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Python Is Eating the World

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Re: Python Is Eating the World

#721

Post by CydeWeys »

batbomb wrote: post #696
CydeWeys wrote: post #685

Earlier quoted context omitted.

Here's some rational "hate" for Python then. I just returned to Python for the first time in a little while to collaborate on a side project and ran into a few tricky-to-debug errors that caused a fair bit of lost time. Know what the errors were? In one case, I was iterating over the contents of what was supposed to be a list, but in some rare circumstances could instead be a string. Instead of throwing a type error,…

okay, so use type annotations and mypy --strict

It's not my project; I'm just a collaborator. My experience has been that a very tiny minority of Python code out there is written in this style, so unless you're only starting projects from scratch, you can't benefit from it.

Re: Python Is Eating the World

#722

Post by sreque »

CydeWeys wrote: post #714
sreque wrote: post #712

Earlier quoted context omitted.

I still don't think you quite understand what's going on here. Python wouldn't create a new variable in this case. I It would re-assign the value represented by the variable you already assigned once. I agree that it would have been better if Python had explicit variable declarations (this is one of the few things I think Perl got right.). On the other hand, Ruby made this same mistake. If you wrote this code in Java…

I don't understand why you're accusing me of being irrational. These seem like very rational problems to have with Python. They literally caused me bugs that cost me time to deal with that I wouldn't have faced in other languages. You're also assuming that I don't have the same problems with Ruby or JavaScript. I do. The exact same critique could be made of them as well, but they're not the subject of this thread; Py…

My bad. I didn't realize you were against all dynamic languages in particular. FWIW I prefer Java and static types as well, but as far as scripting languages go, I think Python is pretty great.

Re: Python Is Eating the World

#723

Post by sreque »

winstonewert wrote: post #716
sreque wrote: post #712

Earlier quoted context omitted.

I still don't think you quite understand what's going on here. Python wouldn't create a new variable in this case. I It would re-assign the value represented by the variable you already assigned once. I agree that it would have been better if Python had explicit variable declarations (this is one of the few things I think Perl got right.). On the other hand, Ruby made this same mistake. If you wrote this code in Java…

> I still don't think you quite understand what's going on here. Python wouldn't create a new variable in this case. I It would re-assign the value represented by the variable you already assigned once. Uh. no. he typoed the reassignment, so it wouldn't re-assign the value. > So, of three of the most popular dynamic languages, Python, Ruby, and Javascript, none of them would have helped you catch this kind of error a…

Ah my bad. I think I would have understood it more if he included the typo in his example.

Re: Python Is Eating the World

#724

Post by jcranberry »

hydandata wrote: post #640
Ensorceled wrote: post #436

Holy Crap! What a lot of irrational, hyperbolic hate for Python. I think everybody should spend their first couple of years working in Fortran IV on IBM TSO/ISPF. No dependency management because you had to write everything yourself. Or maybe [edit: early 90's] C or C++ development where dependency management meant getting packages off a Usenet archive, uudecoding and compiling them yourself after tweaking the config…

"It is a poor workman who blames his tools — the good man gets on with the job, given what he's got, and gets the best answer he can." —Richard W. Hamming[0] I have rarely "chosen" to use Python at work, but it has never failed to get the job done. [0] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2041981/

I don't think Python is a bad language but that quote is a pretty ridiculous response to criticism when the discussion on this article is a far cry from people blaming failures on Python/Python tooling.

Re: Python Is Eating the World

#725

Post by winstonewert »

sreque wrote: post #723
winstonewert wrote: post #716

Earlier quoted context omitted.

> I still don't think you quite understand what's going on here. Python wouldn't create a new variable in this case. I It would re-assign the value represented by the variable you already assigned once. Uh. no. he typoed the reassignment, so it wouldn't re-assign the value. > So, of three of the most popular dynamic languages, Python, Ruby, and Javascript, none of them would have helped you catch this kind of error a…

Ah my bad. I think I would have understood it more if he included the typo in his example.

He did. But that just illustrates why this kind of bug is so annoying, its hard to spot.

Re: Python Is Eating the World

#726

Post by jldugger »

CydeWeys wrote: post #701
_coveredInBees wrote: post #695

Earlier quoted context omitted.

