Python Generators Explained

[@goboy6882]

I started programming 60 years ago. Thank you Tim for teaching an old dog new tricks.

[@Ian-bb7vv]

wow, life long learning!!!

[@piadas804]

Wow

[@JasonJorgensonPhD]

What was it you were learning 60 years ago? Was it COBOL? Fortran? I started programming in 1980/81 but it was BASIC by then, and I graduated to COBOL and Fortran, eventually settled on C++ as my go-to language.

[@ketso-l7b]

Lies!🥱🥱🥱

[@thelavagod]

​@@ketso-l7b how u know😂

[@williamselinder9138]

I very rarely leave comments on tutorials, but this was so incredibly well and robustly explained that I seriously need to leave my comment of appreciation, it was so clear to understand!

[@vinni113]

i watched this video just to learn something new about python, turns out the generator is really applicable in my code and has helped memory usage heaps. Thanks!

[@gustavocinci4044]

Thanks Tim. You have become the go-to guy when I learn stuff and get stuck. your explanations are very practical. as a new programmer who's attempting to beef up my resume, I have been teaching myself python. you have been a great resource, keep it up. THANK YOU!

[@saishyam8583]

I would love to see a video on how you record and edit your videos Man This is some real good quality content!!

[@tyrelllaszlo6024]

Great video and explanation! Was going to look for “how to process large amounts of data”, but clicked on this instead. Turned out to be the core of the answer👍

[@Factory400]

It is nice and refreshing to see a presentation of the back-end logic to the magic functions we have in Python. As much as I love the built-in functions - I really love knowing how they do what they do.

[@ChandanSingh-bh7wu]

******BEST GENERATOR EXPLAINATION********** read 3 books + 4 online tutorials, still confused about Generators******* Finally, got it ............!!!! Awesome Brother !!!!!

[@harshraj22_]

could have added example of "yield from" as well. A great coding exercise would be, print inorder traversal of binary tree using generators.

[@TechWithTim]

Great idea!

[@xx-jk1iq]

ok please explain what "inorder traversal of binary tree" is

[@gregfrost8399]

@@xx-jk1iq Traversing a tree is just the order in which you access it's nodes. In-order traversal of a binary tree means you visit the left branch, then the current node, and then the right branch. Basically put it visits the nodes in ascending order.

[@xx-jk1iq]

@@gregfrost8399 but from what I thought, a binary tree isn't a linear sequence. So how would that work

[@gregfrost8399]

@@xx-jk1iq Say we have the following tree: A / \ B C / \ D E In order traversal does the following: 1. searches the left branch until it finds a leaf node 2. visits (e.g. prints) the current node 3. searches the right branch until it finds a leaf node Once it has completed the 3 steps it will return upwards to it's parent node The result = (D, B, E, A, C)

[@NabeelButt]

Good thing about this video is that it walks you through other concepts too such as class and dunder methods which is kind of a good refresher to what I have studied earlier. You've earned a subscriber Tim!

[@bipolarchemist]

For a deeper dive into generators, you can go into how you can use .send to update process parameters that may not have been relevant when initially creating the object. This was an area that originally stumped me when I was looking at some more advanced examples of generators as the function took in one set of parameters, but the subsequent calls with yield accepted different parameters. A very neat trick and one of the reasons why I find myself growing more enamored with the language.

[@lepidoptera9337]

One can update objects at any time with a call to an object method just like one can update the value in a loop variable with a simple assignment. Writing a loop and an assignment makes the code readable for absolutely everybody with even the slightest amount of knowledge about procedural programming languages. Using send() will make 99% of programmers scratch their heads (including the ones who know what it does) and ask what kind of idiot will use such a construct. Guess who they mean by "idiot". They mean you. And that, by the way, includes yourself. You will call yourself an idiot for using this construct the first time you have to read your own code six months later. Simple is beautiful. Keep it simple.

[@MissingTricks]

This video provides a clear image of how it works. Thank you.

[@ChromaDotNova]

I appreciate the video, Tim! I have a much better understanding of Python generators now.

[@fredericoamigo]

Great video! Best explanation I’ve seen so far on this topic!

[@roarba]

This channel is just so incredible! i can't tell how much i learned from this channel, thank you

[@michapodlaszuk9025]

good stuff Tim, there's never enough of knowledge about python

[@YEM_]

Best explanation I've heard yet.

[@Adedeji-v9z]

At 5:29, the range() function is actually an iterable because it doesn't have a _next_ method, only an __iter__method, iterators by default have both the __iter__ and __next__ method, while using for loop, the for loop applies the __iter__ method on range() creating an iterator (specifically a range iterator object), then calls the __next__ method on the iterator object, I guess the range() function just happens to be that iterable which implements memory management efficiently than other iterables like list, tuples, strings.

