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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.
# First we have to import comment_arguments from arglib
# Sadly arglib is not yet a standard library.
from arglib import comment_arguments
def add(*args, **kwargs):
c_args, c_kwargs = comment_arguments()
return sum([int(i) for i in args + c_args])
# Go ahead and change the comments.
# See how they are used as arguments.
result = add() # 1, 2
print(result)
# comment arguments can be combined with normal function arguments
result = add(1, 2) # 3, 4
print(result)
Choosing lib as the name for my module was a bit devious.
I did it because I thought if I am creating something cursed why not go all the way?
Regarding misinformation:
I thought simply posting this in programmer humor was enough.
Anyways, the techniques shown here are not yet regarded best practice.
Decide carefully if you want to apply the shown concepts in your own code bases.
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
Because it doesn’t seem like a useful feature. The only occasion I imagine this could be helpful is with logging to the console to track when the function breaks, but even then - still trivial to replace.
Can we just clarify that you mean that comments should never be parsed by the language engine. There are valid annotation systems, but the goal is alway to ensure that one passable can never impact the other.
Imagine if here a comment could create a syntax error! This is even worse for runtime scripting languages like python.
Sure, but let’s just clarify that this is someone going out of their way to create this problem, using Python’s ability to read it’s own code.
Basically, you can load any text file, including a source code file, and do whatever you want with it.
So, a function can be written that finds out whatever’s calling it, reads that file, parses the comments, and uses them as values. This can also be done with introspection, using the same mechanism that displays tracebacks.
capability is fine. Conflation is stupid. You can also use code to erase itself, but thinking that’s a good idea is generally wrong. But to remove that, you also remove the general ability to erase files.
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.
This isn’t standard python. lib is not in the standard library. Python also doesn’t have any special variables where it stores comments, other than __doc__ which stores a docstring. If I had to guess, add is reading the file/REPL via __file__.
It’s a string, although sometimes Python conflates the two. The recommended way to make a multi-line comment is to just make a multi-line string and just don’t use it.
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
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
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.
You should look at how OPs example works before forming an opinion.
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.
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.
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IMO comments should never ever be parsed under any circumstances but I probably don’t know enough to really speak on this
No, your intuition is correct, this is extremely cursed.
The
addfunction 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
Seen in a code review (paraphrased):
“Why does this break when you add comments in the middle?”
Why would python even expose the current line number? What’s it useful for?
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.
Why wouldn’t it? Lots of languages do. In C++ you have
__LINE__.Because it doesn’t seem like a useful feature. The only occasion I imagine this could be helpful is with logging to the console to track when the function breaks, but even then - still trivial to replace.
You underestimate the power of us, print debuggers.
Can we just clarify that you mean that comments should never be parsed by the language engine. There are valid annotation systems, but the goal is alway to ensure that one passable can never impact the other.
Imagine if here a comment could create a syntax error! This is even worse for runtime scripting languages like python.
Sure, but let’s just clarify that this is someone going out of their way to create this problem, using Python’s ability to read it’s own code.
Basically, you can load any text file, including a source code file, and do whatever you want with it.
So, a function can be written that finds out whatever’s calling it, reads that file, parses the comments, and uses them as values. This can also be done with introspection, using the same mechanism that displays tracebacks.
Conveniently Python keeps the comments around. 😄
It’s quite useful to parse comments and generate documentation from them, either as plain old hypertext or in your editor with LSP.
That sounds fine if you have something reading the file independently. But the actual executable code should not be able to access its own comments.
Comments aren’t normally accessible unless you (independently) open and read the source code file as you would with any arbitrary file.
capability is fine. Conflation is stupid. You can also use code to erase itself, but thinking that’s a good idea is generally wrong. But to remove that, you also remove the general ability to erase files.
Comments should be removed before shipping.
Well now that causes breakage two dependencies down the line. Good luck with that. 😅
Python is an interpreted language but for a compiled language absolutely (and obviously).
I guess there could be just a script before deployment.
+1 to that!
Some languages use the comments to generate documentation. Something like
// function to add two numbers func Add(num1 int, num2 int)
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.
Ignoring lint issues comes to mind as an at least somewhat reasonable use case.
This isn’t standard python.
libis not in the standard library. Python also doesn’t have any special variables where it stores comments, other than__doc__which stores a docstring. If I had to guess,addis reading the file/REPL via__file__.Is __doc__ storing a comment or just a text string?
It’s a string, although sometimes Python conflates the two. The recommended way to make a multi-line comment is to just make a multi-line string and just don’t use it.
This does not actually work, right? Right?
Anakin:
Anakin:
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
Thanks :) ! Could you tell me what use case/purpose such function can have from a dev perspective?
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
Thank you ! 😄
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
I’d say nothing that can’t be achieved by docstrings.
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.
they have to import a separate library to do this, it’s not a part of standard python, and this post is basically just misinformation
deleted by creator
checks the community to make sure I’m in programmer humor
Yeah that checks out
You know that this is acutally working right??? 😊
Yup, just one of those posts that could of course work in either
This is an affront to nature. Comments shouldn’t even make it past the scanner.
Why, just why
because OP wanted upvotes, this isn’t actually part of python in any way, it’s using a custom library to do it.
Yeah. This post was made to show off something cursed I created.
I have already updated the repo to make it more obvious this is not standard Python. I will do the same with the post.
Every day further from god’s light etc…
I feel sick
Implementation of the
add()function is here: https://github.com/raldone01/python_lessons_py/blob/main/lib.pyYup, the function actually goes and finds the code that calls it and parses the comment.
Disgusting.
It is now directly in the notebook in the latest version: https://github.com/raldone01/python_lessons_py/blob/v2.0.0/lesson_0_comments.ipynb
As if I needed more reasons to start away from python
Do you stay away from C++ too? You can do this there too
https://en.cppreference.com/w/cpp/utility/source_location/line
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.
You should look at how OPs example works before forming an opinion.
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.
Yeah fair I was just assuming this was standard library, I see your point now.
You can so stupid shit in any language. I admit Python doesn’t exactly make it difficult. A bit like JS, but different.
That’s disgusting
What? There is no
libmodule.OP wrote this add() function and has provided their own lib module in the source code.
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.
I have updated the repository. Just clone it.
The lib module was written by me. Actual implementation code is here: https://github.com/raldone01/python_lessons_py/blob/v2.0.0/arglib.py
I fucking hate this, thanks OP
How do I delete this part of the python documentation?
Thank you, I hate it
That’s quite cool. But I’m not sure what’s the use case for it.
To make bugs less traceable, I guess.
This is some javascript level shit
It’s actually kind of nice to see this as a JS developer.
Not like, “Oh wow this is neat!”
But like, “Finally the golden child, Python, also has some fucked up shit”