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80 chars per line is great (wrongsideofmemphis.com)
82 points by jaimebuelta on Mar 25, 2013 | hide | past | web | favorite | 118 comments

At Google, our Python style guide dictates 80 characters with 2 character indenting [1]. Java is the only exception at 100.

Even 100 can be awkward to fit into. Lord knows I've renamed variables to avoid splitting a line on several occasions.

But what a lot of posters here seem to miss is that it isn't about the width of screens for editing, it's about the width of screens for reviewing so you need twice the real estate.

Add in doing interactive merges and you need three times the width.

This really comes down to the principle of enforcing a common style (for an organization or project). A lot of people rail against "arbitrary limits" and "arbitrary style guidelines" as it's something extra they need to learn and adds no value (according to them). I've seen people here for 6+ months again still fighting this.

Such things (IMHO) have value as it adds a reasonable level of consistency across teams, it avoids commits on files due to stylistic changes (which may or may not be automatic from IDEs, etc) and, most importantly, defuses a lot of the aesthetic-driven boneheadedness that we engineers are prone to.

The last point is really important. Otherwise you'd have engineers and groups fighting over where to put curly braces, 2 space indents vs 4, whether tabs are OK, etc--none of which actually matters.

So if you feel your creativity somehow stifled over 80 characters, I'd strongly suggest you just abosrb it, get over it and move on to things that actually matter.

[1]: http://google-styleguide.googlecode.com/svn/trunk/pyguide.ht...

Lines of > 80 characters are really the last jabs at the dying corpses of typography and taste in the digital world. Typographically proper paragraphs are not wide across, because that forces the eye to move more while reading. This is a basic fact that has been known for literally longer than we've had printing presses.

Wide lines are barbaric, and I'd go so far as to say that languages that can't be rendered comfortably in 80 character lines are nothing more the primitive tools of barbarians.

> Wide lines are barbaric

I agree utterly, and enjoy the irony that I read your comment displayed as http://i.imgur.com/iJNs9SV.jpg ... a full 258 characters ... HN could do with some responsive css to max-width comments above certain viewport widths!

The last point is really important. Otherwise you'd have engineers and groups fighting over where to put curly braces, 2 space indents vs 4, whether tabs are OK, etc--none of which actually matters.

This is probably the most insightful comment to come out of this discussion. The exact numbers aren't all that important, but having a consistent style (including line length limits - which I'm fairly sure no one will argue that there should not be a limit) and not checking in stylistic changes (or at a minimum, disentangling them from actual changes of substance) is important.

The problem is, we as programmers obsess over details (especially the closer you get to the hardware). The key is to obsess over the correct details, or obsess once and move on.

> At Google, our Python style guide dictates 80 characters with 2 character indenting

The style guide you linked to says indents are 4 spaces. I sense the question of indent size hasn't been solved at Google yet :-) I find 2 to be too little, except for XML and HTML which are naturally indented many levels and there's no way to refactor into new functions or methods.

[Edit: added quote]

So we're all staring at a wrapped lines so you can do a 3-way merge? How often do you need to merge anyways? More often than you write code? Often enough for it to be the limiting factor?

How did they do interactive merges when they were limited to 80 characters?

i concur

I've renamed variables to avoid splitting a line on several occasions

enforcing a common style

I've seen people here for 6+ months still fighting this

Or you could, you know, just treat each other as adult, responsible individuals.

Hint: rules for the sake of uniformity don't "defuse boneheadedness". They just suppress individuals, and eventually either drive them out or tame creativity, initiative, and responsibility out of them.

I mean, come on, you say that yourself! So just acknowledge that that's what you're doing. There are processes for making better software. These kinds of style guidelines are not among them.

I am unmoved by this argument. Forcing E.E. Cummings to use proper spelling and punctuation would certainly have had a detrimental effect on his poetry. The other couple billion English speakers benefit from consistency the other 99.9999% of the time. If you can't find non-syntactic ways to express your programming brilliance, creativity, initiative and responsibility, then I doubt you have all that much in the first place.

For what it's worth, E. E. Cummings most often wrote his name with proper capitalization.


Thanks, fixed.

I love how a lot of responses here are of the condescending tone of "we aren't using vt100s anymore, grandpa", as if advocates for the 80 column limit are still running VIC20s in their mom's basement. I see this argument pop up a lot against things like vi and Emacs as well.

Yes, we realize that monitors are bigger, resolutions are higher, etc ad naseum. None of that matters. What matters is code readability. So what if you can fit 120 characters in your code editing window? I can fit more than 400 across two monitors, should the new line length limit be 400? Why stop there, why not just let lines be endless and have the editor wrap them? Answer these questions, and you've answered why people still like the 80 column guideline, or even care about code formatting at all. Code is only incidentally written for machines to execute; it should be written for people to read.

Yeah, but code readability has little to do with line width. I could show you perfectly unreadable code that fits in 80 characters because it's legitimately pre-indented by 40 and has to go to one word per line or shorten variable names to fit in 80, and wonderfully easy to read code that goes out to 160 (often because of some literal data that would otherwise just increase the vertical length).

Also, it's funny to me that people talk about horizontal line length impacting readability, but never seem to talk about vertical length impacting readability as well. To me it's critical to keep related code clustered vertically as closely as possible without too much brevity: having to scroll/split view to see related pieces of code incurs a cognitive overhead. Arbitrary line breakage imposed by the 80-character limit gets in the way of that. (And don't get me started about teams that treat this as a limit instead of a guideline.)

It's critical to give programmers the tools to make their code readable (good languages with good grammar and idioms), not arbitrary restrictions that try and fail to accomplish that indirectly.

> I could show you [...] wonderfully easy to read code that goes out to 160

I'm calling this bluff. No, you can't. If you actually have evidence I'd truly love to see it.

Ridiculous line length is actually one of the most reliable code smells I know. Seeing something like that, I can virtually guarantee that it's an OOP-gone-wild mess of needless abstraction, tightly coupled data structures spread across a dozen files. It's going to be a spaghetti mess of nested if() constructs used where clean data-driven logic would have been better. It will be filled with commented-out-code. And it will probably have indentation that lies, lined up in incorrect columns waiting to fool the developer.

