[python] Why does PEP-8 specify a maximum line length of 79 characters?

Why in this millennium should Python PEP-8 specify a maximum line length of 79 characters?

Pretty much every code editor under the sun can handle longer lines. What to do with wrapping should be the choice of the content consumer, not the responsibility of the content creator.

Are there any (legitimately) good reasons for adhering to 79 characters in this age?

This question is related to python coding-style pep8

The answer is

Much of the value of PEP-8 is to stop people arguing about inconsequential formatting rules, and get on with writing good, consistently formatted code. Sure, no one really thinks that 79 is optimal, but there's no obvious gain in changing it to 99 or 119 or whatever your preferred line length is. I think the choices are these: follow the rule and find a worthwhile cause to battle for, or provide some data that demonstrates how readability and productivity vary with line length. The latter would be extremely interesting, and would have a good chance of changing people's minds I think.

Keeping your code human readable not just machine readable. A lot of devices still can only show 80 characters at a time. Also it makes it easier for people with larger screens to multi-task by being able to set up multiple windows to be side by side.

Readability is also one of the reasons for enforced line indentation.

I am a programmer who has to deal with a lot of code on a daily basis. Open source and what has been developed in house.

As a programmer, I find it useful to have many source files open at once, and often organise my desktop on my (widescreen) monitor so that two source files are side by side. I might be programming in both, or just reading one and programming in the other.

I find it dissatisfying and frustrating when one of those source files is >120 characters in width, because it means I can't comfortably fit a line of code on a line of screen. It upsets formatting to line wrap.

I say '120' because that's the level to which I would get annoyed at code being wider than. After that many characters, you should be splitting across lines for readability, let alone coding standards.

I write code with 80 columns in mind. This is just so that when I do leak over that boundary, it's not such a bad thing.

I believe those who study typography would tell you that 66 characters per a line is supposed to be the most readable width for length. Even so, if you need to debug a machine remotely over an ssh session, most terminals default to 80 characters, 79 just fits, trying to work with anything wider becomes a real pain in such a case. You would also be suprised by the number of developers using vim + screen as a day to day environment.

Printing a monospaced font at default sizes is (on A4 paper) 80 columns by 66 lines.

Here's why I like the 80-character with: at work I use Vim and work on two files at a time on a monitor running at, I think, 1680x1040 (I can never remember). If the lines are any longer, I have trouble reading the files, even when using word wrap. Needless to say, I hate dealing with other people's code as they love long lines.

Since whitespace has semantic meaning in Python, some methods of word wrapping could produce incorrect or ambiguous results, so there needs to be some limit to avoid those situations. An 80 character line length has been standard since we were using teletypes, so 79 characters seems like a pretty safe choice.

I agree with Justin. To elaborate, overly long lines of code are harder to read by humans and some people might have console widths that only accommodate 80 characters per line.

The style recommendation is there to ensure that the code you write can be read by as many people as possible on as many platforms as possible and as comfortably as possible.

because if you push it beyond the 80th column it means that either you are writing a very long and complex line of code that does too much (and so you should refactor), or that you indented too much (and so you should refactor).

Questions with python tag:

programming a servo thru a barometer Is there a way to view two blocks of code from the same file simultaneously in Sublime Text? python variable NameError Why my regexp for hyphenated words doesn't work? Comparing a variable with a string python not working when redirecting from bash script is it possible to add colors to python output? Get Public URL for File - Google Cloud Storage - App Engine (Python) Real time face detection OpenCV, Python xlrd.biffh.XLRDError: Excel xlsx file; not supported Could not load dynamic library 'cudart64_101.dll' on tensorflow CPU-only installation Upgrade to python 3.8 using conda Unable to allocate array with shape and data type How to fix error "ERROR: Command errored out with exit status 1: python." when trying to install django-heroku using pip How to prevent Google Colab from disconnecting? "UserWarning: Matplotlib is currently using agg, which is a non-GUI backend, so cannot show the figure." when plotting figure with pyplot on Pycharm How to fix 'Object arrays cannot be loaded when allow_pickle=False' for imdb.load_data() function? "E: Unable to locate package python-pip" on Ubuntu 18.04 Tensorflow 2.0 - AttributeError: module 'tensorflow' has no attribute 'Session' Jupyter Notebook not saving: '_xsrf' argument missing from post How to Install pip for python 3.7 on Ubuntu 18? Python: 'ModuleNotFoundError' when trying to import module from imported package OpenCV TypeError: Expected cv::UMat for argument 'src' - What is this? Requests (Caused by SSLError("Can't connect to HTTPS URL because the SSL module is not available.") Error in PyCharm requesting website How to setup virtual environment for Python in VS Code? Pylint "unresolved import" error in Visual Studio Code Pandas Merging 101 Numpy, multiply array with scalar What is the meaning of "Failed building wheel for X" in pip install? Selenium: WebDriverException:Chrome failed to start: crashed as google-chrome is no longer running so ChromeDriver is assuming that Chrome has crashed Could not install packages due to an EnvironmentError: [Errno 13] OpenCV !_src.empty() in function 'cvtColor' error ConvergenceWarning: Liblinear failed to converge, increase the number of iterations How to downgrade python from 3.7 to 3.6 I can't install pyaudio on Windows? How to solve "error: Microsoft Visual C++ 14.0 is required."? Iterating over arrays in Python 3 How do I install opencv using pip? How do I install Python packages in Google's Colab? How do I use TensorFlow GPU? How to upgrade Python version to 3.7? How to resolve TypeError: can only concatenate str (not "int") to str How can I install a previous version of Python 3 in macOS using homebrew? Flask at first run: Do not use the development server in a production environment TypeError: only integer scalar arrays can be converted to a scalar index with 1D numpy indices array What is the difference between Jupyter Notebook and JupyterLab? Pytesseract : "TesseractNotFound Error: tesseract is not installed or it's not in your path", how do I fix this? Could not install packages due to a "Environment error :[error 13]: permission denied : 'usr/local/bin/f2py'" How do I resolve a TesseractNotFoundError? Trying to merge 2 dataframes but get ValueError Authentication plugin 'caching_sha2_password' is not supported Python Pandas User Warning: Sorting because non-concatenation axis is not aligned

Questions with coding-style tag:

Method Call Chaining; returning a pointer vs a reference? 80-characters / right margin line in Sublime Text 3 Cannot find reference 'xxx' in __init__.py - Python / Pycharm How to stick <footer> element at the bottom of the page (HTML5 and CSS3)? Simple way to create matrix of random numbers Is calling destructor manually always a sign of bad design? Count all values in a matrix greater than a value Iterate through a C++ Vector using a 'for' loop Which comment style should I use in batch files? Dictionaries and default values Error retrieving parent for item: No resource found that matches the given name '@android:style/TextAppearance.Holo.Widget.ActionBar.Title' Private vs Protected - Visibility Good-Practice Concern Java naming convention for static final variables What's the best way to convert a number to a string in JavaScript? Python style - line continuation with strings? For a boolean field, what is the naming convention for its getter/setter? Conveniently map between enum and int / String Why should I use var instead of a type? Is nested function a good approach when required by only one function? Getter and Setter? Boolean checking in the 'if' condition Why use def main()? How can I set multiple CSS styles in JavaScript? What is the standard Python docstring format? Checking for NULL pointer in C/C++ How to comment/uncomment in HTML code Code line wrapping - how to handle long lines cleanest way to skip a foreach if array is empty Coding Conventions - Naming Enums Creating an empty list in Python pythonic way to do something N times without an index variable? Should I use `import os.path` or `import os`? Python `if x is not None` or `if not x is None`? typeof !== "undefined" vs. != null Best way to check for nullable bool in a condition expression (if ...) What is the purpose of wrapping whole Javascript files in anonymous functions like “(function(){ … })()”? Using true and false in C Setting top and left CSS attributes How do I write a RGB color value in JavaScript? What is the most effective way to get the index of an iterator of an std::vector? Is it a bad practice to use an if-statement without curly braces? Advantages of std::for_each over for loop Jquery - How to get the style display attribute "none / block" Function names in C++: Capitalize or not? Why use prefixes on member variables in C++ classes Naming Conventions: What to name a boolean variable? #pragma once vs include guards? C++ getters/setters coding style Declaring multiple variables in JavaScript Is it a good practice to place C++ definitions in header files?

Questions with pep8 tag:

what is trailing whitespace and how can I handle this? How do I set the maximum line length in PyCharm? What is PEP8's E128: continuation line under-indented for visual indent? Should I use "camel case" or underscores in python? Python `if x is not None` or `if not x is None`? Pylint, PyChecker or PyFlakes? Why does PEP-8 specify a maximum line length of 79 characters?