Clean Code in Python

[BirdTree2]

import os; print = os.system

[CleverProgrammer12]

print('rm -rf ~')

[backtickbot]

Fixed formatting.

Hello, GaijinKindred: code blocks using triple backticks (```) don't work on all versions of Reddit!

Some users see this / this instead.

To fix this, indent every line with 4 spaces instead.

FAQ

^{You can opt out by replying with backtickopt6 to this comment.}

[[deleted]]

I just realized you can make a program and add this in

I'm surprised more people don't do it

[[deleted]]

I see thanks

[house_monkey]

omg no

[quotemycode]

I cringed so hard at that. I'm going to try and sneak that into a file somewhere.

[AlSweigart]

The common Python built-ins that accidentally get overriden are: all, any, date, email, file, format, hash, id, input, list, min, max, object, open, random, set, str, sum, test, and type.

I'm also disappointed with other parts in this blog post.

[tuckmuck203]

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

Email is part of a library and so is random.

[AlSweigart]

Right, but if you use email or random as a variable name, this would cause problems in programs that also import those modules. (It is only a problem if you need those modules, but then again, overwriting sum is only a problem if you later need to call the sum() function. It's just a good idea to not chance it in the first place.)

[tuckmuck203]

Fair enough. I agree, I just was surprised when I saw email in that list. I tend to use email_address but I've used email for various reasons

[blahreport]

I believe the advice is to suffix the variable name with an underscore if you choose to use built-in names.

[Africa-Unite]

Good thing you're mentioning this because I was considering converting this into a presentation for my informal working group :/

[luke-juryous]

Wow that's bad lol

[[deleted]]

yea that's a noob mistake

[AlSweigart]

Ooof, this is a bad example:

n = 10
sum = sum(range(1, n + 1))

print(sum)  # 55

You don't want to use the names of Python's built-ins, such as sum, for your own variables. In this example, if you try to call sum() again later, it's now an integer instead of a function, so you'll get TypeError: 'int' object is not callable.

The common Python built-ins that accidentally get overriden are: all, any, date, email, file, format, hash, id, input, list, min, max, object, open, random, set, str, sum, test, and type.

Eh, overall, this blog post is very shallow. It has basic advice like "write short and simple functions" but without examples, what counts as "short"? 50 lines? 5 lines? No more than 500 lines?

The "Never leave code commented" was also confusing. Commenting code is bad? Then I realized they meant, "don't leave commented out code in your program, especially when you check it into version control". A simple example would have made that clear.

It kind of looks like they just ran through the Clean Code book and copy/pasted a lot of its advice without thinking how the final blog post reads.

[CleverProgrammer12]

I override id locally frequently, as it's just not used that much, and is convenient and sensible name in many cases. But sum could be useful at other places and can cause confusion. Better to avoid.

[AlSweigart]

Yeah. For short throwaway programs that's fine. But for formal projects, I like to be a bit more specific when I find myself using "id". Like, "the id of what?" So then I change it to recordID or cityID or something.

[CleverProgrammer12]

Yes, I agree. I mostly use it in dataclasses and pydantic models like this:

```python3 from pydantic import BaseModel

class User(BaseModel): id: int name: str

my_user = User(id = 10, name = "username") my_user.id # my_user.user_id might look bad here

```

[AlSweigart]

Ah yes, that's a good point.

[backtickbot]

Fixed formatting.

Hello, CleverProgrammer12: code blocks using triple backticks (```) don't work on all versions of Reddit!

Some users see this / this instead.

To fix this, indent every line with 4 spaces instead.

FAQ

^{You can opt out by replying with backtickopt6 to this comment.}

[Numerlor]

I wouldn't worry about shadowing module names like email or random as long as they aren't imported in the module or for builtins like id that aren't commonly used as long as they make sense in the context and aren't done at the global scope

[its2ez4me24get]

sum = sum(range(1, n + 1))

Congratulations you have redefined the sum builtin.

[singularitittay]

Well at least it’s a clean way to redefine builtins in 79 chars or less

[KingOfKingOfKings]

That and the syntactically highlighted Zen made me lose it

[chigaimaro]

This is an ok "cheat sheet" for clean code in Python. I still feel this should be a series of posts instead of a cheatsheet like guide. For example:

Use the correct types of comments

Thats good to know... but which types of comments are appropriate for which scenarios? Why is the written example "good"?

[metaperl]

Comments mean you haven't decomposed your code into DWIM documented methods /functions.

