this post was submitted on 21 Nov 2024
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Python allows programmers to pass additional arguments to functions via comments. Now armed with this knowledge head out and spread it to all code bases.

Feel free to use the code I wrote in your projects.

Link to the source code: https://github.com/raldone01/python_lessons_py/blob/main/lesson_0_comments.ipynb

Image transcription:

from lib import add

# Go ahead and change the comments.
# See how python uses them as arguments.

result = add()  # 1 2
print(result)
result = add()  # 3 4
print(result)
result = add()  # 3 4 5 20
print(result)

Output:

3
7
32
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[–] NigelFrobisher@aussie.zone 7 points 1 hour ago

They chose violence.

[–] lowleveldata@programming.dev 7 points 5 hours ago

That's quite cool. But I'm not sure what's the use case for it.

[–] would_be_appreciated@lemmy.ml 15 points 6 hours ago

I assume the people freaking out about how dumb python is didn't bother to read the code and have never coded in python in their life, because the behavior here is totally reasonable. Python doesn't parse comments normally, which is what you'd expect, but if you tell it to read the raw source code and then parse the raw source code for the comments specifically, of course it does.

You would never, ever accidentally do this.

...you'd also never, ever do it on purpose.

[–] shotgun_crab@lemmy.world 22 points 8 hours ago

This is some javascript level shit

[–] arisunz@lemmy.blahaj.zone 43 points 10 hours ago (1 children)

I fucking hate this, thanks OP

[–] xavier666@lemm.ee 3 points 54 minutes ago

How do I delete this part of the python documentation?

[–] bdonvr@thelemmy.club 136 points 14 hours ago (9 children)

IMO comments should never ever be parsed under any circumstances but I probably don't know enough to really speak on this

[–] jedibob5@lemmy.world 58 points 13 hours ago

No, your intuition is correct, this is extremely cursed.

[–] perviouslyiner@lemmy.world 36 points 13 hours ago* (last edited 10 hours ago) (1 children)

Seen in a code review (paraphrased):

image of a program which is estimating the size of an array by counting how many lines of source code were used to construct it

"Why does this break when you add comments in the middle?"

[–] bleistift2@sopuli.xyz 10 points 12 hours ago (3 children)

Why would python even expose the current line number? What’s it useful for?

[–] raldone01@lemmy.world 16 points 9 hours ago* (last edited 9 hours ago)

On a serious note:

This feature is actually very useful. Libraries can use it create neat error messages. It is also needed when logging information to a file.

You should however never ever parse the source code and react to it differently.

[–] Dicska@lemmy.world 11 points 11 hours ago

You underestimate the power of us, print debuggers.

[–] hackerwacker@lemmy.ml 10 points 12 hours ago (1 children)

Why wouldn't it? Lots of languages do. In C++ you have __LINE__.

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[–] crusa187@lemmy.ml 2 points 7 hours ago

+1 to that!

[–] ahal@lemmy.ca 2 points 7 hours ago

Ignoring lint issues comes to mind as an at least somewhat reasonable use case.

[–] bjorney@lemmy.ca 9 points 12 hours ago

The add function in the example above probably traverses the call stack to see what line of the script is currently being executed by the interpreter, then reads in that line in the original script, parses the comment, and subs in the values in the function call.

This functionality exists so when you get a traceback you can see what line of code triggered it in the error message

[–] Badland9085@lemm.ee 3 points 11 hours ago

One case where I find it useful, tho it operates in a more limited way, is code in block blocks within code comments in Rust, which are also printed out in the generated documentation. They essentially get ran as part of your unit tests. This is great for making sure that, eg, your examples left in code comments actually work, especially if they’re written in a way that functions like a unit test.

[–] peereboominc@lemm.ee 1 points 10 hours ago

Some languages use the comments to generate documentation. Something like

// function to add two numbers func Add(num1 int, num2 int)

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[–] MrPoopyButthole@lemmy.world 68 points 12 hours ago

That's disgusting

[–] datavoid@lemmy.ml 2 points 6 hours ago
[–] RichardoC@lemmy.world 52 points 12 hours ago

Thank you, I hate it

[–] scrubbles@poptalk.scrubbles.tech 63 points 14 hours ago (1 children)

checks the community to make sure I'm in programmer humor

Yeah that checks out

[–] raldone01@lemmy.world 22 points 14 hours ago* (last edited 14 hours ago) (1 children)

You know that this is acutally working right??? 😊

[–] scrubbles@poptalk.scrubbles.tech 11 points 13 hours ago

Yup, just one of those posts that could of course work in either

[–] embed_me@programming.dev 31 points 13 hours ago (2 children)

As if I needed more reasons to start away from python

[–] Chais@sh.itjust.works 15 points 12 hours ago

You can so stupid shit in any language. I admit Python doesn't exactly make it difficult. A bit like JS, but different.