Clearly you feel differently. Prove it. :)


Feel free to criticize. That code has lots of shortcomings. Compromised readability due to line length is not one of them.

You can't be serious. Check lines 388-400. Now, even ignoring the fact that github itself is chopping those lines because they're too long, they're simply not meaningfully readable. The ridiculous repetition (which is the proximate cause of those awful line lengths) totally obscures the meaning.

Note all the repeated use of this weird dictionary name "my_stats[condition][strand]". This thing appears, often multiple times, on ever line of that loop. You're telling me that this couldn't be made more readable by using a simple local "stats" reference name "st"? Repetition of expressions is the sign of lazy code, it's the same kind of thought process that gives us cut-and-paste bugs.

Note likewise the repated use of "kc_stats[condition]". Same deal. Same treatment.

Note likewise the oddball commented out line (assigning a tuple of m2_ci_lo_fwd, m2_ci_hi_fwd) which is disabled without explanation. Remember my list of attendant symptoms?

And, on the design side: note the mean/median/stdev calls. Those are generally pretty well-defined properties of "sets". Why is there a "Metric" postpended to the method names needlessly? Surely the reader would understand "st.stdev()" already, right? And why do the methods take five named parameters?. That's insane -- they should take zero. It looks like this is trying to pass in some extra "stuff" (maybe to control some side effects, or to filter the data) to what should be an idempotent operation on a fixed piece of data. If you have to filter, or if the object does some extra counting or whatever, those should be set up on the data ahead of time.

This code is crap. Sorry.

Just because I'm feeling bored today, here is that same loop (around line 388) "cleaned up" to work inside 80 columns. I added a "metricGenrator" abstraction to the API because it seemed like a sane addition to clean up the "too many arguments to mean()" problem, but all other changes are is pure syntax. I dare you to argue that this isn't more readable than the original:

      my_stats = {'Modified': {'+': {}, '-': {}}, 'Control': {'+': {}, '-': {}}}
      for condition in 'Modified', 'Control':
        for strand in '+', '-':
          st = my_stats[condition][strand]
          kc = kc_stats[condition]
          kc = kc.metricGenerator(metric, ref_pos=ref_pos, trim=opts.exp_trim,
          st['mean'] = kc.mean()
          st['median'] = kc.median()
          off = st['stdev'] = kc.stdev()

          if use_se:
            kc.setOpts(ref_pos, metric, trim=0.0,
                       coverage_ceiling=opts.coverage_ceiling, strand=strand)
            off /= sqrt(len(kc._getMetricData()))

          st['spread_lo'] = st['mean'] - off
          st['spread_hi'] = st['mean'] + off
          my_report_row.extend(st['mean'], st['median'], st['stdev'],
                               st['spread_lo'], st['spread_hi'],

I don't know if this was easy or quick for you (less than an hour, in any case), but you seem to prove the parent correct: "That code has lots of shortcomings. Compromised readability due to line length is not one of them." Maybe you're simply an amazing programmer, but to jump in and refactor a small bit of code deep inside something you've never seen before proves to me that the initial code was indeed readable.

In either case, both examples are literally geometrically square, which I think drives readability more than line width. When the long lines poke out and don't relate to other long lines, it's hard to read. If all the lines are long and share structure, it's just verbose, but reasonably easy to read. With that perspective, I'd say the parent's code isn't a great example of long-line code: it doesn't demonstrate a _need_ for 160 chars; I'll agree with you.

I started typing a longer response, but honestly I think the clearest answer here is just sarcasm:

Some of us have a higher standard for "readable" code than "can be refactored so that it doesn't suck". :)

The code is illegible for a number of reasons:

* Duplication everywhere.

* No internal comments indicating the code's purpose.

* Long functions with too much nesting.

* Lack of constants.

* Indenting by 4 spaces (instead of 2).

* Lines like 316-320 and 326-335 should line break and indent after the first open parenthesis to avoid huge whitespace.

* Inconsistent line break usages for long lines.

* Line 412, for example, should line break at "ref_pos".

The code has many shortcomings, including readability due to extreme line length.

  self.opts.modified_positions_fwd = [ int(p) for p in self.opts.modified_positions_fwd.split(",") ] if self.opts.modified_positions_fwd != None else []
Without explicitly attacking Python's syntax, I had to horizontally scroll left and right multiple times to understand the entire impact of this statement.

Both yours and my claims are anecdotal. Unfortunately I don't know of many research studies, though I'm sure some has been done for this issue in typography.

You're right, those lines (and a few others in that file) aren't good. For the ones you cited, that run-on if really is too far out. If I was writing them today, I'd break it up into an if..else.

> people talk about horizontal line length impacting readability, but never seem to talk about vertical length

This is why I think it's absurd that we still use flat file text editors to code. I don't care about how functions are laid out in the file. As you said, I care about their semantic relatedness. That may vary by concern. It's almost like I want to tag each function with the features/concerns that it addresses. Then I'd like to be able to view each tag on its own, and have all its constituent parts (functions, modules, classes, etc.) laid out in a way that makes sense. Maybe that's stacked vertically, maybe side by side, or maybe something else. I'd be able to switch between views at will. Each feature branch would probably have its own view.

This would have the side benefit that a function with many tags is a new smell, but more meaningful than character or line length.

The only people I know of who are even attempting to address these issues are Brett Victor, Jonathan Edwards, and the Light Table people.

I recently switched from 80 to whatever will fit (oh, 120 or so) on certain projects.

Its an extremely personal decision because it depends on the exact interface of your skill level as a programmer in general, your skill level with that particular language, your skill level in the business problem domain, AND your own peculiarities WRT to the kind of errors you make.

Given the exact workload I'm being paid for at this time I do NOT make "line" level errors or even "small block" errors but instead get tripped up on crazy "business logic" and big architectural issues. So I am better off at this moment with longer lines showing more "big picture" than with clear little lines.

