164]

Hi there! Thank you so much for this! I just discovered your videos and they are so helpful! I was struggling a lot to understand how I could implement and traverse a binary tree. There are countless videos about this but yours really made me understand and gave me hope that with time and practice I could learn these concepts. I saw you have videos on many data structures and I plan to go through all of them and try to understand. Could you please also cover graph implementation and traversal in Python? Thank you again for your help! Wish you the best!

[@LucidProgramming]

You can feel free to make suggestions on my Patreon page. This would streamline what you want to see and also help to support my channel. www.patreon.com/lucidprogramming

[@cryptoTeacherAcademey]

Thank you so much for the great tutorial!!

[@LucidProgramming]

Thank you! If you like my content, I've been working on some projects during the past couple of months. If you would like to stay up-to-date, please consider subscribing to my mail list. Also, if you haven't already, please consider subscribing! I really appreciate the support. I hope that the content I provide there will enhance the videos on my KZbin page. bit.ly/lp_email

[@ramiz3570]

Amazing explanation, thanks!

[@LucidProgramming]

Thank you! If you like my content, I've been working on some projects during the past couple of months. If you would like to stay up-to-date, please consider subscribing to my mail list. Also, if you haven't already, please consider subscribing! I really appreciate the support, and if you want to support the channel, I do have a PayPal link (www.paypal.me/VincentRusso1) for donations that go directly to the creation of content on this channel. I hope that the content I provide there will enhance the videos on my KZbin page. bit.ly/lp_email

[@rohith8269]

great explanation!!

[@LucidProgramming]

Cheers! If you enjoyed and benefited from my content, please consider liking the video and subscribing to the channel for more content like this. If you would like to support the content creation on this channel please consider unblocking ads when watching my videos as this is how I support my time to make content. I hope to be putting out more similar videos soon!

[@vnpikachu4627]

Great work very easy to understand i really appreciate what you are doing to help us

[@LucidProgramming]

Hey Huru. Thank you very much for that comment. It's really great to hear that these videos have been helpful to you. I really get a lot of enjoyment from doing so as well, so the benefit is mutual! Cheers and thanks again for watching.

[@vnpikachu4627]

Just 30 minutes i go from nothing to understand a lot more about tree could you please make a tutorial about graph and some algorithm about tree ?

[@LucidProgramming]

Really happy to hear that. Yes, graphs are most certainly coming up soon! Thanks for the suggestion and for the comment!

[@gunabalang7034]

crystal clear

[@LucidProgramming]

Cheers! If you enjoyed and benefited from my content, please consider liking the video and subscribing to the channel for more content like this. If you would like to support the content creation on this channel please consider unblocking ads when watching my videos as this is how I support my time to make content. I hope to be putting out more similar videos soon!

[@jayaramakapil5295]

All Superheroes don't Wear Capes. Some wear Suit too :)

[@LucidProgramming]

Haha, well I hope the videos are helpful to you. Cheers, and thanks for watching!

[@gargoth]

great video! i would suggest matching the colors of the slides to the colors of the editor, because the sudden switch from dark to light doesn't sit well while watching. thanks!

[@LucidProgramming]

Thanks for the feedback, that's very helpful to know! Thanks again for watching as well!

[@gargoth]

no problem dude, i really appreciate your videos!

[@LucidProgramming]

@@gargoth Cheers, thank you!

[@Mankind5490]

This is fantastic, thank you

[@LucidProgramming]

Cheers! If you enjoyed and benefited from my content, please consider liking the video and subscribing to the channel for more content like this. If you would like to support the content creation on this channel please consider unblocking ads when watching my videos as this is how I support my time to make content. I hope to be putting out more similar videos soon!

[@Mankind5490]

@@LucidProgramming Already done!

[@drcylon]

I think there is a little error in the "print_tree()" function, it shouldn't be "tree.root" it should be "self.root" ! Plus the "postorder" error pointed out in some comments below! Still, it is a great effort. Thanks.

[@LucidProgramming]

Indeed, thank you for the comment!

[@nx8221]

Dude thank you for this!

[@LucidProgramming]

Thank you! If you like my content, I've been working on some projects during the past couple of months. If you would like to stay up-to-date, please consider subscribing to my mail list. Also, if you haven't already, please consider subscribing! I really appreciate the support, and if you want to support the channel, I do have a PayPal link (www.paypal.me/VincentRusso1) for donations that go directly to the creation of content on this channel. I hope that the content I provide there will enhance the videos on my KZbin page. bit.ly/lp_email

[@supamdeepbains5172]

best explanation on youtube!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

[@LucidProgramming]

Haha, cheers Spamdeep, I really appreciate that :). Happy coding, and thanks for the kind comment!

