Python Typing - Type Hints & Annotations

Welcome back to another video! In this video, I'll be covering content from the typing module in Python like type hints and annotations. The typing module allows you to add types to a bunch of different things like variables and parameters. This can help with better documentation making it easier for others to read the code.
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📄 Resources 📄
Typing Documentation: docs.python.org/3/library/typ...
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⭐️ Timestamps ⭐️
00:00 | Overview
01:52 | Typing Module
04:00 | Type Annotations
05:34 | Static Code Analysis (mypy)
07:01 | Function Annotations
8:30 | List Type
10:12 | Dict Type
10:55 | Set Type
11:23 | Custom Types
13:17 | Optional Type
14:33 | Any Type
15:06 | Sequence Type
17:07 | Tuple Type
18:14 | Callable Type
21:38 | Generics
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⭐️ Tags ⭐️
- Tech With Tim
- Typing Module
- Python
- Annotations
- Type Hints
- Generics
⭐️ Hashtags ⭐️
#TechWithTim #TypingModule

[@gaurishgangwar]

I think Optional (at 14:10) means different than being an optional argument. Optional[bool] means that the argument can either be bool or None.

[@piraloco5864]

Kind of, your explanation on the optional type is 100% true, but you can still use it to represent optional arguments, since it means that if you dont pass the argument the type checker will accept it.

[@rabinadk1]

I was about to comment the same. Optional type is kind of confusing to most of the people. It just means additionally None.

[@martonturbuk3060]

Hi there, I came here to comment on this recent video, so I get a bigger chance of you reading this. I just wanted to thank you for all the work that you did put in these videos. I watched several of your longer videos (The Complete Python Course For Beginners for example) and they are really good. You helped a lot of people to learn, and gain knowledge, for free. Keep up the good work, and thank you.

[@bencipherx]

@@techwithtim8893 is that ur WhatsApp number?

[@UrBigSisKey]

That's thoughtful of you ... :)

[@Saitama-ur3lq]

ah! the definitive edition of typescript for python is here lol

[@soupnoodles]

Hey, thank you so much! Pretty helpful video, keep making these man :)

[@rossli8621]

Dude I just fell in love with your tutorial videos.

[@sethutrun]

Love the python videos!! Thank you so much

[@shikharpathak8510]

How amazing it is... Like there is always a lot to learn. Thanks for taking us along ❤️

[@TechWithTim]

Thanks for watching!

[@shikharpathak8510]

Lots of love and gratitude❤️

[@danielcrone9553]

Thanks for the great explanation! It'd be also good to add how people generally indicate more library-specific types like df in pandas, class, numpy, path variables.

[@PeceniJaguar]

You just use the Class that creates that object, e.g. `data: pd.DataFrame = pd.DataFrame(some_params_etc)`

[@pic01]

Thank you so much for this information, so helpful for me and everyone else

[@alloutofafricanpolarbears]

Thanks for the info dump. I have just recently started using this.

[@max.caimits]

From typing module docs: ❝Optional[X] is equivalent to X | None (or Union[X, None]). Note that this is not the same concept as an optional argument, which is one that has a default. An optional argument with a default does not require the Optional qualifier on its type annotation just because it is optional.❞

[@GeorgeSanger]

Add to add to this setting a argument to optional[bool] now mean that you can set output to None e.g. foo(None), now inside the function output will be None not False. And this wouldn't be caught by mypy. I do believe that part is incorrect, but very useful video otherwise

[@garfield-pro]

Thanks for explaining Union type which Tim missed out.

[@pratyushbehere3580]

Thanks, short and useful.

[@mohamedfarag9136]

Thank you very much for your explanation!

[@18something]

Optional is used more on the request payload validation, some of the fields are not always required. Not just to decorate an optional parameter

[@18something]

Types shine on facilitating validation more than documentation. Feel like you need to couple this topic with pydantic as well

[@cn-ml]

You should probably use the NotRequired type then, instead of Optional.