What I'm getting at is on recent projects I've been making more mistakes with "which blocks of changes need to complete transactionally/atomically based on crazy business logic without causing race conditions" rather than "I need to make it really clear I'm adding these two numbers as opposed to concatenating two strings" or whatever.

This tradeoff of width vs length varies for me, project by project based on actual requirements.

Personally I think this helps "those who come after me". If you see long complicated lines that's a warning that you should tread lightly there and there's probably something complicated at the "vertical" big picture level going on, so I had to make the "horizontal" look icky to make it fit. If I'm just squirting out blah blah code and hitting enter every 20 characters you can safely assume at the big picture there is nothing very complicated going on.

A good (fine arts oil) painting analogy is which is better, portrait or landscape canvas? Well, it depends on the scene. Maybe you personally are only commissioned to paint portraits, well then...

The better and higher resolution monitors I got the more fanatical I got about the 80 column rule. Why? Because I can split my code into vertical columns on the new fancy monitor. If code lines are 160 I can or have to constantly horizontally scroll them or live with random wrap-arounds.

Then the next up monitor I could do 3 columns, so I still stuck to the 80 column idea.

80 characters is an accident of history, an accident that should be corrected. With an 80 character limit, you need to be mindful of the length of your identifiers. You start compromising recognizability in the name of fitting the line to an essentially arbitrary length (drop a few vowels, maybe use a less precise word).

Using a width limit to coerce into indenting less is just plain silly. If you don't want high levels of indentation, put THAT in your coding guidelines. Don't rely on side effects.

This isn't about the indentation. Look at the examples. you can see that allot of his code is indented heavily.

This is about the amount of time and distance required to scan my eyes across a line to understand its meaning. How much do I have to read to understand a simple concept?

This is also about the amount of screen real-estate i have to use. We arn't programming on VT100 terminal any more, damn right. NOW I get to have the compiler output and continuous integration output to my left. The directory, class structure and documentation to my right.

I also get to split my screen to have two editors open for comparing snippets of code line by line.

Merge conflicts and diffing are hugely common operations. merges have three parallel windows open at once!

You, still, only have 80 characters to work with.

    This isn't about the indentation.
From TFA:

    Also, having the mandatory indentation whitespace increase the line width is a good visual way of minimising the nested loops in your code and suggesting, in a subtle way, to refactor anything that is indented more than about four times.

Your line from TFA is 241 characters, making it a pain to read....

yah, but I think the author is arguing side benefits.

to be fair, so am I.

The author was asserting 80 character line width was easier to read.

> 80 characters is an accident of history

So are many useful inventions.

The reason it matters is readability. News papers for example have been using columns for readability and to me that makes it easier to read.

Having the same for code is great.

I have 3 vertical monitors so I want to have as much of the code go vertically and then I split the monitor into 2 or 3 columns (vertically), I find I get much better productivity, and my eyes get less tired. I like scanning up and down not too far to the left of right.

I have not always followed this and looked at some old code with 160+ long lines in some places.

Besides terminals are still used when logging in via SSH into a server it is still nice to not to have to keep re-sizing the terminal according to whatever the largest line is.

I don't think long lines that are broken in the middle at 80 characters are more readable than single line that goes to slightly more. Readability in code is not about having a pleasantly looking paragraph (paste some code into MS Word and see how readable it is). Readability is about conveying logical structure through form. A statement is in one line because it is doing one thing.

No, but long lines that are broken intelligently so as to fit in an 80-character wide space are easier to read than a single line.

    MyObject object = MyObjectBuilderFactory.getBuilder().essentialProperty("the value").otherImportantProperty(42).specialThingyReference(someVariable).build();

    MyObject object = MyObjectBuilderFactory.getBuilder().
        essentialProperty("the value").
Or how about:

    cookies = responseObject.headers.findAll { header -> header.key == "Set-Cookie" }.collect { cookieHeader -> new Cookie(cookieHeader) }

    cookies = responseObject.headers.findAll { header ->
        header.key == "Set-Cookie" }.collect { cookieHeader ->
        new Cookie(cookieHeader) }
Just because it is one statement does not mean it has to be on one line.

I would find your first example very readable on multiple lines (it lends itself naturally to breaking up), but only if you go all the way and break on every dot. As it is, it looks asymmetric, like something an automatic word wrap would do and it is very easy to miss that last build() statement when scanning.

But second one looks like a mess either way :), partly because I am not familiar with the language, but mostly I think because brackets are opened and closed on different lines.

I'm sure you can come up with several pretty ways of breaking up every specific situation that is both aesthetically pleasing and functional (in fact I already use your first example, with slight modifications), but there is no general way that can be encoded in rulebook or indent rules of an IDE.

> I'm sure you can come up with several pretty ways of breaking up every specific situation that is both aesthetically pleasing and functional (in fact I already use your first example, with slight modifications), but there is no general way that can be encoded in rulebook or indent rules of an IDE.

Sure, but there are always edge cases not covered by the rule book or IDE. For me the rulebook should say "break lines so that no single line is > 80 chars" and leave it to the programmer to do so in an intelligent way for each scenario. Or if you want a little more conformity add some guidelines like: keep a method call on one line if possible, keep each method parameter on one line if possible, when breaking a method call over several lines vertically align each parameter (indenting when a parameter consists of a long method call itself), etc. You can cover the majority of cases. Examples are helpful.


    return calculateFirstPart(commonObject, dataObject) + 
           calculateSecondPart(commonObject, aDifferentDataObject);
instead of this:

    return calculateFirstPart(commonObject, dataObject) + calculateSecondPart(
        commonObject, aDifferentDataObject);

        "Why are all my identifier names are so long?",
            currentKnowledgeEngine, Language.English),
        "Why is this parameter here. I don't even know what it does")
instead of this:

    computerExplainToMe("Why are all my identifier names are so long?",
        currentKnowledgeEngine.selectedExplanationType, KnowledgeContext.
        getContextForEngine(currentKnowledgeEngine, Language.English), "Why " +
        "is this parameter here. I don't even know what it does")
The thing about long lines of code is that they almost always contain multiple ideas compressed into one (variable assignment, retrieval, lookups, conditionals, etc). In most programming languages we could put the whole program on one line if we really wanted to. When I see a line that is > 80 characters it makes me think I should be breaking that line up into multiple statements anyways, but depending on the language we may be saving ourselves some boilerplate or sometimes actual resources by putting it all in one line. So intelligent linebreaks are a good compromise in my opinion. We can still separate the individual expressions into readable chunks, but keep the whole expression more tightly packaged (physically and mentally) than it would be if we broke it out into multiple statements.