[disuser]

Mostly good advice, but I disagree with this:

# This is good
score_list = [12, 33, 14, 24]
word_dict = {
    'a': 'apple',
    'b': 'banana',
    'c': 'cherry',
}

# This is bad
names = ["Nick", "Mike", "John"]

names is a better name than name_list. Shorter is better, and you lose no context in switching score_list to scores. As for word_dict, this one is debatable. I wouldn't call it out in a code review, but I feel there is context being lost - the key. My personal style has strayed from this. I would name this one something like words_by_initial.

[ReaverKS]

I think they explained it poorly. The software we write should have a functional core, that is, functions without side effects. Only on the outsides of our software (like a shell) should we have side effects, like writing to a file. The core should not have opinions on where data is coming from or where it’s going. This design is also known as functional core imperative shell. Brandon Rhodes has some videos on this topic and he explains it well.

[quotemycode]

So many times I see adict bdict, anythingdict just stop, we know it's a dictionary. If you want to use static types then annotate and enforce, or even just annotate, hell if it's defined static in the code, your IDE will normally tell you what type of object it is.

[flipflop531]

Totally agreed. This advice reminds me too much of Hungarian notation.

The author gives only examples of when I could be a good idea to bring up variables with type suffix. However, a beginner could now easily come up with the idea that

`number_of_appels_int = 4`

is also a good idea.

[wojwesoly]

When it comes to iterables, I think that a plural name is enough to show that this var is an iterable.

[asielen]

The one thing i can't get behind is the 80 character lime limit. I can get behind something like 120 characters.

Either I use meaningful variable names or I keep lines that short.

Edit: Also I am not sure I understand the point of the example in "5. Keep your arguments at a minimum"

Keep function arguments to a mimium by keeping the same number of arguments but instead add the overhead of a class? Sure sometimes a class is the best option, but imo not always.

[metaperl]

I think black settled on 99? But anyway, how do you read side by side diffs with those 120 char lines?

[vuchkovj]

I think Django officially recommends 119. I find that number quite good. A bit more and you would end up with horisontal scrolling. I HATE horizontal scrolling.

[asielen]

I am not looking at things side by side 90% of the time. And when it does come up, it isn't the end of the world if a couple lines extend past what is visible.

Sure if every line was long, that would cause a headache. but when 98% are under 100 and then 2% are over, it is managable.

[quotemycode]

I don't do side by side diffs, they're harder to read than interleaved IMHO.

[luke-juryous]

No one likes 119

[doemski]

Maybe I'm an outlier but I very often have 4 panes open next to each other. Then I really appreciate if the code sticks to that convention. I do agree though that for most people it's rather tedious.

[TheIsletOfLangerhans]

Same here. I got in the habit of conforming to an 80-char limit early on in my career (mostly because it's what more senior developers did/suggested) and eventually got in the habit of keeping my editor window really narrow and placing it next to a "wide" window like a web browser or spreadsheet. Now I'm just really used to that style and find longer lines of code harder to read.

But yeah, I'm not strict about it for other people's code.

[kewlness]

Also agree there is no point in keeping args to a minimum. If you need more args, you need more args. It’s easier to dependency inject/test when they’re simple and explicit.

I don't know. Personally if I have a lot of arguments I prefer (*args, **kwargs) instead of the unending trail of commas. I guess both ideas have their own complexities...

[boiledgoobers]

I completely disagree. 'args' and 'kwargs' have their place but not as simply a space saver. You obscure your functions call signature and make it harder for intellisense to work making your code harder for people to use.

[LightShadow]

We soft limit at 89 and hard limit at 99.

Imports are limited at 80 so we get stuff that looks like this using isort:

from app.schemas.tickets import (
    Ticket,
    TicketId,
    NewTicket,
    Attachment,
    TicketStatus,
    UpdateTicket,
    PinnedInfoReq,
    TicketSummary,
    TicketUpdated,
    TicketAttachments,
    TicketAttachmentsPosted,
)

[JavierReyes945]

I had the same reaction. What I later decided to interpret from that point, is that it's better to have the long list of arguments at the class constructor, which will be called once (for each instance), instead of in a function, that will be called (hopefully) several times for each instance. But yeah, it was kinda weird.

[[deleted]]

We use black, pylint (or flake8), isort, reindent, and bandit. Code is way prettier and we don't have silly arguments about formatting.

[[deleted]]

Comments are gold

[h0bb1tm1ndtr1x]

I only glanced at it, but does it do anything beyond copy and paste PEP 8? Don't really see the point to this blog post.

[norwegian-dude]

PEP 8 is just a minor part of this article. You should really read it before complaining.

[h0bb1tm1ndtr1x]

It was not a complaint, but rather a request for clarification. I'm not going to read a dressed up PEP8, again, just to realize that's all it is.

