Do variable names matter for AI code completion? (2025)
50 comments
·July 25, 2025Groxx
gnulinux
Do you still have this problem if you add a comment before declaring the variable like "Note: thingsById is not a dictionary, it is an array. Each index of the array represents a blabla id that maps to a thing"
In my experience they under overvalue var names, but they value comments even more. So I tend to calibrate these things with more detailed comments.
DullPointer
Curious if you get better results with something like “thingsByIdx” or “thingsByIndex,” etc.?
yakubov_org
When GitHub Copilot suggests your next line of code, does it matter whether your variables are named "current_temperature" or just "x"?
I ran an experiment to find out, testing 8 different AI models on 500 Python code samples across 7 naming styles. The results suggest that descriptive variable names do help AI code completion.
Full paper: https://www.researchsquare.com/article/rs-7180885/v1
amelius
Shouldn't the LLMs therefore train on code where the variable names have been randomized?
Perhaps it will make them more intelligent ...
jerf
No. Variable names contain valuable information. That's why humans use them too.
AIs are finite. If they're burning brainpower on determining what "x" means, that's brainpower they're not burning on your actual task. It is no different than for humans. Complete with all the considerations about them being wrong, etc.
JambalayaJimbo
LLMs do not have brains and there is no evidence as far as I know that they "think" like human beings do.
datameta
Right. Inherent information complexity goes down as all metadata is stripped from the variable name and the value has to be re-contextualized in a fresh logical chain every time.
amelius
Training them on randomized var names doesn't mean you should do it deliberately during inference ...
Also, I think this is anthropomorphizing the llms a bit too much. They are not humans, and I'd like to see an experiment on how well they perform when trained with randomized var names.
fenomas
LLMs do see randomized identifiers, whenever they encounter minimized code. And you can get a bit of an idea how much they learn, by giving an LLM some minimized JS and asking it to restore it with meaningful var names.
When I tried it once the model did a surprisingly good job, though it was quite a while ago and with a small model by today's standards.
knome
if you train them on randomized names, they'll also suggest them.
better to not, I think.
empath75
They're trained on plenty of code with bad variable names.
But every time you make an AI think you are introducing an opportunity for it to make a mistake.
dingnuts
No, they're more likely to predict the correct next token the closer the code is to identical to the training set, so if you're doing something generic short names will get the right predictions and if you're doing something in a problem domain, using an input that starts the sequence generation in a part of the model that was trained on the problem domain is going to be better
k__
It's kinda funny that people are now taking decades of good coding practices seriously now that they work with AI instead of humans.
roxolotl
I was talking to a coworker about how they get the most out of Claude Code and they just went on to list every best practice they've never been willing to implement when working previously. For some reason people are willing to produce design documentation, provide comments that explain why, write self documenting code and so on now that they are using LLMs to generate code.
It's the same with the articles about how to work with these tools. A long list of coding best practices followed by a totally clueless "wow once I do all the hard work LLMs generate great code every time!"
kingstnap
"Context engineering" + "Prompt Engineering":
1. Having clear requirements with low ambiguity. 2. Giving a few input output pairs on how something should work (few shot prompting). 3. Avoiding providing useless information. Be consicise. 4. Avoid having contradictory information or distractors. 5. Break complex problems into more manageable pieces. 6. Provide goals and style guides.
A.K.A its just good engineering.
nemo1618
Time for Hungarian notation to make a comeback? I've always felt it was unfairly maligned. It would probably give LLMs a decent boost to see the type "directly" rather than needing to look up the type via search or tool call.
socalgal2
It was and still is
https://www.joelonsoftware.com/2005/05/11/making-wrong-code-...
Types help but they don't help "at a glance". In editors that have type info you have to hover over variables or look elsewhere in the code (even if it's up several lines) to figure out what you're actually looking at. In "app" hungarian this problem goes away.
hmry
I remember thinking this post was outdated when I first read it.