Just for fun, here is maybe a better way to write that second one:

    cookies = responseObject.headers.
        findAll { header -> header.key == "Set-Cookie" }.
        collect { cookieHeader -> new Cookie(cookieHeader) }

I mostly agree, but I find the effort to properly format broken long lines and to maintain the format when moving code around is sometimes too much. Most editors will indent the continuation by one position like in all your examples, but that is not always what you want (for example a nested call you'd want to indent further). So every time you move the code or copy function call it has to be reformatted manually (especially if one has a slight OCD :)).

This potentially leads to people simply breaking in an arbitrary place, making code less readable than without a break.

(Last example does look better. :))

You're assuming a proportional font, and English language keywords.

What about?...

我品 品= 我品做厂.受做().必要产("the value").别重要产(42).特别Thingy提交(任何变量).做()


饼干s= 响应品.首s.找都{首→ 首.钥匙 ≡ "Set-Cookie"}.收集{饼干首→ 新 饼干(饼干首)}

They're on one line and more people can read it than your English version.

I guess 80 chars is a rule for latin alphabet based code. A similar rule for chinese would be "whatever historically didn't fit on printed media in country of origin". :) If there are historical parallels at all that is.

I think it is not optimal to easily convey logical structure when code spans long lines left to right. If all the lines are consistently above 120 characters or so, it it is a smell test for bad code (or maybe the wrong language or framework).

Having a consistent width also means not having to rely on a randomly chosen width of the editor and then have random wrap-around code or having to resize the window horizontally or scroll horizontally when also scrolling vertically.

Most good editors will handle well multi-line splits. I use emacs I know it does, it would be silly to use MS Word to edit code.

When I started out I didn't follow the 80 column rule it is something that came with experience (also being able to afford a better monitor, paradoxical perhaps, but once I could open two windows side by side, I wanted to be able to not having to scroll either horizontally).

“80” is an accident of history, but “around 80” is not; it's a product of centuries of experience with reading.

Grab a novel. I bet the line width is closer to 60 characters. Horizontal scanning is hard on the eyes.

Luckily, most code is indented 1 to 4 levels at 2 or 4 spaces per indent. This means that typical code width is limited to be anywhere from 78 to 64 characters wide. That's 77 to 63 if you're actually going with 79 characters, which is what PEP8 et al suggest. Much closer to the 55 to 65 characters of the two or three books I just checked.

You're quite right. The ‘accident’ of 80 comes from the ability of a typewriter to space into what were usually margins.

It is the hjkl of line length.

Screw arbitrary limits.

Personally, I prefer the 120 characters per line guideline. Most code I see starts looking very ridiculous when trying to accommodate the 80 characters max width, and it starts becoming hard to follow lines when exceeding 120 characters. So, to me a soft 120 characters guideline is the nice medium between the fact that it's no longer 1980 and the need to make lines easy to read.

Also, in most cases readability has almost nothing to do with line width (in fact it can suffer greatly from too much line breakage), and everything to do with how the programmer chooses to structure their code, aided by language idioms.

I do the same thing. I set a vertical guideline to 120 characters. Depending on the codebase I'll turn on wordwrap at 120 characters too.

I like a 80 column soft limit which I usually stick to and a 120 column hard limit which I use when I feel splitting the line and indenting would harm readability.

This so much. Rather than "don't exceed 80 characters" the guidelines say "break up complex statements into multiple lines if it contains complex logic" and say that the target should be 80 - 120 chars per line.

Just for comparison, I'm reading your comment at 140 characters width and I don't have much problem with that. I like my web text to occupy most of my screen. Only if I stretch it across multiple monitors to 160+ chars per line does reading become a chore.

But it is a personal taste.

I had to fight with my team over the 80 character limit, but they eventually gave in. It works great in nearly every editing environment, and I've started trying to use it as much as possible in non-python projects as well. I can neatly fit two windows side-by-side in my IDE and read them both easily. I just can't go back to the old way of having the ends of lines hidden off-screen.

Do you code on a netbook? 2x120=140. At 7px each, which is generous (even if you are using some non-proportional font for archaic reasons or misplaced machismo) that is under 1000px wide.

I have a 27 inch monitor and still prefer an 80 character limit. It rarely forces me to mangle code and allows me to have four different files open side by side. It's especially useful for frontend development where I'm going to be editing html, css, and javascript almost all at once.

This "hurr durr, we aren't on terminals anymore" argument is dumb. You aren't arguing with crotchety old geezers or people with stupid hardware choices. Quit assuming the people who disagree with you are idiots.

With you here. I don't even know how big my monitor is, but more horizontal space just means I can open up more code windows side-by-side, which means I can see more context at once. All to the good.

I agree with the parent- in my case I use a 27" display @ 2560x1440. I split the screen in half- browser or shell on one side and Sublime on the other. So Sublime gets 1280 pixels.

With the project side panel open enough to see most of the project's directories it uses ~370px. The minimap (which I do leave open, and use, often) takes up ~50 pixels and the scroll bar for the edit window a final ~20 leaving me with 840 pixels that can show just at 100 columns. If I kill the minimap I get almost exactly 120 cols.

For me, I have no qualms about 79 cols for the limit and enjoy being able to use my windows split to half the screen and still have some breathing room around the right edge of my code. I also find it awkward to scroll horizontally to see what's going on in a long line.

2 times 120 is 240. Which at 7px each clocks in at 1680. It'll work on a desktop monitor, but probably not on a laptop.