[@ravitanwar9537]

@@LucidProgramming actually the name is supamdeep not spamdeep

[@LucidProgramming]

@@ravitanwar9537 Whoops. Must have been my autocorrect? Sorry about that. Thanks for catching, Ravi.

[@ajayprajapati2453]

Hi..Thank you so much for uploading video with nice explanation..

[@LucidProgramming]

Cheers! If you found the video helpful, I would definitely appreciate any a like/subscribe/share! Thanks for watching!

[@valentynsson5969]

Legend perfect explanation thank´s I like it.

[@LucidProgramming]

Thank you! If you like my content, I've been working on some projects during the past couple of months. If you would like to stay up-to-date, please consider subscribing to my mail list. Also, if you haven't already, please consider subscribing! I really appreciate the support, and if you want to support the channel, I do have a PayPal link paypal.me/VincentRusso1 for donations that go directly to the creation of content on this channel. I hope that the content I provide there will enhance the videos on my KZbin page. bit.ly/lp_email

[@neildutoit5177]

checking for None using a bool cast is also an anti-pattern. Use "if start is not None" instead.

[@ГоранДеспотовић]

Thank you sir!

[@LucidProgramming]

You're very welcome. Thank you for watching!

[@ГоранДеспотовић]

@@LucidProgramming I watched many videos on this subject, yours is spot on! You're a great teacher, thanks again!

[@LucidProgramming]

@@ГоранДеспотовић thank you for the kind words!

[@raakobihai2967]

Thank you soo much for this!

[@LucidProgramming]

Cheers! If you enjoyed and benefited from my content, please consider liking the video and subscribing to the channel for more content like this. If you would like to support the content creation on this channel please consider unblocking ads when watching my videos as this is how I support my time to make content. I hope to be putting out more similar videos soon!

[@kowyo]

Thank you for this video

[@Me-ex7qg]

wish i found your channel earlier. very good

[@LucidProgramming]

Thanks, TJ. I'm happy you stumbled on it now, and I hope the videos serve you well! Thanks for the comment, and happy coding!

[@zewdiherring9528]

Thanks! Helpful :D

[@LucidProgramming]

Thank you for watching, and glad to hear that it was helpful!

[@cdemr]

I am on Pycharm and I am a beginner. I do not understand what you're doing at 18:15. I can force-erase the consol but I can't write inside it.

[@alexradu1921]

I've implemented the traversion with a list version, to be more useful... and also I've modified the print function not to return the list, and just directly print it (because, it's called "print_tree")... class BinaryTree: def __init__(self, root): self.root = Node(root) def print_tree(self, traversal_type): if traversal_type == "preorder": print(self.preorder_list(self.root, [])) elif traversal_type == "inorder": print(self.inorder_list(self.root, [])) elif traversal_type == "postorder": print(self.postorder_list(self.root, [])) def preorder_list(self, start, traversal): ''' Root->Left->Right ''' # start = node update on every recursive call # traversal = list with values of tree in preorder if start: traversal.append(start.value) traversal = self.preorder_list(start.left, traversal) traversal = self.preorder_list(start.right, traversal) return traversal def inorder_list(self, start, traversal): ''' Left->Root->Right ''' if start: traversal = self.inorder_list(start.left, traversal) traversal.append(start.value) traversal = self.inorder_list(start.right, traversal) return traversal def postorder_list(self, start, traversal): ''' Left->Right->Root ''' if start: traversal = self.postorder_list(start.left, traversal) traversal = self.postorder_list(start.right, traversal) traversal.append(start.value) return traversal tree = BinaryTree(1) tree.root.left = Node(2) tree.root.right = Node(3) tree.root.left.left = Node(4) tree.root.left.right = Node(5) tree.root.right.left = Node(6) tree.root.right.right = Node(7) print(tree.preorder_list(tree.root, [])) #you can print the llist directly tree.print_tree("preorder") tree.print_tree("inorder") tree.print_tree("postorder")

[@alexradu1921]

ALSO *Thank you* for this very well explained video on trees using python... If i search the Internet for a Binary Tree in Python I found just very complicated unnecesary syntax.