"Safe strings and unsafe strings have the same type - string - so we need to give them different naming conventions." I thought "Surely the solution is to give them different types instead. We have a tool to solve this, the type system."
"Operator overloading is bad because you need to read the entire code to find the declaration of the variable and the definition of the operator." I thought "No, just hit F12 to jump to definition. (Also, doesn't this apply to methods as well, not just operators?) We have a tool to solve this, the IDE."
If it really does turn out that the article's way is making a comeback 20 years later... How depressing would that be? All those advances in compilers and language design and editors thrown out, because LLMs can't use them?
selimthegrim
I wonder if LLMs grok multiple dispatch
ssalka
The names of variables impart semantic meaning, which LLMs can pick up on and use as context for determining how variables should behave or be used. Seems obvious to me that `current_temperature` is a superior name to `x` – that is, unless we're doing competitive programming ;)
yakubov_org
My first hypothesis was that shorter variable names would use fewer tokens and be better for context utilisation and inference speed. I would expand your competitive programming angle to the obfuscated C challenge ;)
Macha
The problem is, unless you're doing green field development, that description of what the existing desired functionality is has to be somewhere, and I suspect a parallel markdown requirements documents and the code with golfed variable names are going to require more context, not less.
quuxplusone
"500 code samples generated by Magistral-24B" — So you didn't use real code?
The paper is totally mum on how "descriptive" names (e.g. process_user_input) differ from "snake_case" names (e.g. process_user_input).
The actual question here is not about the model but merely about the tokenizer: is it the case that e.g. process_user_input encodes into 5 tokens, ProcessUserInput into 3, and calcpay into 1? If you don't break down the problem into simple objective questions like this, you'll never produce anything worth reading.
ijk
True - though in the actual case of your examples, calcpay, process_user_input, and ProcessUserInput all encode into exactly 3 tokens with GPT-4.
Which is the exact kind of information that you want to know.
It is very non-obvious which one will use more tokens; the Gemma tokenizer has the highest variance with process|_|user|_|input = 5 tokens and Process|UserInput as 2 tokens.
In practice, I'd expect the performance difference to be relatively minimal, as input tokens tends to quickly get aggregated into more general concepts. But that's the kind of question that's worth getting metrics on: my intuition suggests one answer, but do the numbers actually hold up when you actually measure it?
quuxplusone
Awesome! You should have written this blog post instead of that guy. :)
r0s
The purpose of code is for humans to read.
Until AI is compiling straight to machine language, code needs to be readable.
deadbabe
Variable names don’t matter in small scopes.
rented_mule
It certainly can matter in any scope. `x` or even `delay` will lead to more bugs down the line than `delay_in_milliseconds`. It can be incredibly frustrating to debug why `delay = 1` does not appear to lead to a delay if your first impression is that `delay` (or `x`) is in seconds.
deadbabe
You will have exactly the same problem if delay_in_milliseconds is actually misnamed and the delay is measured in seconds.
Comments lie. Names lie. Code is the only source of truth.
r0s
The scope of the cognitive effort is the total context of the system. Yes it matters.
Sohcahtoa82
It'd be interesting to see another result:
Adversarially named variables. As in, variables that are named something that is deliberately wrong and misleading.
import json as csv
close = open
with close("dogs.yaml") as socket:
time = csv.loads(socket.read())
for sqlite3 in time:
# I dunno, more horrifying stuffrobertclaus
Nice to see actual data!
OutOfHere
Section names (as a comment) help greatly in long functions. Section names can also help partially compensate for some of the ambiguity of variable names.
Another thing that matters massively in Python is highly accurate, clear, and sensible type annotations. In contrast, incorrect type annotations can throw-off the LLM.
qwertytyyuu
lol why is SCREAM_SNAKE_CASE out performing
Obviously yes. They all routinely treat my "thingsByID" array like a dictionary - it's a compact array where ID = index though.
They even screw that up inside the tiny function that populates it. If anything IMO, they over-value names immensely (which makes sense, given how they work, and how broadly consistent programmers are with naming).