[@parvishrao6414]

Tons thanks, only video which clearly said what is iterator and generator - CRYSTAL CLEAR.

[@LNMLucasMasiero]

Thanks you. This was really interesting. It's crazy how the most someone knows about how something works, then for intuition you can understand other stuff or libraries created from others. One of the usefully methods I use as a fast document of a library is "dir"

[@TheRealKitWalker]

Wow! This was so refreshing and highly insightful. Thanks so much Tim for this really helpful video on generators. It helped me a lot understand this better!

[@STFU665]

Really appreciate your videos. Thank's for sharing your knowledge. I'm just at the start with Python deep-diving, but already it keeps getting me staying awake at night. So many possibilities :D Keep on the good work

[@rodrigo2112-]

You're a great teacher, congrats!

[@CaratacusAD]

This was an awesome video Tim. I'm learning about Deep Learning and generators have been particularly useful for chunking up huge datasets for feature extraction as it would be impossible to read them all into memory on my laptop. Now I understand how and why this works as a Python newbie. The explanation on Iterators was great too. I love the nuts-and-bolts detail on what’s going on under the hood. Many thanks.

[@omarelsebaey9589]

the example for the generator is perfect , thanks!!!

[@anirbanc88]

i love your videos man, and your clarity of explanations, carry on!

[@network_noob]

Now i can finally understand generators! Thanks Tim!!

[@stele339]

Хвала!

[@abdullahmohammed6115]

Love your vids! Great as always!

[@ddbarenco]

Amazing explanation! Learn a lot from it. Thank you soo much!!

[@davidringhage]

Amazing video Tim. Thank you

[@gustavojuantorena]

This video has so much value! Thank you

[@onlyforscience8255]

I learned new things which don't know anything about that. Thanks to make such a nice video for us. ☺️☺️👏👏

[@Mdroudian]

Great video. You have a good format. Don't change it =)

[@NearLWatson]

Great job breaking it down 👍🏼

[@estebangarro7254]

Excellent Video, thanks!

[@danielmarx3106]

You can use ctrl + d to copy a line to the next line without copy pasting in pycharm, not sure if something like that in sublime.

[@manishsingh900]

It really is a great video. Thank you!!!!. One of the best generators video generated🙂.

[@enzovalendino606]

Hi Tim, you keep providing us useful contents: I'm glad for everything you've been doing! I'm truly interested in CS, and curious about how much of these information you have learned at university or on your own. Could you please answer me?

[@vammy55]

Great stuff mate,thank you and cheers!

[@amalkrishnas1696]

Thanks for the video, well explained

[@bahdcoder]

You are the best out there man

[@korkunctheterrible4302]

09:46 and on: Hi I'm a total noob and I don't get why for loop is able to pick the iteration up from where the last next call left it. why does the for loop know what happens before it? Is where next stops also stored and the loop preprogrammed to check that address? I'm sorry if I've misused words, I just don't know how else to ask about it. Any tip would be much appreciated. Also thanks to the maker of this video.

[@eddywang5035]

Useful tutorial for me. Thanks.

[@Barejs]

awesome content, keep up with these videos Tim

[@antmitchell9930]

You should put the 'Pause 1' before the 'yield 1', I suspect, otherwise the pause text appears on the next call, not the one it refers to. Just learning Python - this is great.

[@whatdoiputhere5089]

yeah, he should've done that so everyone can know when is the 'Pause 1' getting printed

[@user-zb8tq5pr4x]

but the execution pauses after the yield, so pause 1 before makes no sense.

[@bradyb2415]

First time i understood what you are saying....☺

[@johnnytoobad7785]

Looking forward to "Learning Cobol with Tim" course !

[@innocentharelimana4449]

we, we had teachers who didn't know these stuff😂😂😂, and graduated without this knowledge😊😊😊

[@barbaraulitsky8292]

This is a super tutorial! Super helpful and clear explanation! Tim, you are awesome! Thank you so much!!!

[@aryankathawale9269]

lets goo new tech with tim

[@lam-thai-nguyen]

thank you, Tim

[@Kema109]

@14:40, if I would print(next(iter(x))) it would give me 1 thats true, but if I would do that again, I would get another 1 and so on. So it does not go to the next Element. That was kind of confusing to me. So I guess, you have to make the variable "x" an iter first, and then you can use the next(x) function to "jump" to the next element. Or did I not understand that right?