[–] bjorney@lemmy.ca 8 points 11 hours ago (1 children)
[–] verdigris@lemmy.ml 4 points 10 hours ago* (last edited 7 hours ago) (1 children)

Being able to get the line number is very different from comments being parsed.

Edit: didn't realize this was custom code built to be cursed.

[–] bjorney@lemmy.ca 11 points 10 hours ago* (last edited 10 hours ago) (1 children)

You should look at how OPs example works first maybe

The python interpreter isn't parsing comments, the add() function is just getting the current line number from the call stack context, and using a regex to spit out the numbers to the right of the "#" on the current executing line of the source code.

[–] verdigris@lemmy.ml 3 points 7 hours ago

Yeah fair I was just assuming this was standard library, I see your point now.

[–] Ephera@lemmy.ml 39 points 13 hours ago (1 children)
[–] OsrsNeedsF2P@lemmy.ml 19 points 12 hours ago

Yup, the function actually goes and finds the code that calls it and parses the comment.

Disgusting.

[–] doeknius_gloek@discuss.tchncs.de 32 points 14 hours ago (3 children)

This does not actually work, right? Right?

[–] FourPacketsOfPeanuts@lemmy.world 27 points 12 hours ago* (last edited 12 hours ago) (1 children)
[–] tetris11@lemmy.ml 10 points 12 hours ago
[–] justcallmelarry@lemmy.dbzer0.com 42 points 13 hours ago* (last edited 13 hours ago) (1 children)

The add() function (that is available in the source code) basically uses some built in debugging tools to find out where in the code the function is called, and then parses the comment from the file and uses it for adding stuff.

I’ve never tried (becuse why would you…) but something similar can probably be built in any interpreted language

It’s not something Python does by design

[–] N0x0n@lemmy.ml 10 points 13 hours ago* (last edited 13 hours ago) (4 children)

Thanks :) ! Could you tell me what use case/purpose such function can have from a dev perspective?

[–] bjorney@lemmy.ca 9 points 12 hours ago

This stuff is normally used for creating human readable error messages. E.g. printing the line of your code that actually set off the exception

[–] McWizard@lemmy.zip 4 points 11 hours ago

We actually use method comments for user documentation as well. Only on specific business methods, but it's nice to have a good comment for the dev and a tooltip for the user at the same time.

[–] vort3@lemmy.ml 6 points 13 hours ago

I'd say nothing that can't be achieved by docstrings.

[–] justcallmelarry@lemmy.dbzer0.com 5 points 13 hours ago* (last edited 13 hours ago) (1 children)

This specific use case? To make a meme, mainly ¯\(ツ)

As for the components: Parsing comments have been used for stuff like type hints / formatting / linting, tho generally not at run time (afaik).

The tooling for finding out where something is called from can be used to give a better understanding of where things go wrong when an exception happens or similar, to add to logs.

I would say that in general you don’t need either functionality except for certain edge-usecases

[–] N0x0n@lemmy.ml 3 points 12 hours ago* (last edited 11 hours ago)

Thank you ! 😄

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[–] FourPacketsOfPeanuts@lemmy.world 38 points 14 hours ago

Every day further from god's light etc...

[–] LolaCat@lemmy.ca 21 points 14 hours ago

I feel sick

[–] davel@lemmy.ml 8 points 12 hours ago (1 children)

What? There is no lib module.

$ python3.13 -c 'import lib'
Traceback (most recent call last):
  File "<string>", line 1, in <module>
    import lib
ModuleNotFoundError: No module named 'lib'
$
[–] b34k@lemmy.ml 11 points 11 hours ago (1 children)

OP wrote this add() function and has provided their own lib module in the source code.

[–] davel@lemmy.ml 17 points 11 hours ago

Oh, so it’s not Python that’s cursed.

One of Python’s design philosophies is—or at least was—“we are all consenting adults here.” If you really want to turn Python into Brainfuck, the interpreter isn’t going to stop you.

[–] WILSOOON@programming.dev 6 points 13 hours ago

Why, just why

[–] muntedcrocodile@lemm.ee 6 points 14 hours ago

Makes sence if u think about it. We use comments as docstrings that the interpreter has an understanding of. Python lets u fuck with its internals (at least in an immutable manner) so why not fuck with comments.

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