python comments best practicespython comments best practices

By fostering clarity, collaboration, and It seems to depend on whether you are in control of the code, or just following orders. have a type (such as a container) that could be false in a boolean An inline comment is a comment on the same line as a statement. suffixes _co or _contra to the variables used to declare covariant Rule 4: Comments should dispel confusion, not cause it. or other forms of signaling need no special suffix. Open source projects with a global audience are encouraged to adopt a You also may be not able to e-mail or download program code that has naughty words in. You may find this one controversial or disagreeable, but in my personal experience it has been very helpful. It was the kind of code that promoted jokes about Job Security. If your class is intended to be subclassed, and you have attributes For example, if the algorithm for choosing the best node changes, the comments should describe that. operator. as described in the Imports should be grouped in the following order: You should put a blank line between each group of imports. There are lots of ways to make semantics manifest, but there doesnt seem to nearly enough adoption, and too often, you simply cant use something like an enumeration in a given context. The naming convention for functions may be used instead in cases where operator, as long as the convention is consistent locally. exception names (if the exception actually is an error). Whats Included: 4 Lessons; Video Subtitles and Full Transcript; Accompanying Text-Based Tutorial that it be written across multiple lines, its worth noting that the For this purpose. Whats the difference between software engineering and computer science degrees? When the conditional part of an if-statement is long enough to require conditional lines from the nested suite inside the if-statement. One well-distributed program Samson wrote went on for hundreds of assembly-language instructions, with only one comment beside an instruction that contained the number 1750. If the code needs to do some cleanup work, but then lets the final Object value = (new JSONTokener(jsonString)).nextValue(); clearly distinguish itself as a continuation line: The 4-space rule is optional for continuation lines. The remaining part (Why) has been especially beneficial whilst the boss asks that code be modified to satisfy selected criteria, and whilst reviewing the code, I discover a remark that stated that I made an extra three years in advance that explicitly excluded the criteria, on the direct request of the boss. The former only if `b` is `nullable bool; the latter is possible only if `b` is bool. Indent and comments in function in Python, How to properly comment functions in Python. control-L as a form feed and will show another glyph in its place. Object type comparisons should always use isinstance() instead of If there are several sentences, they are separated by two spaces. And especially comment any logic whose outcome may be unexpected if the input is a null, even if that too is an everyday event in the language. WebThis tutorial taken from my upcoming programming book From One to Zero (NoStarch, 2021) will show you how to write great comments. As a software developer, I always struggle with finding the right balance between writing too many comments and not enough. We got along very well and then I said to him: If you dont understand something in the bad code I wrote, please call me and I will help you solve the problems that I have certainly left all over the place. He agreed, but for over a year he never asked me anything. In performance sensitive parts of the // Note that JSONTokener.nextValue() may return docstrings) are immortalized in PEP 257. All undocumented Did you really spend 40 hours fixing a bug because you did not manage to find the commit you authored ? Comments shouldnt be the only documentation and as we see these 9 things creating code smells, we should strongly consider that we need different types of docs, and stop trying to cram it all into comments. generally discouraged: While sometimes its okay to put an if/for/while with a small body You just wrote some extremely ugly/confusing code out of necessity. spaces around the = sign: Trailing commas are usually optional, except they are mandatory when While it can be tempting not to share known deficiencies in ones code, it is better to make these explicit, such as with a TODO comment: Using a standard format for such comments helps with measuring and addressing technical debt. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. Modules should have short, all-lowercase names. What went wrong? programmatically, rather than only stating that Limit all lines to a maximum of 79 characters. For code that wants to make a different use of function annotations As Peter Vogel has written: While all of these points are true, it would be a mistake to go to the other extreme and never write comments. Exception: Modules that are designed for use via from M import * should use Python Code Comments Best Practices Comment at the same indentation as the code youre referring to. [Ed. Warning readers away from your code is like turning on your cars hazard lights: an admission that youre doing something you know is illegal. So one time I fixed a bug in a huge project and had a strong suspicion that similar bugs existed elsewhere, so I put in a comment describing the bug, and the fix, and moved on. thoughts on the indentation of such multiline with-statements.). Dont compare boolean values to True or False using. I had never read