[@haneulkim4902]

Thanks Tim. One question. So creating generator don't even take up disk space? Say I have a for-loop that downloads a file, yield data, then delete the file where end result is a generator. This won't take up disk space and only memory upon calling __next__()?

[@alexandruteodor3585]

Thank you!

[@boooringlearning]

thats brilliant video!

[@JaBoss397]

Thank you !!

[@yoyokoko5153]

Thanks for the good stuff

[@UgochukwuEzeani-ut6vd]

Awesome 🎉

[@alexramirez5104]

Damn I love this channel

[@mgmartin51]

when i put the code at 7:29 into IDLE, (for i in y: print(i)), nothing happened. You got the list output. Why is that?

[@nicholas_obert]

Could you make a video on C extensions for Python? It took a while for me to learn as there aren't many resoruces out there and the documentation is partially outdated, but the speed increase using such extensions is exponential with regards to input size. I think a tutorial on this topic would prove highly useful to newcomers. I've already written an article about them on Medium, but I think you, Tim, can do a much better job at explaining them.

[@hossumquat]

Yes, this would be nice. Does Tim know C though? If so, I've love to learn how to integrate C and Python

[@nicholas_obert]

@@hossumquat he has made a series about C++, plus C is very easy at a beginner level.

[@hossumquat]

@@nicholas_obert Ah, ok, didn't know that. I'd guess he already knows this then and could teach it. Awesome!

[@servantofourlordjesuschris6456]

Thanks!

[@jphvnet]

If for loop stops by the exception, it's not clear where gen() raise the exception. Or there is a different logic inside for() .

[@robinferizi9073]

I like how the first generator example is literally obscolete because you used for i in range: to say for i in range:

[@GoziePO]

thank you!!!

[@elitearmedforce]

Wow, really well explained, good that stumbled upon this. If u can do the same with other python(decorators...) and c++ concepts like this, pls. Subbed and liked,

[@ScOrPiOnE905]

I'd like to make a note regarding the execution of generators, maybe somehow it'll be useful to someone. A generator will not re-iterate if it has already finished the range it was given in a variable for example. However, it will re-iterate if you call directly to the generator itself, not the variable you might have assigned it to. You can try this out with a range, a for loop and the print function (I've posted some code below to give an example) Code to try it out for yourselves below (I hope the formatting won't be broken): def generator_example(n: int): print(" Generator has started. ") start = 0 while start < n: print("Generator is returning {}".format(start)) yield start start += 1 range_example = generator_example(5) list_example = [] print(next(range_example)) # Exhausts 1 of the total of 5 values in the range_example variable. input("Press Enter to proceed.") for values in range_example: input() list_example.append(values) # Only 4 values remain to be appended. print() print("Generator has already finished and will not execute the for loop in the code in the same variable (range_example) below.") print("The print(next(range_example)) function will also exhaust one execution of the generator.") for i in range_example: list_example.append(i) print() print("Calling the function itself, however, will execute the for loop however many times you want.") print() for j in generator_example(5): list_example.append(j) for k in generator_example(5): # print(k) list_example.append(k)

[@korkunctheterrible4302]

So where is the information for the first next() yield stored, in range_example ? and if it is stored, why does that not take up memory or is it that it just takes smaller memory in comparison? when you call the generator_example function with the argument 5, does the function def block create 5 spots to fill for in the range_example first, and one gets filled by the first "next", and a mark is put in there? does the info for where the mark will go get overwritten in the same space of memory with each execution? lol sorry for my dreadful misuse of any term or anything and I hope you still understand my question (I actually asked about it before I bumped into your explanation, and YT doesn't let me copy any comment from other users, although I will try it out myself later when I'm able but there's a chance that I'll misinterpret somethings) Thank you for your comment btw.

[@korkunctheterrible4302]

Also what'd happen if there were no range_example to which to assign generator_example()? it would start from the start like at every call, like you said later in your post right? but I don't remember Tim using another alias like thing, still it picked up where next() left off (4 nexts and then for loop picks up the fifth, at 09:46)

[@berkaybb5733]

Could you make a video about Web scraping by using requests and beautifulsoup modules?And maybe some decorators would be great : )

[@mufasaruleroftheanimalking1026]

It’s better to say next() consumes the list. If you printed the list y after invoking next() four times the console showed you the iterated elements don’t exist anymore in y.

[@Jschmuck8987]

After every explanation: “HOPEFULLY that KINDA makes sense”. Yes bro it makes sense ffs.

[@Tussu17]

Thank you genius!

[@rekhasurya3536]

Love your Vids Tim! keep up the good work(hope u heart this!)