[@LucidProgramming]

Cool, thanks for sharing!

[@vitaliano01]

Thank you.

[@LucidProgramming]

Cheers! If you enjoyed and benefited from my content, please consider liking the video and subscribing to the channel for more content like this. If you would like to support the content creation on this channel please consider unblocking ads when watching my videos as this is how I support my time to make content. I hope to be putting out more similar videos soon!

[@test-y1p7r]

If I'm not mistaken, depth of root node is 0. Root node is at level 0, not 1 :)

[@ishannoying]

loved it!

[@LucidProgramming]

Thank you! If you like my content, I've been working on some projects during the past couple of months. If you would like to stay up-to-date, please consider subscribing to my mail list. Also, if you haven't already, please consider subscribing! I really appreciate the support, and if you want to support the channel, I do have a PayPal link (www.paypal.me/VincentRusso1) for donations that go directly to the creation of content on this channel. I hope that the content I provide there will enhance the videos on my KZbin page. bit.ly/lp_email

[@rohitashpathak260]

I started learning python data structure only after watching your videos. Thank you so much. Do you have some projects in python that can we can go through, it will help to build the overall confidence level in coding.

[@LucidProgramming]

Great to hear. As for projects, I offer tutoring. You can reach out to my email and I can provide you rates and ideas. Cheers!

[@rohitashpathak260]

LucidProgramming Thanks for your response but if you have some free contents that you can share will be a great help.

[@LucidProgramming]

@@rohitashpathak260 Due to time constraints, I may have to back away. I can suggest the other content on my KZbin channel, though!

[@Iamnoone56]

Please make videos on graph and please add more questions on trees 😭😭

[@LucidProgramming]

You can feel free to make suggestions on my Patreon page. This would streamline what you want to see and also help to support my channel. www.patreon.com/lucidprogramming

[@gokusaiyan1128]

What are your vim settings/plugins? I like it

[@LucidProgramming]

Good question! Much of my configuration is covered here: kzbin.info/www/bejne/rJ3FZKSLnrhlkLs

[@sarvarjuraev1376]

Thank you very much

[@cudanakiju0]

@17:04 you type tree.root, shouldn't that be self.root instead?

[@bronik7]

That's what I thought. It's not clear to me how object will know it's instance

[@samkruse6242]

This is gold

[@LucidProgramming]

Thanks, Sam! I'm glad that this video was useful to you. Thanks for the comment and for watching! Cheers.

[@user-vj3fs4cq9n]

amazing video

[@hackytech7494]

Thank you so much for your explanation it was wonderful. I am having one doubt we haven't coded to go up if we don't have left or right children, then how it goes up programaticaly

[@LucidProgramming]

Hi Tammay. Thanks for the comment. You might want to check out my recursion playlist if that part is tripping you up. I think it clarifies your confusion. Cheers!

[@hackytech7494]

@@LucidProgramming Ok Thank you so much sir. I will go through that playlist first.

[@LucidProgramming]

@@hackytech7494 Cheers!

[@ninjaturtle205]

in postorder definiition you recursively called inorder. (i think you forgot to update after copy pasting) The answerjjjjj should be 4-5-2-6-7-3-1- excellent video. i understood everything

[@LucidProgramming]

Thank you! And indeed, I pinned a comment that explains this discrepancy. Good catch in any case!

[@jingfenghong2312]

These are awesome videos I have ever seen. I have a question, why don't you use self.root in print_tree() function, but use tree.root?

[@LucidProgramming]

Thanks! And either convention is fine there. Using self.root would work just as well. Cheers!

[@jingfenghong2312]

@@LucidProgramming Thank you a lot, these videos would definitely help me in my future career interview! I will recommend it to other friends.

[@LucidProgramming]

@@jingfenghong2312 Thank you, I sincerely appreciate that!

[@vagadellestelle]

Excellent explanation, thank you. However, I don't understand why you need a preliminar class "Node"? It wouldn't be sufficient to code the class BinaryTree as simply like: class BinaryTree def __init__(self, root): self.root = root self.left = None self.right = None ?

[@LucidProgramming]

You could, although it does make sense to split things up as they are fundamentally different objects. It just makes things a bit clearer to understand.

[@vagadellestelle]

@@LucidProgramming thanks a lot. Will follow your channel for your excellent explanations!

[@LucidProgramming]

@@vagadellestelle Thank you, I appreciate the support!