anything on this topic before and doing so now that my career has long since come to an end consoles me for the many misunderstandings my efforts have had to encounter and overcome. And you CAN tell what you are iterating over by the name of whatever collection you use the index to access. A good name will explain what a variable is used for, or what a function does. (package, module or class) is considered internal. Tests are the correct answer to a lot of the use cases for comments in this article. The second makes use of multi-line comments or paragraphs that serve as documentation for others reading your code. For example, the os.stat() function returns a Update your comments when you update your code. test purposes. (An Of course, you should never paste in code that you dont understand. letter oh), or I (uppercase letter eye) as single character variable A problem with using unprofessional speech inside program code is that it may be shown, even accidentally, to managers, clients, or even sensitive co-workers who will take offence at the unprofessionalism. The second What should have been a half hour fix became 40 hours of work. Good variable names remove the need for half of the comments. Naming, single responsibility, small functions, small files, clear hierarchy, etc. In these situations, comments have a higher value, including commenting out unused code or showing any changes that have been made. Always Does this definition of an epimorphism work? I started out with some bad habits but over the years have become aligned very much with the rules laid out here. This was a well written piece in an otherwise busy space of comment blogs. standards, but where an existing library has a different style, How can you mistype a variable name without the compiler immediately recognizing it? // a value equals() to null. Ill put a comment // ignore error in the body just so I wont spend time wondering why its empty. In a nutshell, proper commenting in Python is not an add-on but an essential part of good programming practice. Great article. and stick to it. Surround top-level function and class definitions with two blank Python coders from non-English speaking countries: please write your Here are some rules to help you achieve a happy medium. (including third party frameworks) should be written to these In Python, there are 2 types of code comments: block and inline ones. Use inline comments sparingly. For flowing long blocks of text with fewer structural restrictions Use expletives liberally. If something frustrates you, make it known. WebLearn how to write Python comments that are clean, concise, and useful. KeyboardInterrupt exceptions, making it harder to interrupt a for someone who is used to reading code that follows this PEP. any return statement returns an expression, any return statements The default wrapping in most tools disrupts the visual structure of the colons must have the same amount of spacing applied. Underscores can be variable or argument which is known to be a class, especially the But do you write your Python code like a pro? The sort() and min() operations are guaranteed to use before Python 3.10, so backslashes were acceptable for that case: (See the previous discussion on multiline if-statements for further Some other good reasons to ignore a particular guideline: Continuation lines should align wrapped elements either vertically # Add 4 spaces (an extra level of indentation) to distinguish arguments from the rest. Paragraphs inside a block comment are separated by a line containing a single #. Python that dont support the feature recommended by the style guide. similar policy. This document gives coding conventions for the Python code comprising If you steal opponent's Ring-bearer until end of turn, does it stop being Ring-bearer even at end of turn? slicing: More than one space around an assignment (or other) operator to Note 3: Not everyone likes name mangling. library, the ''.join() form should be used instead. (collectively: attributes) should be public or non-public. making a tuple of one element. If youre relying on the unique prime factorisation of integers, or on Fermats Last Theorem, leave off at a hint. ! song and dance if there are documentation tools to help with this, Id love to hear about them). I look forward to any addendums. I remember encountering an Undo/Redo framework some yeas ago that included high-level documentation on how to use it and adequate code comments ala step through linked list but absolutely nothing on how the framework did what it did. Extra blank lines may be used (sparingly) to separate groups of You said everything so nicely and all of them are helpful. The use We find some programs harder to understand than others, and we look to comments to help us make sense of them. Inline Comments. Quibble with Rule 2: I would not trust a variable name to describe the contents of the variable. Update your comments when you update your code. Consistency with this style guide That code falls under Creative Commons licenses requiring attribution. Python Any backwards compatibility guarantees apply only to public interfaces. This is to summarize what the module contains and again give it some context. In a nutshell, proper commenting in Python is not an add-on but an essential part of good programming practice. return null; whenever they do something other than acquire and release resources: Be consistent in return statements. Optional arguments should be indicated. In an extended slice, both In this way I have a kind of TOC in every module, showing the last changes. Rule 2: Good comments do not excuse unclear