[@larrystone654]

Your videos are so refreshingly clear! Question: If the typing library is used for the purpose of complaining about incorrect typing, why do you need to run the program through mypy instead of just running the python program and letting *it* complain?

[@paulzupan3732]

According to the mypy documentation, an Iterable is anything that can be used in a for loop. A Sequence is anything that supports both len and __getitem__.

[@Zoronoa01]

Thank you Tim!

[@tomgreg2008]

Great video, thanks!

[@gerreyal]

Thanks Tim for the very usefull video.

[@gameacer111]

Great info Tim! Thanks! Love the videos

[@CaptainBravo87]

Great video!

[@axis2010]

As a few others have already commented, Tim’s explanation of Optional is incorrect. Optional means that the type can be None or the given type. e.g. Optional[bool] = False means that a user can pass in a value of type bool or None. I doubt Tim wants to allow the user to pass in None. The correct type should be bool = False

[@InglesConConfianza]

GREAT VIDEO!

[@squidproxy136]

amazing, thanks

[@MsOfficeLearning]

Thank for the best tutorial sir.

[@jleonardolemos]

great video, thanks!!!!

[@kens_adventures]

Thanks for this crush course while I am in the middle of my take home coding challenge for my job application

[@sushantgupta4757]

Thank you so much

[@cn-ml]

Very informative, there are lots of things to add to this video, but you covered a great base. I would however like to see corrections on the Optional type, which you seem to have misunderstood a lot. It is definitely *NOT* used for optional parameters, but for parameters that can also be None (of course you could have optional default params: "name: Optional[int]=None"). Also in the Callable type optional does not provide default parameters, but Nullable params, but you still have to provide them in the call! If you want default params in callables, you should probably use the Protocol type.

[@kingcrashplays]

This was the first thing I figured out due to the fact I come from a language like Java. Dynamically typed languages drive me insane, so whenever possible I always try to hint my variables with a specific type.

[@RanjithKumar-jo7xf]

This is really awesome ❤️❣️

[@gustavopoa]

Thanks Tim

[@kaanb9192]

this video was very helpful, since I saw some people use these type hints and annotations, I was wondering whether I am coding wrong. Turns out it is just for documentation...

[@Mdroudian]

The tabnine is badass. Sourcery is also a great extension.

[@raziyehnikookolah6107]

very useful

[@derekreed6798]

Wow, how complicated type hints are pre 3.9. Great video as I needed to know this stuff (so thanks for your time), but I'll upgrade my python before using typehints.

[@will2see]

Hi Tim, what keyboard are you using? I like the sound it makes ;-)

[@lt_academy]

well done )

[@John_Shi305]

非常感谢, thank you

[@sanjaykrish8719]

Thanks!

[@TechWithTim]

Appreciate you !

[@DanielDelFuturo]

It's amazing, I need to find how to use Type Hints on Django. When I use values like Dates, Email, Passwords, etc...

[@pianopianist5709]

I was watching your shorts video when I got this notification!

[@Absolotle]

Thank you! I didn't know that you could specify and test types like that. I noticed that when you tested the set as a sequence, (at 16:45) your set caontained ints instead of strings (you specified a sequence of str). Maybe that's the reason for the error and not the fact that you can't index a set?

[@Absolotle]

ok, I tried and and, yes - also a set of strings will produce an error

[@HubertRozmarynowski]

Thanks for the video, Tim. How would you type a list that can store both float and int types?

[@roshanyadav4459]

List[int,float]

[@andresyesidmorenovilla7888]

Hi tim, excellent video! thank you so much. I have a question, how would one go about typing a variable which is a dictionary, whose keys are all strings but whose values' types may be different (i.e int, float, bool, etc)?

[@cn-ml]

A bit late, but for people who are seeing this today: Dict[str, int | float | bool | etc]. Just use a Union of all types as a value. I personally prefer TypedDict to assign types for specific keys.