No, but I like to keep a folder on the left-hand side with my project files. And 7px is far too uncomfortable for my ever worsening eyesight.

With the long variable/class names used these days, and the availability of clear, small fonts and 16:9 displays, 80 columns seems silly. But I'm against raising it, even to 100 columns. 100 really isn't much more than 80. And then you start to lose things like being able two view two pages of code side by side.

The other problem is that 100+ column lines are just flat out hard to read. It's hard to follow text that far across these screen. A few years ago when I was working with Objective-C I came across methods used with each variable on one line and really grew to like that.

It's similar to the way source code is laid out in books. But is that because the code is more readable that way, or is it a consequence of the layout? Books are taller than they are wide and usually have generous margins.

I use a soft-ish guideline of 100 columns per line, but I mostly code in C# at work, so normally namespace/class/try-catch is already 3 indentations, and 80 chars is simply not enough for everything.

I do my best to keep it between 80 and 100 chars. With a horizontal screen resolution of 1920 pixels, 2 pages of such code fit nicely side by side.

I think the three file views side by side image is one of the best arguments I've seen for 80 chars. But I'm predisposed to like that image, because I like 80 chars.

Or 2 files + a sidebar (using an IDE), 3-panes merge, etc...

So why not make it 60 characters? Then you could have 4 files side by side!

But seriously - I guess there is some workflow where you would like to have 3 files side by side, but I certainly have never felt like that is something I need. I would much rather have readable, verbose variable names, which I have found to be the first thing to get axed in an 80 char column setup.

Three files side by side is extremely common for those of us who have to regularly resolve merge conflicts. You put the common ancestor in the middle and the diverging changes on either side, then you edit both sets of changes in to that middle buffer.

I resolve merge conflicts as well. Every system I've ever used gives you one file with delineated chunks (<<<<, === >>>). Never once have I said "this is too difficult - I need three windows open." And even if I did say that sometimes, I can't imagine optimizing the character width of my code for that one use case.

The most definite thing that should be taken from a thread like this is that it usually boils down to personal preference. In fact I'd say that personal preference in these matters should take at least as much preference as any available emperical studies. If you're in a group, and you don't get your way in the coding standards meeting, accept it and move on. You can do it! :)

60 characters? Why, that's just not done.

The thing people miss here is the "Python related". If you need 120 characters on a line then you completely missed the "zen" of python.

Having to go beyond about 85 characters is a good indication that you probably need some refactoring in your python code. As the idiome states, "Flat is better than nested."

Your if, in an if, in an if, in a for, in a method, in a class is probably complete garbage. Even in other languages, if you are so nested that you legitimately need 120 characters then you likely need to refactor. Your code that is nested to oblivion will prevent anyone from being able to give you a thorough code review which opens you up to unnecessary risk.

This is painfully presumptuous. Generalizing others' code and constructs as "probably complete garbage" and suggesting that a 120-character line implies a "need to refactor" is either profoundly naive or grotesquely smug.

I love Python, but programming languages don't have "zen," and reality is never so ideal that an 80-character line -- in and of itself -- can ever be assumed to imply anything useful.

Thank you for making that point.

I used to work on some code that did a lot of subgraph matching. Subgraph matching in general is computationally expensive, so ideally you do it heuristically, searching for more likely elements of the subgraph you’re looking for first so you can skip over edges/vertices that have no potential as early as possible. Even then, if you’re looking for a complicated subgraph then you’re going to have a bunch of conditional logic that runs lots inside deeply nested loops one way or another.

That kind of code is often unwieldy, simply because the algorithms it implements are unwieldy. However, arbitrarily factoring out some of the inner levels into separate functions, which might have little meaning in themselves and little potential for reuse out of context, just means when you’re trying to review/update the code you need to look in more than one place to find it. On top of that, you’re also incurring a bunch of relatively heavy function calls (many parameters might need to be passed in for context) right in the middle of deeply nested code or you’re trusting your optimiser to inline them reliably.

So these days, whenever I see someone quoting dogma about how more than n levels of nesting are bad and your code needs refactoring if you hit their personal arbitrary limit, I cringe a little inside. Not all real world algorithms fit neatly into a dozen lines of code and a level or two of looping.

Long ago, I wrote Web pages to be served from OS390. Because it still enforced the 80 char limit from punch cards, I had to adhere to it, also. But no fancy editors for code directly in the machine. And when any line ran over 80, it would only render the first line of HTML. Took me hours to figure that one out.

But I never ran across anything I couldn't make decent inside those 80 characters.

I find the 80 char limit nice as a suggestion/warning, a way of saying "are you sure your approach should require lines of code this long?" So, a good way to make sure that someone is writing readable code, which is otherwise the overall goal of PEP8. But, sometimes there are lines of code that are perfectly readable, maybe even more readable, despite exceeding 80 characters, and which become less readable by doing line continuations. (I would argue that line continuations make everything less readable, almost all of the time.)

The other rule that I personally ignore, and when I'm managing a project I have my developers ignore, is the suggestion to use spaces instead of tab characters for indentation. Of course, with Python, you must use one or the other, but I prefer tabs.

In both cases, it comes down to my belief that individual coders should have the ability to customize their experience without forcing it on everyone else. When you use spaces instead of tabs, and indeed, when you use line continuations, you're forcing your (the author's) exact view of the source code on everyone you're working with. If you use tabs, and don't use line continuations, others with specific needs (2 character tabs, 4 character tabs, 8 character tabs, 60 character-width editors, 100 character-width editors, etc.) can, with any modern editor, customize their view (using variable-width tab stops, and soft line wrapping) to what they're comfortable with.

I think its a given that we'd all agree that writing portrait mode or landscape mode you still fundamentally take about the same number of square inches to do it.

One observation is a fixation on horizontal space never on vertical. If you can't make sense of the big picture without scrolling vertically then you're probably doing it just as wrong as requiring horizontal scrolling to see the little picture.

Two interesting analogies:

RISC vs CISC. Doing something RISC like with simple little operations but the order and block control are super important? Go "RISC" landscape mode. Doing something ridiculous complicated at the operation level? Go "CISC" portrait mode and only do one "weird thing" per line.