[@wubangzheng]

hi i wonder any python seniors could answer my question , i just started learning python and the things i learned included all the basics (i assumed) (exp:file handling,oop,the basic commands,if,loop,tuple,dict.....).Besides,i also learned some algorithms like linked list,binary tree,stack&push.For now ,what should i do in the next step?

[@wubangzheng]

i did some python projects as well like creating a simple alien invasion game

[@Plepple]

I'm not a senior, but I think working on projects is the best way. Do webscraping with selenium, API calls with requests, build a small website with django, use pandas to work with relational data, then improve all of the IO bound tasks with asyncio

[@monicakristin8144]

tq

[@robinbreed2439]

super good

[@grantpeterson2524]

How does a for loop work on an object that is already an iterator, like map() function you showed? Does Python implicitly know if the .__iter__() method needs to be called, or if it doesn't?

[@Adedeji-v9z]

the iterator object also has an __iter__ method and a __next__ method, when a for loop works on an iterator, it calls the __iter__ method of the iterator object, the __iter__ method of the iterator object returns self (the iterator itself), why: since the iterator object is already an iterator it makes sense for the __iter__ method to return the iterator object, after that it calls the __next__ method on the iterator object getting next element in the iterator, Hope that's clear

[@mohamedelzend2337]

what is that code editor tim using ?plzzzzzzz

[@georgianabhishek3561]

Please make a pygame video explaining sprites

[@ncmathsadist]

the object returned by open("foo.txt", "r") has an iterator that walks through the file a line at a time.

[@lepidoptera9337]

That's too easy for the man. He needs to make things complicated. ;-)

[@64imma]

What text editor are you using?

[@entity5678]

sublime text

[@amrsalaheldinabdallahhammo663]

Thanks genius :)

[@UgochukwuEzeani-ut6vd]

Awesome

[@lukaszno8988]

Hi Tim can you explain interface in python?

[@neerajvaradi8505]

How your code showing the run time..?

[@comedyclub333]

I think your comparison between the generator and "legacy" syntax is a bit unclear. The class based iterator seems way more inconvenient than it acutally is since you used "range" in the generator but implemented a range-like behavior from scratch in your class. When returning a range object in the _ _ iter _ _ method the class would not be that more bloated and actually useful depending on your use case. I think it could've been made more clear that a generator relies on existing iterators while the iterator class, well, does not since it is made to provide its own iterator.

[@gagansai8880]

generators need not rely on existing iterators... def upto(x): current = 0 while current

[@comedyclub333]

@@gagansai8880 Yeah, you are right. Totally forgot about the fact that for loops and while loops are interchangable. I wrote bullshit about generators relying on existing iterators. My criticism still remains that the way custom iterator classes and generators are compared is not really fair.

[@korkunctheterrible4302]

@@comedyclub333 I don't understand. Wasn't it said or implied in the vid somewhere that yield uses next() as a built in? (I am not a geek or anything, I truly don't understand and I am a 5 year old when it comes to this)

[@terryr5713]

Tim what can I do with a computer science degree except programming!? 👍👉💪

[@pabloshi4863]

Could anyone help me of how to show the [Finished in X ms] in the console?

[@SkyFly19853]

Thanks for the explanation. Btw, are you interested in making a video about Cython ( C amd C++ extension on Python ) ? Thank you in advance!

[@jonathan3488]

Yep. I have tried using cython, but encountered IDE errors and performence issues.

[@SkyFly19853]

@@jonathan3488 I see... Even so, I think it has the potential.

[@elpython3471]

Hiyo tim! Good tutorial as always! Could you think about making more c++ content, and teach us about c++ libraries?

[@WhiteDevil-yu5ry]

Hoping For Tim! To give a heart to this comment! :)

[@youssefelamrani7905]

can you do a video about testing Tim, i heard spaceX is using Python for testing

[@xx-jk1iq]

what do you mean by testing?

[@belowasmelashgebremariam]

Nice

[@belowasmelashgebremariam]

Asme Tchaikovsky climb to uucp

[@belowasmelashgebremariam]

Razed St Ed Sry egg re zed zarathustra ink

[@edcdecl]

The range function is actually xrange. Xrange was renamed to range and the old range function is gone. The xrange function stores the result in a xrange object, not an array, which is why the new range function is smaller than the old one. Also, you can just use “for x in [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]”

[@Aidanbaro]

Hi Tim

[@malanbandara]

This guy is almost like Mark Z.

[@ilyasseidkhebbach3812]

good

[@laponiec]

Why would we want to implement our won iterators? Edit: So, we don't need to create iterators, because they have been replaced with generators?

[@HarryBGamer2570]

what's that font (name?)

[@tcgvsocg1458]

Can you create a "screen recorder"app on python please