[@miguelvasquez9849]

Should i use Sequence[str] instead of List[str]? For your example [‘a’,’b’]

[@constantinci]

What about declaring types of custom classes as methods/constructors parameters?

[@WolfsInk]

And to think I'd just finished revamping my project creator code from the last video from you I'd watch... XD I wonder how well this would interact with pylint.

[@hujintaoxi]

Hi there, question about the type "tuple" that you mention at 17:05 - What if there is a tuple with a large length (thousands of elements) - do we still need to specify the expected type at each position of the Tuple ?

[@jesterflint9404]

Yes you do. But tuples are generally used in places like returning multiple values from a function. If you need 1000 elements, you should have used a list

[@garfield-pro]

Hey Tim, How do we hint the type of *args and **kwargs?

[@umeshlab987]

What software do you use for thumbnails

[@neiladriangomez]

He’s cute, smart and workaholic!

[@ianbdb7686]

He looks a fish from Nemo but I don't know which one

[@barisbasar3909]

@@ianbdb7686 lamoooo

[@splendorman7922]

x: list[list[int]] = [[2,3],[1,6]] works for me. is it because of version difference? Tried it on v3.9

[@dominikwodarczyk6714]

Also Union is pretty useful

[@fivefournino]

How would one type hint for objects you pull in from other packages? (Dataframe in-np array out, list in-praw out, etc)

[@BiologyIsHot]

Import and then put the class name ie var1: pd.DataFrame

[@ghyslainhubert139]

In my case, VS Code/Python 3.11.5, just starting the video (5:05), int x = 1 already causes an error "Expression value is unused" Pylance. If I enter x: int = "Hi", "Hi" is underlined as an error : Expression of type "Literal['Hi']" cannot be assigned to declared type "int", so : int causes an error. Like x: str = 1, I get a Expression of type "Literal[1]" cannot be assigned to declared type "str" "Literal[1]" is incompatible with "str"Pylance.

[@iluvsyphonfilter]

Hey Tim yesterday I was working on a Flask project and I noticed in the terminal that it made a GET request to a route from another project and of course it got a 404 because that route don't exist in the new project. I got scared and don't know what it could be, do you think someone got into my localhost? The IP address from the GET request was from my localhost.

[@iluvsyphonfilter]

@@techwithtim8893 Nevermind, I think that was caused by something related to telemetry in the browser or something like that, anyways now I'm keeping the resource monitor and task manager opened on the side to see if I catch something strange in my network.

[@tcgvsocg1458]

Can you do a video on "make a platformer game in python 2021" or beat them all Thx a lot

[@taharatamin3434]

Tim, create a tutorial on docker if possible

[@bencipherx]

I lost a German job interview cos of type hinting, no more is that happening again 🦁

[@bencipherx]

@Anne-[S]EX-Vlog Go to My Channel yes , it's type will be the class provided its imported or implemented in the same module

[@joseflat]

Anyone knows, how would I typehint , when I return an object of some of my classes?

[@nyscire877]

Just typehint your class name. For example, if you namedyour class "Foo" you would do something like that: def func(parameter: Any) -> Foo

[@miloventimiglia8547]

Isn't the case that if you find yourself needing static feature, you should opt in for Java? Or a more advance language? Python leads to a lot of overheads whereas in Java everything is already built in

[@UrBigSisKey]

How do you do Arrays then ?

[@DrDeuteron]

On tuple type (circa 17:40), what if my tuple is 10,000 ints? Do I need to code: x: Tuple[int, int, ....10000 times...int]? Seems Akward

[@ONLYUSEmyTOILET]

You could be specific and type it as x: tuple[(int,) * 10000] or just type it with arbitrary length as tuple[int, ...]

[@user-kk4jy5nm8g]

how should we insert persian in kivy

[@mback12000]

So whats the usefulness of type hinting - compared to just comments - if you're not using an analysis tool?