[@РоманРахлин]

Thank you 🙏🙏🙏

[@shivamdubey9225]

Please make videos on bfs and dfs and some of its important use , in python it is hard to find on utube

[@LucidProgramming]

It's on my list of videos to make! Subscribe and stay tuned!

[@debashishchakraborty7924]

@@LucidProgramming ..you are not making new videos, no one can explain python data structures better than you. please do something....

[@LucidProgramming]

@@debashishchakraborty7924 Lots of balls up in the air at the moment. Right now, I'm putting together a book that I hope to have video content for. Stay tuned!

[@vnaveenkumar982]

@@LucidProgramming Thanks for the tutorial... please make such videos in python about data structures and you explain it like a pro please continue..

[@LucidProgramming]

@@vnaveenkumar982 Thank you! If you like my content, I've been working on some projects during the past couple of months. If you would like to stay up-to-date, please consider subscribing to my mail list. Also, if you haven't already, please consider subscribing! I really appreciate the support, and if you want to support the channel, I do have a PayPal link paypal.me/VincentRusso1 for donations that go directly to the creation of content on this channel. I hope that the content I provide there will enhance the videos on my KZbin page. bit.ly/lp_email

[@bronik7]

(17:57) Why in preorder_print (line 4) you passing tree.root? why not self.root? to me it's not clear how Class knows about it's instance? Can you please explain? Thank you

[@someshsangwan3768]

Thnq sir I am facing a TypeError: Binary tree takes no argument . Tell me about this

[@LucidProgramming]

You might want to check your code against my GitHub code.

[@khavishbhundoo3792]

Could you include the link for the presentation as well.It serves as a quick recap.Thanks for the great explanation.

[@LucidProgramming]

At the moment, those slides are a bit all over the place. However, it would certainly not be an issue to clean them up and post a link in the description of this video. Might take me a while to get around to it, but I'll add it to the list. Thanks for the suggestion and thanks for watching! :)

[@nivi8319]

@19:30 i don't know if my doubt sounds silly but I want to know how it is moved upward when there is no left or right subtree I didn't get that please can you explain?? and thank you for this amazing video : )

[@LucidProgramming]

Thanks, Nivi. I think you might benefit from checking out my recursion playlist as that might clear this up. Hope that helps!

[@nivi8319]

@@LucidProgramming ohh thanks a lot , I'll check that

[@LucidProgramming]

@@nivi8319 Cheers, let me know if you have questions!

[@alessiopellegrini523]

Shouldn't it be self.preorder_print(self.root, " ") in the helper function of the BinaryTree? There is no tree variable in the class and the only way the code is still running correctly is because "tree" happens to be defined outside of class, no?

[@rhythmsaparia8788]

I have a doubt, after a while adding nodes by writing tree.root.left.right.left bla bla becomes a cumbersome process, if you could suggest a better and easier way to add nodes than it would be a great help, thanks.

[@software-sage]

There must always be a way!

[@armans4306]

thanks good tutorial; tho you have a bug which is python's fault to be honest. It has allowed you to do this: return self.preorder_print(tree.root, "") ; it had to be self.root

[@pythondev2631]

It is the first time that I come across Instantiate an object of another class without passing it as an argument (Node in BianryTree). Is this a common practise?

[@VarunKumar-pz5si]

Can you explain the recursion in pre-order traversal?

[@LucidProgramming]

Got a whole playlist on recursion you can check out!

[@mohamedhabas7391]

when i saw vim, i trusted you :)

[@LucidProgramming]

Haha, cheers!

[@prakhargurha1427]

Why is it necessary to define class Node(object) and not class Node() simply as we did in linked list.What's the significance of object

[@LucidProgramming]

They are equivalent. The former is how things were done in Python 2.7, and the latter is more modern.

[@musictrader8990]

What is the "object" argument you pass when creating class?

[@LucidProgramming]

It's legacy Python. You can do either class Name: or class Name(object):

[@MomoDiff48]

Just a small question, is it necessary to make whole class BinaryTree just for the root node? or it has something to do with python versions?

[@michaelscarn7375]

I don't get why the program doesn't stop and return "traversal" string in preorder as soon as it reaches left most node ( 4 in your example). There is no left or right child node at 4. What makes it to go up back to 2.

[@LucidProgramming]

I think the confusion here might be arising from understanding how recursion is being used. If that is the case, I do have a playlist on recursion that might clear some of this confusion up. Thanks again for watching!