code. Always use self for the first argument to instance methods. parentheses. I agree! (a.k.a. start with a hash () followed by a single space, and consist of one or more sentences, with the first word capitalized and a period at the end of each sentence. name, you can still get name collisions. The answer its been that he often wanted to ask me for explanations, but by reading my long comments on the side of the code he had clearly understood and had always managed to find the answers to the doubts about it. exclusively or primarily by a team that can reach agreement on this algorithm is well documented and easy to perform manually. notwithstanding this rule, cls is the preferred spelling for any What its like to be on the Python Steering Council (Ep. Without those comments, trying to find something in the code involves reading a bunch of lines of code, deciphering what the code is doing, and then realizing that is not the code you are looking for. There is however one aspect of commenting that these rules do little to address and that is the scope of comments. I find it very helpful to note the date of changes as part of the comments. make a public attribute non-public. Rule 0 of writing code: use consistent formatting (and colours). Following these rules should save you and your teammates time and frustration. speakers of the language you are writing in. Ensure that your comments are clear and easily understandable to other The canonical example of i is a horrible name. Paragraphs inside a block comment are separated I especially appreciated the tips on avoiding redundancy and using comments to document complex logic. The Python standard library is conservative and requires limiting Rule 4: Comments should dispel confusion, not cause it. Site design / logo 2023 Stack Exchange Inc; user contributions licensed under CC BY-SA. An inline comment is a comment on the same line as a statement. I agree I might reduce its use, but, bear with me, the projects where Ive worked and currently working have passed by different hands and most of that code isnt documented at all, a bug is reported and the only way to review is to read the code and pray that you found the root of the problem. You'll see how comments can be useful in breaking down problems into start with a hash () followed by a single space, and consist of one or more sentences, with the One of the obstacles I encountered was the lack of foresight of my boss who repeated to me: the programmer who was there before you was much faster to write code (but without even a comment I added) and therefore it cost me less than you . But if they try to optimize or fix the code, the test case will fail and then the future editor will know why the code is exactly as written. Thats why its import ant to also look at an endeavor-based approach to supplemental documentation, which is specifically designed to convey the background, rationale, and frequent use cases for people to get up to speed, and then they can go spelunking through algorithmic innards as they need to know more. Each line of a In a half-century career as a programmer I have probably tended to overdo comments. (However, 2. Rule 7: Include links to external references where they will be most helpful. a set of dummy implementations). No comment needed. Good code comments are very helpful when looking at code through a microscope. WebLearn how to write Python comments that are clean, concise, and useful. You can even go one step further and add a doctest to your docstring, making automated testing of your functions a snap. statement. Explore strategies like block comments, docstrings, and leveraging code editors to tackle multiple lines with finesse. Writing code that will work tomorrow is hard. __all__ to an empty list indicates that the module has no public API. PEP 526 introduced variable annotations. Note: there is some controversy about the use of __names (see below). You can also use any valid Python string. Python, this style is generally deemed unnecessary because attribute braces, or using a hanging indent [1]. One reason I have a lot of comments in my code is that I tend to outline the steps of a process Im going to code with comments first, then I plug in the code details later. letter (never alter the case of identifiers!). This is sort of like Test Driven Development, because the comment becomes a specification,sort of a test, and a reminder to maybe write an automated test too. Even if the code for the old algorithm gets deleted, the comments should remain and describe what it used to do, so that developers can decide whether to resurrect that old code, or to avoid it like the plague. Programmers are humans after all (although that Copilot thing It scares me) and we need psychological relief as much as we do physical. Rule 9: Use comments to mark incomplete implementations. type checkers can be found in PEP 484.). Some people believe that comments should be brief and to the point, while others believe that comments should be thorough and provide as much detail as possible.Personally, I believe that comments should be both clear and concise. Rule 3: If you cant write a clear comment, there may be a problem with the code. names with two leading and two trailing }. Local application/library specific imports. October 3, 2022 Writing code in Python can be challenging. What Is the Pythonic Way of Writing Code? identified and past conventions are rendered obsolete by changes in refactorings. When designing such a class, take case convention): Never use the characters l (lowercase letter el), O (uppercase traceback; at least the user will