[@WillsonMock]

Does anyone know how to use a custom class definition as a type?

[@jesterflint9404]

The class name itself is a valid type.

[@prashantlawhatre7007]

14:23 So, Optional[bool] = Union[bool,None] and not because it has default value.

[@johnsmith-fk7fw]

i make it a point to make my code as hard as possible to read, like a puzzle. i call it 'davinci code' 😎

[@ahmedyousif4782]

The only time that I used types in python is when dealing with data classes

[@uKaigo]

Isn't the Optional type used only when None can be passed? AFAIK when you have an have an optional parameter you shouldn't type it with Optional unless it accepts None Also Optional[T] is the same as Union[T, None], implying this

[@ignis2982]

Yes, but that only applies if you type hint return types.

[@uKaigo]

@@ignis2982 oh, I thought it applied to parameters too, thanks

[@user-be2bs1hy8e]

12:30 But i thought at the start they've said "If you are looking to replace long string with easy command THIS IS NOT THAT VIDEO ...", but now it kind of is. ?

[@nunezkant]

What about numpy arrays ?

[@itaydvash]

What about objects I created?

[@snippletrap]

pyright reports type errors in your editor or IDE, so you don't need to run mypy

[@this-is-bioman]

This is an excellent presentation with nice large and readable font, dark background and timestamps! Python is by far the most stupid language LOL By design dynamically typed and without access modifiers, but yet people demand these features so they added type hints and use underscores for private members. How can you not love this illogical design decisions? 🤣🤣🤣

[@BRLN1]

You should have waited with this video until python 3.10 got published in a few weeks! However most stuff you present here is even with python 3.9 already deprecated!

[@freakpandor]

What if an object is a parameter?

[@murphygreen8484]

Date types?

[@anugrahtriramadhan9300]

How about iterable?

[@haohuynhnhat3881]

you can do list[bla, bla] in python >= 3.9, and in 5 years the List from typing.List will be deprecated

[@pkavenger9990]

16:51 I think it gave an error because you specified Sequence [str] but you put "int" in the function's parameter instead of a string.

[@ahmedyousif4782]

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[@sujeewarathnaweera]

i got the ad in the vid before

[@paschalokafor9043]

@16.47 minutes you should have tried a set of strings not numbers.

[@iddo-ba]

Hi

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Can we get some rust pleaseeee 🥺🥺

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[@apnagamer61]

1st comments

[@SenselessTalk]

First

[@pianopianist5709]

Yes!

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Cu

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Cu means ass in portuguese, so it's kind of weird seeing it randomly

[@Sciencedoneright]

@@kaiobatistaalmeida oh lol

[@imahumanbeing61]

m

[@Sciencedoneright]

@@imahumanbeing61 lmao

[@flaskblog3009]

cu ou seios?

[@hanyanglee9018]

Guys, rename this language as MyTython, or at least Tython.

[@PhongNguyen-jd3fw]

So this is typescript in python 😂

[@TechWithTim]

lol ya kinda feels like it

[@maqdala]

What font is that? What an L!

[@krtirtho]

"Python typings don't enforce what type should be passed/used. It's just for documentation purposes" *In other words, it's useless*

[@jigsaw2253]

No it’s not you dump

[@pablodm9]

The average junior coder agrees 👍

[@juanbetancourt5106]

the main purpose is to get the code easier to read in big projects.

[@BRLN1]

shot shoveling ... beautiful

[@krtirtho]

@@juanbetancourt5106 You really think Python is hard to read? Then reading Java is like reading machine code

[@ytsnanda]

First

[@ytsnanda]

Shout out bro plz

[@pianopianist5709]

You're second

[@ytsnanda]

No I am first@@pianopianist5709

[@BRLN1]

No you aren't

[@ytsnanda]

@@BRLN1 I am, I didn't ask your opinion. Tech with Tim knows.....