Another interesting analogy is I've been in this game since 1981 and the physical display ratio has consistently gotten shorter and fatter every year (kind of like my body, sorta). Like it or not, the style trend is that someday our display hardware is only physically going to be capable of something weird like 800 characters across and only 8 lines up and down. You might have a 10 inch tall display but if 6 vertical inches are taken up by window bars and tab bars and ribbons and 25 toolbars and a bottom status bar, well you're only getting 4 vertical inches. Doesn't matter much if you like it or not, you'd best get used to it as styles don't seem to be changing, not even the 1st or 2nd derivative of the ratio over time...

I really like the 80 character limit for readability, but I'm also a fan of what it does to git commits (and any other diffs). When I have to wrap code, say, function calls, I often use one line per keyword argument. When you have to change or add arguments later on, git recognizes that only one line -- the argument -- changed, instead of the entire function call changing.

What about other languages? I find it harder in C/C++ when I have functions with too much parameters. It's almost less beautiful to look at. Do you change parameter names to shorter ones, add usings to avoid explicitly stating the scope, tab at 2 spaces instead of 3/4, increase the line cap to 90/100?

On a semi-related subject, what about the vertical limit of the code? I often heard that a function should fit in one page, but that also depends on the screen resolution. Also, the 80 chars rule would increase the amount of line instead. How do people deal with that in general?

Yeah - I was thinking about a Java codebase I was looking at a while back that had ultra verbose variable names like "BackupCopyOfLedgerUsedInWorstCaseScenarioProjections" You couldn’t even do a simple addition in 80 characters.

This limitation seems fairly language specific, and has a lot of side effects for the rest of your style guide.

I'm ok that people don't use email/vim/sublimetext2 with splitting panes, but don't people use meld / kdiff3 for reviewing they're changes? And on my 1366x768 120-chars would be too wide to show in meld.

I much prefer colored unified diffs in my terminal (e.g. those from git) over side-by-side tools with multiple panes.


I love to work with a 79 chars per line limit.

For those using vim, I use this snippet to automatically split my window at startup:


    set colorcolumn=80 
is another nice way to keep yourself within the bounds, it also has the bonus of not being a hard limit, just a visual indication that you're overstepping

edit: (already mentioned)

When I can freely decide, I set the column indicator in eclipse to 100 and set eclipse to not enforce this limit (maximum line length=1000, never join lines). I prefer it like this because there are circumstances where longer lines make sense for me. Anyway, I try to keep lines as short as possible because I usually use a very large font for coding and have 2 files open next to each other...

In vim (appears the author is using macvim) you can use

    :set cc=81
to mark the 81st column and visually nag when you go over 80 chars

100 characters seems a pretty reasonable compromise. Keeps lines from getting too long and hard to follow, but you're not splitting lines all the time just to keep under the limit, which also reduces readability.

If you're having trouble fitting two 100 character wide files side by side, there's two things you need to do:

#1 - get a screen with a decent resolution. 1920px wide should be standard for any developer worth his salt. Yes, this means "don't develop on a 13 inch laptop screen"... you're a developer, this is the main tool to do your job, make it a decent one.

#2 - use a real font. Courier New (or whatever the corollary is on Linux/OSX) is not a real font. I prefer proggy fonts (http://www.proggyfonts.com/index.php?menu=download)... they are incredibly more compact and still very readable... you get significantly more characters on the same line.

Author here, just for reference, I use a iMac 27'' and Menlo 11 (I also have an extra screen, where I put other info, like mail)

I anyway use the same setting when I use a laptop, though is not my main workplace.

80 characters seems like such an arbitrary restriction. Once upon a time we were limited to 80 characters but we were also limited to monochrome ASCII text. Just as syntax highlighting improves readability, I think the occasional use of longer lines where appropriate improves readability - the shape of the code gives your eye additional clues about where you are in a section of code, allows you to have more lines on the screen at once, find what you're looking for faster, and isolates details that aren't crucial in getting the big picture. E.g. - inline lambdas or anonymous functions, strings, etc.

When I work on a codebase with formatting standards I try to follow them. This is 2013, though, and when I work on my own stuff I format it to get the most readability on my Macbook or 32" 1080p desktop screen, not a VT100 from 1987.

> When I work on a codebase with formatting standards I try to follow them. This is 2013, though, and when I work on my own stuff I format it to get the most readability on my Macbook or 32" 1080p desktop screen, not a VT100 from 1987.

And then someone working on your code on an eeePC will have a great time!

The options are: use smaller font size, enable word-wrap, buy a higher-resolution display (or two), use your IDE to auto-format code according to your preferences. I don't really see anybody using eeeePC for serious coding in 2013.

> use smaller font size

Makes the code harder to read

> enable word-wrap

Makes the code harder to read

> buy a higher-resolution display

Increases cost and I can't take an external on the subway/train.

> use your IDE to auto-format code according to your preferences

So, make it 80 to 120 chars per line myself

> I don't really see anybody using eeeePC for serious coding in 2013.

Because the year means sooooo much. Who are you to choose when and how I code.

> Who are you to choose when and how I code

I'm asking the same question when 80 chars limit is enforced on me.

80 to 120 char has other advantages over just screen size. It's easier to read as well. Working on a team is giving and taking of everyone's capabilities. I've had to work on teams that use odd tabbing, but I do it because that's what others use.

If you're doing a lot of development on an eeePC then line length may not be your biggest obstacle.

Who are you to choose when and how I code. eeePCs work well in commuting situations.

Visual Studio 2010 ain't quite zippy on a netbook. They are fantastic, but they do have notable limits.

Sure, but I dev in vim, linux, and the associated compiler/interpreter. A netbook is quite a handy for that type of dev.

> combined with the use of whitespace in Python, makes the code much more compact and readable

Because of Python's significant indentation is exactly why I can't stand 80 char limit. Breaking lines, causing "false" visual structure destroy's Python's readability.

Seeing more logic vertically is far more important than horizontal.