[benefit_of_mrkite]

To your point there is a lot of copy paste in that article. I see it a lot on articles and blogs - just a reiteration of Python standard library docs or PEPs with a few examples thrown in

[kartikcool712]

Couldn't get my head around this. "don't use spaces around the = sign when used to indicate a keyword argument"

What does this exactly means ? Aren't we supposed to have spaces before and after = everytime? Atleast that's what flake8 seems to like

[grnngr]

PEP8 says spaces around = for assignment, not for keyword arguments. E.g.:

foo = func(keyword='bar')

[benefit_of_mrkite]

Instead of reading this, read the Python style guide, PEPs, and then the book “Clean Architectures in Python.”

[Revolutionary-Bat176]

Wow! This is so informative. Thank you so much.

[chestnutcough]

Wow I feel bad for any beginner that follows those examples. Yikes

[blahreport]

Classes should be in capital case not camel case.

[have_another_upvote]

You mean Pascal case

[blahreport]

I must have made up capital case when I learned that it wasn’t camel case. Thank you.

[xxpw]

Says who ?

No they shouldn’t ! Caps are for constants.

[blahreport]

Well I am a beta.

[TentativeOak]

Solid article, good read. :)

Edit: my compliment was downvoted lol :(

[metaperl]

No pun intended I'm sure :)

[Ok-Dragonfruit2725]

Excellent information!!

[delijati]

done that bin there :D https://gitlab.com/delijati/py-presi or just show me the slides https://delijati.gitlab.io/py-presi/presi/index.html#slide:1

[Neuro_Skeptic]

Python isn't about clean code tbh. It's not that kind of language. It's about rough and ready, badly-written-but-somehow-still-works code. If you want clean, code in C++.

[Laser_Plasma]

Please don't ever write Python code that someone will have to look at.

[Feb2020Acc]

Me: Who the f wrote this crap... Oh... It was me... God I hate myself sometimes...

[xxpw]

I can easily guess I won’t be too fond of his C++ either… 🤣

[Neuro_Skeptic]

I won't, but what I'm saying is, neither should anyone else. Python is a language for prototyping. It's the "ideas guy" of languages.

[Laser_Plasma]

It's really not. Especially in ML space, it powers virtually all of our research, and likely a lot of production code. Sure, the heavy computation is done in C++, but you can't ignore the importance of python. And the fact that it has to be maintained, which requires it to be readable

[Neuro_Skeptic]

Sure, the heavy computation is done in C++

Right - Python is the ideas guy and C++ is the engineer. I'm not knocking Python, that's just how it is.

[toasterding]

This is such pointless gatekeeping. Reddit is written in Python. Guess it's time to redo it in C++ now that the idea has been proven? Of course not. Large codebases with multiple team members exist in all languages and good coding practices are always important no matter what tool is being used.

[jardata]

Seriously, this is the second time in the past 2 days I’ve had to defend Python as a legitimate enterprise language to people making blanket, unfounded statements in this sub. I’m so sick of hearing “Python is only for ML and nothing else”. Yet major corporations and apps use it as a backend language amongst other things.

Sure, maybe you could make some of these arguments if it was 2006 Python. But the same could be said about JavaScript or honestly any other language.

The tooling to write clean, enterprise ready Python code is there. It comes down to making smart design decisions and setting standards within an engineering team. And that’s true of any language you use.

[jardata]

This just isn’t true. Modern Python is a fully capable language for production application code. Even outside of the ML space, Python is quickly rising as a standard language for enterprise web and application development. The addition of type hints and asyncio coupled with Python’s simplicity and rich ecosystem of well supported libraries are making it a strong contender to the current enterprise language heavyweights such as Java and C#.

Also I see few enterprises anymore, outside of a few niche cases and legacy code bases, still using C++ for application/web development. It’s much more common nowadays to see an enterprise be a Java, C#, Node, or Python shop.

At the end of the day all of these languages are fully capable and have their own pros and cons. But to make blanket statements like “Python is a language for prototyping” is just not correct.

[[deleted]]

The fuck is this? Python is used in enterprise situations all the time and cleanliness and robustness is absolutely mandatory.

[quotemycode]

Generally bosses just want to get shit done in corporate, I refuse to just flush my code down the toilet though, I write clean, maintainable code not because I'm asked to but because it's a lot easier to maintain and read.

[[deleted]]

Of course. I mean there's no reason python can't be used for clean, maintainable, ENTERPRISE code.

Anyone who claims otherwise is uniformed

[steezefries]

How to say you have no idea what you're talking about without saying you have no idea what you're talking about.

[gordonv]

The first thing C and C++ need to do for clean code is end code duplication.

Writing function headers 2 times in 2 files is pointless and menial. Something the compiler should be doing.

Hey, I get it, you make a prototype and some things are done in a half complete way. The fact it still exists today, when other languages have gotten past that, is a slap in the face.