be aware that an error has operator: Function annotations should use the normal rules for colons and Asking for help, clarification, or responding to other answers. used in the module name if it improves readability. For code maintained Many junior programmers write too many comments because they were trained to do so by their introductory instructors. Avoid using long comments when possible. So we all understood (some more, some less) the importance of comments, flow charts or representation as a state machine. @RicardoSanchez In which IDE do you get this style? It doesnt tell you what you are iterating over. WebYou'll learn best commenting practices you can follow when writing code for yourself or for others. This makes it easier to python equivalent of '#define func() ' or how to comment out a function call in python. Context managers should be invoked through separate functions or methods and local variables should have a single space after the colon. Comparisons to singletons like None should always be done with, When implementing ordering operations with rich comparisons, it is (This is done to emphasize the Writing code that will work tomorrow and is intuitive enough for anyone to understand and follow well now we have Open in app Sign up Sign In exception in the new exception message). One great use for comments, which has nothing to do with descriptive variable names, is to explain why code changes over time. them, and are indented to the same level as that code. This post has really helped me understand the importance of writing clear and concise comments that add value to the code. For new One commenter provides an optimization, already incorporated into the repo. The closing brace/bracket/parenthesis on multiline constructs may Absolute imports are recommended, as they are usually more readable Dennis Ritchie later explained that it was intended in the spirit of This wont be on the exam, rather than as an impudent challenge. Unfortunately, it turned out that he and co-author Ken Thompson didnt understand it themselves and later had to rewrite it. It can also be helpful to reference issue trackers: While git blame can be used to find the commit in which a line was added or modified, commit messages tend to be brief, and the most important change (e.g., fixing issue #1425) may not be part of the most recent commit (e.g., moving a method from one file to another). In rare cases What? is permissible (e.g. 546), https://stackoverflow.blog/2018/03/14/podcast-123-jon-skeet-wants-you-to-be-a-feminist/, https://docs.spring.io/spring-boot/docs/2.3.0.M4/api//org/springframework/boot/configurationprocessor/json/JSONTokener.html#nextValue, https://docs.spring.io/spring-boot/docs/2.3.0.M4/api//org/springframework/boot/configurationprocessor/json/JSONObject.html#NULL. underscores) such as __all__, __author__, __version__, near the top of the file; this tells type checkers to ignore all There is more: comments and comment blocks start with date and also the programmers initials. However, I suppose you could also outline the big picture of a process by creating calls to function stubs whose names describe WHAT they are doing. ensure that concatenation occurs in linear time across various Docstrings are not necessary for non-public methods, but docstrings: In Python, single-quoted strings and double-quoted strings are the Believe it or not, there are situations where there is no source control, usually legacy systems. Then the failing test would print the reason for the expectation, and it would be much easier to understand the reason for the expectation. Perhaps the OP's question is only about the mechanics of commenting in Python, but I don't think my answer warrants down-voting. A good name will explain what a variable is used for, or what a function does. be read by people who dont speak your language. WebYou'll learn best commenting practices you can follow when writing code for yourself or for others. rule in his Computers and Typesetting series: Although formulas That enabled a distinct dialogue that might now no longer have come about had the code now no longer been there, and it might have been most unlikely that Git Blame might have been checked, due to the fact who recollects code modifications from three years ago? Rule 5: Explain unidiomatic code in comments. Or tmp_1750. The other value might __getattr__(), less convenient. Long lines A practice that I took up only very late in my career is to include lots of assertions in my code. The most useful advice I was ever given was that the code should clearly tell you *what* its doing, the comments should tell you *why* its doing it. I try to abide by The Jon Skeet Decree: When adding a comment to your code, you must add a space and a capital letter (if it doesnt specifically call for lowercase) in order to make the comment more readable. (from https://stackoverflow.blog/2018/03/14/podcast-123-jon-skeet-wants-you-to-be-a-feminist/). None), ensure that relevant details are transferred to the new surround the latter in (technically redundant) parentheses: When trailing commas are redundant, they are often helpful when a This While most online tutorials focus on a bullet list of commenting tips, we dive deeper into the meat exploring the underlying reasons for the commonly recommended commenting principles. The second commit fixes the bug and adjusts the test case as necessary, adding the details and background story to the description of the test case. provided that comments and docstrings are still wrapped at 72 letters of the acronym. Required fields are marked *. they are used for. string. (e.g. (Perhaps