I've been on teams that choose horrible names, used strange constructs, etc. just cause they fit on 80 char. Also wasting huge amount of time getting shit under 80char. Oh, and 80 char leads to people using import from over import (to avoid fully qualified names), which introduces bugs (name conflicts) and tons of confusion / lookup time wasted figuring out "process" is from some.lib and is not local,, or the one from some.other.lib

Personally I find the splitting in the for loop much harder to read, though the smatch splitting is fine.

I would favor splitting only if you're indenting to line up with the first couple of tokens. In those cases the pattern is obvious as soon as I start reading, and my brain switches to scanning vertically. I find it jarring to have to switch from having read most of a line to suddenly scan vertically.

It seems like the example doesn't demonstrate the point that precedes it at all. Apparently in this example an 80 character limit doesn't promote re-factoring, it promotes splitting lines. Which makes the justification for 80 characters being a typical line length + 4 indentations a bit weak and 80 is back to being arbitrary.

I don't quite like the loop split, but that's because I've never like "continue the next line under the first argument of the series." It makes next lines start at inconsistent places and makes it harder to read. I usually bend that rule and follow the four space indent 90% of the time.

But I do like the loop split better than the non-split, despite the above.

I like the smatch split too. It looks like how you'd arrange bullets in a bullet list, one below the other, so you can see/scan them at a glance, without having to labor over where the next item is in a single line.

Rules are there to be broken.

I stick to 80 chars 99% of the time because long lines are more difficult to read.

But if a line ended up being 84 characters wide I wouldn't go replacing variable names or hacking a single function call onto multiple lines to fix it.

No one has died yet :-)

I hate the the 80 character limit. I never follow it, though using 2 char instead of 4 char indentation might help.

The main reason I hate it is pretty simple: I think it encourages using cryptically named variables. I find that using properly descriptive naming often leaves lines around 90 to 100 chars, particularly with 4-space indents and several arguments or a chained call. I also don't find the suggested practice of implied multi-line via unclosed parens leads to good readability in many cases.

That said, I agree there should be some limit. My usual practice is to set it at 120 chars, though I find it rare for a line to exceed 90 to 100 chars.

The only consistent method is to not wrap text at an arbitrary limit. Everyone can follow this and it is very clear. Readability may or may not be compromised. Dictating an arbitrary line width is exactly that: an arbitrary standard. If it works for you and your team, great, but ultimately it is a totally arbitrary choice.

Also, I believe that text editors are generally catching up in this regard and doing a good job of intelligently indenting code that wraps over multiple lines. This means you can choose an editor width that suits your needs rather than having it dictated by someone's arbitrary choice.

I agree that we need a limit, but in my experience 80 characters is often too limiting and sometimes causes wraps that make the code less readable instead of more readable.

I use a vim colorcolumn at 80 characters as a soft limit, but the hard limit for my projects is at 100 (or 99, to be exact). This has proven to be a nice guideline to write readable code, versus the 80 hardlimit that forces you to write short code (which sometimes is less readable than a clean & clear line with 90 characters).

The problem with 80 chars/line and Python, in particular, is list/dict comprehension. Naturally, as they replace a whole loop, comprehensions pack much information into one line. Consequently, there are many times when a list/dict-comprehension line that are clean and meaningful but had to be broken into 2 lines.

And that isn't nice.

Having a list comprehension in 2 lines is really a problem? I find very readable something like

  result = [something(value) + value * 2
            for value in values]
I mean, I prefer one line, but if it has be in two (or more lines), I don't see the problem really

Actually, with a minor tweak this gets even more readable -

    result = [something(value) + value*2
                for value in values]
I find indenting the subcaluse makes my eye flow naturally over the code. I'm normally doing this in perl, and often end up with functionalish code that looks like

    my @result = map { something($_) + $_*2 }
                   grep { valid_candidate($_) }
but the same principle seems to apply nicely to both languages.

A foolish consistency is the hobgoblin of little minds.

80 character lines is perfect. Allows me a reasonable number of splits in vim and most importantly makes diffs/code that I get in my email readable.

That being said, as with all things(especially guidelines), apply common sense liberally. Which in Python is one of the guidelines of pep8 on writing readable code.

At 80 characters, I often find myself worrying about line length more often than worrying about the problem I'm trying to solve. 120 is fine. Also, I orient my (widescreen) monitor vertically so I don't have anything side by side anyway, just top and bottom where I can see more lines of code.

It's great for a language that is not whitespace-significant. Python requires hacks like backslash just to do a line break, which makes both alternatives (with/without line break) equally ugly.

Ideally, IDEs should automatically take care of how to represent the code according to user's preferences. Also, IDEs can save files according to project's guidelines.

I like to have my font size rather large. It reduces eye and neck strain for me and makes the long days more ergonomic.

An "80 char/line" guideline is nice for that.

I mostly agree, but SQLalchemy queries and the occasional complex conditional could cause one to reconsider or start making allowances.

80 chars ought to be enough for anybody, right?

With default bells and whistles your IDE provides enabled, you'd be lucky to have a 79 char wide editing area.

There are modern options though:

1. Disable unnecessary stuff on your IDE. 2. Don't use a IDE, use a dedicated editor. 3. Don't use an editor from a VGA console. 4. Stop pretending you code on a vt100.

I see no wrong with a sensibly long line which is longer than 79, just as I see no wrong in keeping multiple parts of code visible at all times. There shouldn't be hard limits or carved to stone guidelines.

what? do programmers still layout their code using whitespaces manually? use code editors that support declarative stylesheet for layout and enable intuitive structural modification.

I prefer to be in absolute control of the layout. It's not that big a task.

what about having a limit for the number of lines, 200 lines?

In mission-critical systems line limits are common. The first public example that comes to mind is the NASA JPL C Coding Standard(http://lars-lab.jpl.nasa.gov/JPL_Coding_Standard_C.pdf). Check out Rule #25:

>Functions should be no longer than 60 lines of text and define no more than 6 parameters. [Power of Ten Rule 4]

>A function should not be longer than what can be printed on a single sheet of paper in a standard reference format with one line per statement and one line per declaration. Typically, this means no more than about 60 lines of code per function. Long lists of function parameters similarly compromise code clarity and should be avoided.