[@michaelscarn7375]

@@LucidProgramming I got it now, thanks to Your other video on tree traversal, where you went through entire funtion run. Glad I found Your channel. You along with Corey Schafer among my top youtube coding tutors. Wish you All the Best.

[@LucidProgramming]

@@michaelscarn7375 Corey Schafer is great. Very flattering of you to put us in the same camp. Cheers, and thanks again for watching!

[@MsKshitij1234]

@@michaelscarn7375 which video is it, I am still stuck with this probelm not able to understand the flow

[@NoorAli-uh4uq]

Amazing content but one question, why I thought in Binary trees the left_child should be less than the root, in that case if the root is 1 then the left_child cannot be 2. May be I am wrong but I appreciate if clarify that, thanks again for the amazing content.

[@LucidProgramming]

Thanks Noor. Regarding your comment, you're thinking of binary search trees. I have a whole playlist on them as well that you might enjoy. Cheers!

[@NoorAli-uh4uq]

Thanks for reply, I am checking your page but cannot see the Binary Search Tree vidoes, I have seen Data structures which consists of 40 video and the last 7 deals with Trees, I am not sure if they are contained there. Thanks.

[@LucidProgramming]

Hi Noor. There is a BST playlist. You can find it here: bit.ly/lp_bst. Cheers!

[@NoorAli-uh4uq]

Thanks @@LucidProgramming

[@LucidProgramming]

@@NoorAli-uh4uq No problem! If you like my content, I've been working on some projects during the past couple of months. If you would like to stay up-to-date, please consider subscribing to my mail list. Also, if you haven't already, please consider subscribing! I really appreciate the support. I hope that the content I provide there will enhance the videos on my KZbin page. bit.ly/lp_email

[@kshitijtewari2025]

Thanks Sir, what is difference b/w class Node(object): and class Node:

[@LucidProgramming]

No difference at all!

[@amithpandit4043]

That's right. No difference. According to the link below: in Python 2.7 and older, you need to add the object inside parenthesis. In Python 3 and above, it doesn't make a difference. introtopython.org/classes.html

[@abhinavreddy5350]

@@amithpandit4043 kk tq :)

[@asiacaster3663]

Im trying to wrap my head around saving the recursive calls in two variables both named traversal in the preorder_print function.. I have spent quite a lot of time learning recursive functions recently (including your videos and others), and thought I understoodd them well for things like binary search and what not, but I still can not picture/map what is going on in my head with those calls in that function, I am getting extremely frustrated right now. Great channel btw, subscribed.

[@LucidProgramming]

Recursion is one of those things that I think takes a while in wrapping ones head around. I've worked directly with Sam from Byte-by-Byte and he has some really fantastic material on recursion. Specifically, he provides a free e-book on recursion and dynamic programming that has really great visuals of which I haven't really seen elsewhere. I'd recommend giving that a look. And, also, don't get discouraged. Learning these things takes time and practice. Thanks for the support and subscription.

[@MrAgj200]

you say to look at your series of linked lists videos, but then dont link them. and if you do find the linked lists playlist, the first video in the series says its a continuation, so which is the first video, but who know what that is????

[@robinmujician]

"A Binary Search tree is a binary tree in which nodes which have lesser value are stored on the left while the nodes with higher value are stored at the right." (From GeeksforGeeks). You seem to have a different definition. Which one is considered "standard" please?

[@LucidProgramming]

You are confusing binary trees with binary search trees. A binary search tree is a subset or type of binary tree that has the ordering property you are referring to. Binary trees do not have this ordering imposed on them. Note that I have a playlist on binary trees and also binary search trees, as they are distinct entities. Hope that clears things up for you.

[@Mcbridefam20129]

Hi, thank you so much for the video. I am a little confused still about one thing. When in the preorder traversal, when it comes to a leaf that dosn't have a left or right node, in the code how does it go backwards to the previous node or back to the root?

[@LucidProgramming]

I would encourage you to check out my playlist on recursion, as it seems you have a gap in understanding how recursive calls are treated.

[@conquerworld_in]

Hello sir, I am not able to understand that how everything is happening here as in if how are we writing start.value with inheritance and those things!

[@LucidProgramming]

You might want to look into Python classes to clarify this.

[@conquerworld_in]

@@LucidProgramming I saw that but then also I wasn't able to understand

[@LucidProgramming]

@@conquerworld_in You might need to be more specific. I offer tutoring services if you feel like you're stuck on a subject.