Your 2nd error isn't possible in Python, so I'm not sure what you did there. Regarding the first, sure, it is a bug that was annoying to catch. But, having an `Iterable` interface in Python is also really neat and useful if used responsibly. If you're programming regularly in Python, you are accustomed to the tradeoffs that come with a dynamic programming language and no static types, and you can still avoid issues l…

I didn't explain the second one well. Here's some exact code. group_keys = ... if not isinstance(group_keys, list): groups_keys = [ group_keys ] So rather than listifying the non-list variable, it was creating a new variable. The cause of this bug is that Python doesn't distinguish between declaring new variables and overwriting existing ones.

Well, this should have been caught as an unused assignment in static analysis. A whole ton of languages allow this situation, so I'm not gonna ding Python too hard for that one.

However, here's a related but different python gotcha:

    if foo(a):
        v = list(bar(a))
    for i in v:
        print i
In this example, v is only defined inside the if. Due to python's limited scopes, v is also valid outside the if, but only has an assignment when foo(a) is True. When foo(a) is false, the for loop throws an NameError. And yes, a coworker wrote code that accidentally implemented this antipattern, albeit much more spread out in the code base.

This is clearly a bug in the code, yet no static analysis tools I've tried have successfully discovered it. There's a bug in pylint that's been marked WONTFIX because it requires a wildly different implementation. At a language level, it feels weird that if blocks aren't a scope level for new variables. If you want to reference v outside the if loop, declare / assign it outside the loop first.

Re: Python Is Eating the World

#727

Post by cc81 »

mnky9800n wrote: post #706
_coveredInBees wrote: post #695

Earlier quoted context omitted.

Your 2nd error isn't possible in Python, so I'm not sure what you did there. Regarding the first, sure, it is a bug that was annoying to catch. But, having an `Iterable` interface in Python is also really neat and useful if used responsibly. If you're programming regularly in Python, you are accustomed to the tradeoffs that come with a dynamic programming language and no static types, and you can still avoid issues l…

Maybe they could write unit tests to make sure what's being passed is lists and strings. But that's probably crazy.

That would not catch the bug if the input is not under is control.

You could as well say "Just check if the object is a string" in the method, which would work but the point was rather that it is difficult to notice if you did not think about it. Compared to other languages that would crash or not compile instead.

Re: Python Is Eating the World

#728

Post by takeda »

CydeWeys wrote: post #685
Ensorceled wrote: post #436

Holy Crap! What a lot of irrational, hyperbolic hate for Python. I think everybody should spend their first couple of years working in Fortran IV on IBM TSO/ISPF. No dependency management because you had to write everything yourself. Or maybe [edit: early 90's] C or C++ development where dependency management meant getting packages off a Usenet archive, uudecoding and compiling them yourself after tweaking the config…

Here's some rational "hate" for Python then. I just returned to Python for the first time in a little while to collaborate on a side project and ran into a few tricky-to-debug errors that caused a fair bit of lost time. Know what the errors were? In one case, I was iterating over the contents of what was supposed to be a list, but in some rare circumstances could instead be a string. Instead of throwing a type error,…

Python is a dynamic language, that's what dynamic languages do, you don't have a type checker but have greater flexibility, but you don't have to settle on that, you can actually use mypy and annotate types and get best out of both worlds.

> And another one, I typoed a variable name as groups_keys instead of group_keys (or vice-versa, I don't remember). Instead of just throwing an error, Python happily went along with it, used an uninitialized value, and then all the logic broke.

This isn't what Python would do, if the variable was undefined Python will throw an error, so you must have defined it with this name or you're misremembering what have happened.

Re: Python Is Eating the World

#729

Post by JJMcJ »

Ensorceled wrote: post #436

Holy Crap! What a lot of irrational, hyperbolic hate for Python. I think everybody should spend their first couple of years working in Fortran IV on IBM TSO/ISPF. No dependency management because you had to write everything yourself. Or maybe [edit: early 90's] C or C++ development where dependency management meant getting packages off a Usenet archive, uudecoding and compiling them yourself after tweaking the config…

Better yet, punch cards.

Re: Python Is Eating the World

#730

Post by flyinglizard »

gcthomas wrote: post #489
flyinglizard wrote: post #348

Earlier quoted context omitted.

Python’s lack of typing means the IDE heavily uses heuristics. It’s nowhere near as good as Intellisense on C#. Take refactoring a variable name as an example.

The "heuristics" are down to Python being _dynamically_ typed, not it's lack of typing, so the type can't be known until run-time. Python is actually _strongly_ typed.

Sorry, I meant lack of static typing, not the lack of any typing.
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