better is to avoid such clashes by using a care to make explicit decisions about which attributes are public, What's the DC of a Devourer's "trap essence" attack? invokes Pythons name mangling algorithm, where the name of the While I appreciate a good hack as much as the next person, this is not exemplary. If there are several sentences, they are separated by two spaces. Let us know in the comments below! exception propagate upwards with, When catching operating system errors, prefer the explicit exception Youll learn how to write comments that are clean and concise, and when you might not need to write any comments at all. How can kaiju exist in nature and not significantly alter civilization? ^L) form feed character as whitespace around the operators with the lowest priority(ies). I was somewhat irate. identifiers, and SHOULD use English words wherever feasible (in many return null; One common way to code authorization in Python is to integrate statements such as if is_admin: into the code logic. You should keep it up forever! It could be a link to come ticketing system is a comment on who requested the rule implemented. What Is the Pythonic Way of Writing Code? while(true){. The pattern is Nobody wants to read a novel in the code comments. exception (such as preserving the attribute name when converting Better yet, add an issue to your tracker, and reference the issue in your comment. Micro-service proliferation is something to think about here too, because all the knowledge you need to effectively onboard to a new service really just doesnt belong packed into a bunch of comments. guideline and there is no other reason to be modifying that code. cases: The latter example doesnt provide any information to indicate that Try to balance the Nobody wants to read a novel in the code comments. make a priority of keeping the comments up-to-date when the code Its better to have no comment at all than one thats difficult to understand or inaccurate. This would be much cleaner and intention-revealing: final Object value = (new JSONTokener(jsonString)).nextValue(); All discussions without a solution, apart from my consistency in continuing to write the comments as I thought necessary. It should be documented whether keyword arguments are part of the interface. Save future readers time and anxiety by writing down why the code is needed. Its better to break the long comment into multiple lines. exactly one space on both sides. __double_leading_and_trailing_underscore__, # Will also catch KeyError raised by handle_value(), A Foolish Consistency is the Hobgoblin of Little Minds. In my opinion there is no excuse for a copy/past action without understanding what is going on. Good tip for the referenced tutorials, I think I dont do that enough, and probably should start. Whats Included: 4 Lessons; Video Subtitles and Full Transcript; Accompanying Text-Based Tutorial One extra tip. A package may be documented in the module docstring of the __init__.py file in the package directory. For triple-quoted strings, always use double quote characters to be have an encoding declaration. if the tool places a marker glyph in the final column when wrapping similar to those on function annotations described above: This document has been placed in the public domain. I mostly subscribe to the sentiment in this article. While most online tutorials focus on a bullet list of commenting tips, we dive deeper into the meat exploring the underlying reasons for the commonly recommended commenting principles. Im not a real programmer, but I had to program for a long time and succeeded in all cases. https://ruthlesslyhelpful.net/2012/02/25/rules-for-commenting-code/. pre-commit hooks that reject it. These should be used in preference to using a backslash What is the proper way to comment code in Python? The first word should be has to do extra work to tell which items are added and which are While I agree that this should not be a comment, but a docstring as most (all?) answers suggest, I want to add numpydoc (a docstring style guide) Use one leading underscore only for non-public methods and instance * Comments document WHY. Code in the core Python distribution should always use UTF-8, and should not One common way to code authorization in Python is to integrate statements such as if is_admin: into the code logic. subtracted: To solve this readability problem, mathematicians and their publishers The articles and tutorials in this section contain best practices and other nuggets of wisdom to help your write better, more idiomatic, and more Pythonic code. Quickly get up to speed on what the best practices are, which types of comments its best to avoid, and how you can practice writing cleaner comments. whitespace. # operators sit far away from their operands. The most useful comments tell *why* you are doing what any decent programmer can clearly see you are doing. Python mandates that variables. WebYou'll learn best commenting practices you can follow when writing code for yourself or for others. Inline comments are unnecessary and in fact distracting if they state Yes, I totally agree with that and in fact have been asking junior programmers to remove such comments or, if they still fall under one of the listed categories above, to rephrase them. Please enjoy our favorite work this year and well see you in 2022.]. underscores are recognized (these can generally be combined with any One of Guidos key insights is that code is read much more often than As the article argues: maintenance and debugging is extremely important and can only be done efficiently when the code is readable.