>Each function should be a logical unit in the code that is understandable and verifiable as a unit. It is much harder to understand a logical unit that spans multiple screens on a computer display or multiple pages when printed. Excessively long functions are often a sign of poorly structured code.

I agree completely with the author that readability is paramount and artificial limitations are often questionable.

Having said that, whenever this topic comes up, we always seem to fall into the same trap of comparing one dubious representation (very long lines) with another (awkward breaks to avoid crossing an imaginary limit). Beyond a token comment on not nesting too deeply, and a token reply that sometimes deep nesting really is tidier than artificially separating the inner levels somehow, we rarely consider whether what we’re representing is fit for purpose. Does it really make sense to take the basic syntax we use for short expressions like

    short_name(easy_param, other_param)
and try to apply it to longer expressions like

or something more complicated than a single function call? This leads to a debate where the most radical alternative proposed might be something like

        first_param, second_param, third_param)
If you look at well typeset mathematics, which suffers a similar problem of scalability, there are often (at least) two different conventions for representing the same mathematical expression. For example, maths set using the TeX family probably has one version designed to read neatly in-line with other text, but another version designed to be clearer when set as a standalone display that might cross several lines.

There are many tools for tidying up those displays, aligning things in logical ways. There are also conventions for breaking expressions too wide to fit on a single line, and sometimes those conventions do opposite things when setting an expression in-line to in displayed form, for example when deciding whether to leave a trailing + at the end of one line or move it to the start of the next. There is also a general idea that if you’re dealing with a lot of expressions that don’t fit, you should be looking to define self-contained parts of those expressions separately, and incorporate them indirectly using a more concise notation within the larger expressions. There are even subtle cross-references like numbering the key equations (only) and then adding a note like “by (1) and (2)” in the margin to help the reader navigate a complicated series of results. All of these ideas fit within the broader typography of setting a paper or thesis, where you still want good general readability in terms of (physical) line lengths, numbers of columns, use of tables, positioning of displayed content, and so on.

In programming, we have some of the same basic ideas, particularly separating out smaller parts of a larger whole as separate functions or variables for exposition, but we haven’t really developed the same depth of typographical conventions. Almost everything is based on the idea of taking that basic syntax that works on a single line for relatively short expressions and trying to make it work for arbitrarily large expressions across many lines with nothing but a line break and fixed tab/space characters as tools.

I think this is partly because our text-based editors typically don’t separate the meaning of our code from its layout. Even ideas like elastic tab stops, which might be everyday alignment tools in programming languages that use meaningful indentation, are still esoteric. A few functional languages promote ideas like “let x in y” or “x where y” syntax to help separate out subexpressions, but on the scale of functions separation implies creating a new self-contained function to do part of the work, which comes with its own scope, which means explicitly passing values in and out when they were already conveniently available in the all-in-one function.

I don’t see the controversy over X characters per line limits going anywhere until we get over these more fundamental problems of conflating code layout/presentation with code meaning. We need to be able to express the ideas in our programs systematically and have our editors and diff tools and code review software present those ideas in a suitable layout that adapts to both the idea itself and its context. Sadly, that’s not going to happen as long as we keep asking questions like how wide a tab stop should be, and not asking questions like whether we should even have tab stops at all.

Not being able to fit the code in 80 columns easily (for me at least) is a smell test for potential problems code.

Now it depends on languages, I am thinking of Python, C and Erlang here.

If you use too many:

is there a way to alias it to a function local name such as my_handy_function = <the above>. Maybe there isn't (again it depends on language here as well).

> I think this is partly because our text-based editors typically don't separate the meaning of our code from its layout.

You need a better editor. That is a solved problem. I like emacs the best. I imagine vi is just as good. It knows how to indent code based on the semantics. It knows you are in the middle of the list or just started a code block and does the right thing. (And I don't mess much with the default, an editor that does most thing reasonably form then on I assume whatever else it does to my code is now the new "right thing").

> A few functional languages promote ideas like “let x in y”

It kind of proves my point -- if you have functions that are going past the end of the screen, you need to think a bit about the code (also of course depending on language here, but most languages allow this). Break it up into functions. For functional languages like Erlang, they really encourage short functions that are 5-10 lines long. Use function clauses and pattern matching (with guards) to lay out the logical structure and so on.

is there a way to alias it to a function local name such as my_handy_function = <the above>

I agree, though of course a single function call is a trivial example. It would be nice if we made more use of intermediate variables for exposition to simplify complicated expressions more generally, too. But somehow this sort of idea rarely seems to get promoted whenever long lines come up in discussion. :-(

You need a better editor. That is a solved problem.

I respectfully disagree. Current editors, even the most flexible, rarely do more than automatically sorting out line breaks and indentation, and rarely provide more viewing options than collapsing blocks and jumping around to one cross reference or another. I am challenging the assumption that even the same symbols in the same order are necessarily appropriate in different contexts.

I think there is a parallel here with the idea that a variable or function name can be relatively short if it’s only used locally with the full context available, but it might be better to use a longer, more detailed name or to add full qualifiers like which package/module/scope the entity lives in if it’s going to be used more widely. This is a simple case of adaptation that many programmers would apply instinctively, but it illustrates the basic principle that using the same name/representation for an idea regardless of context isn’t always helpful.

Break it up into functions.

But at the moment, breaking something into functions for ease of presentation typically equates to breaking something into functions to establish an independent scope, to allow wider reuse, or for other non-presentational reasons.

For example, most languages offer no way to break down a moderately long pipeline algorithm into stages without separating each stage into its own function, complete with manually passing all of the context in and passing all of the results back. If many stages depend on much the same general context for that algorithm and the stages don’t make much sense outside of the algorithm as a whole, might we not consider some sort of lightweight, presentational way to split things up for better readability, without implying all the side effects and maintenance overheads of full functional decomposition?

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