[anderskaseorg]

> For example, you basically never care whether something is exactly of type list, you care about things like whether you can iterate over it or index into it.

This is an odd complaint. typing.Sequence[T] has been there since the first iteration of typing (3.5), for exactly that use case, along with many related collection types.

https://docs.python.org/3/library/typing.html

mypy isn’t perfect, but it’s sure better than making things up without any checks; you’re going to want it for all but the smallest projects.

[ReflectedImage]

You should never be using static typing with a scripting language like Python or Ruby.

Dynamically typed code is 1/3rd the size of statically typed code, that means that one developer who is using dynamic typing is equivalent to 3 developers using statically typed code via MyPy.

Since the code is 1/3rd of the size it contains 1/3rd of the bugs.

This is confirmed by all the studies that have been done on the topic.

If you use a static type checking with Python, you have increased your development time by 3 and your bug count by 3.

Static typing's advantage is that the code runs a lot faster but that's only true if the language itself is statically typed. So with Python you have just screwed up.

[bombolo]

> Dynamically typed code is 1/3rd the size of statically typed code,

This is absolutely not true.

> Since the code is 1/3rd of the size it contains 1/3rd of the bugs.

That is made up and contrary to all empirical evidence I've ever collected.

I'd be curious if you have a source, but I doubt it.

[ReflectedImage]

Anyone with experience of writing both dynamic typed and statically typed can tell you that.

Infact, you could just try it out for yourself.

But here is your internet source for this blatantly obvious fact: https://games.greggman.com/game/dynamic-typing-static-typing...

[bombolo]

I do have such experience and I really can't tell that. Which is why I wondered if anyone else was in fact saying that.

> But here is your internet source for this blatantly obvious fact: https://games.greggman.com/game/dynamic-typing-static-typing...

Ah no I meant a proper peer reviewed source. The claim that untyped code has fewer bugs is completely bonkers, so I was quite sure that no such source existed.

Why do you think microsoft, google and facebook are all in the business of typechecking python? If typechecking would actually introduce bugs, it'd be better not doing it right?

Using github for statistics is flawed. There are millions of 10 line js libraries. Yes it's easy to not make type mistakes in 10 lines. I suppose that type errors increase more than linearly with size.

[hbrn]

> The claim that untyped code has fewer bugs is completely bonkers

Not really. It is, however, quite expensive to measure, because dynamic typing really shines at the evolution of software, that is being able to respond fast to changing requirements. Legos vs play-doh: https://weblog.jamisbuck.org/2008/11/9/legos-play-doh-and-pr...

> Why do you think microsoft, google and facebook are all in the business of typechecking

A billion flies can't be wrong? Companies with unlimited amount of money are not the right place to search for good practices. Both Facebook and Google became flush with cash way before modern type obsession. Sure, once you are a multi-billion dollar company slowing down can be a good thing. But you need to get there first.

> If typechecking would actually introduce bugs, it'd be better not doing it right?

If sugar caused us to die sooner, we'd be better to eating too much if it, right? And yet, here we are.

[ReflectedImage]

"The claim that untyped code has fewer bugs is completely bonkers"

There are plenty of academic sources that will tell you that the number of bugs in a program is directly proportional to the number of lines in the program and static typing has no effect on this.

https://stackoverflow.com/questions/2898571/basis-for-claim-...

Additionally, statically typed code involves large amounts of boilerplate code in the form of abstract base classes, interfaces, generics, templating, etc. It's a very verbose code style.

It's your turn, find an academic source to backup your claim that static typing reduces the number of bugs. Cause it just isn't true.

Microsoft, google and Facebook have a lot of programmers coming from languages with static typing and want to make Python more familiar.

It's a far distance away from anything resembling good practice.

Actual Python houses typically don't use static typing.

[UncleMeat]

Not across different languages. Create a new version of Java that requires an empty line between each line containing text and bugs won’t double.

[bombolo]

Please don't reply multiple times to the same thing.

> Actual Python houses typically don't use static typing.

If you had ever developed python professionally, you'd know this to be untrue.

Also your "paper" points to a 404 page.

[ReflectedImage]

"If typechecking would actually introduce bugs, it'd be better not doing it right?"

Correct if you misapply a tool to the wrong situation you get poor or negative results.

The right tools are unit testing, integration testing, uat and automated whole system testing.

[bombolo]

That seems to completely forget the fact that libraries exist, that A LOT of bugs can happen calling libraries, and that you're not really supposed to unit test libraries, they are supposed to have their own tests.

[TrickardRixx]

Please see Raymond Hettinger's keynote on efficiently handling bugs[0]. He makes the case that static type checking is a boon for Python except for in specific programs that make extensive use of covariant and/or contravariant types.

[0] https://www.youtube.com/watch?v=ARKbfWk4Xyw

[ReflectedImage]

Increasing the time to market by a factor of 3 is never worth it.

[dragonwriter]

> You should never be using static typing with a scripting language like Python or Ruby.

You should use it where it makes sense, and not where it doesn’t. I haven’t used any of Ruby’s type checkers, but Python makes this easy enough; make what has a reason to be dynamic dynamic, and have static safety rails everywhere else.

(This is true with many “statically typed” languages that have dynamic escape hatches, too, not just traditionally “scripting” languages.)