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Ask HN: Why PEP8 favors using spaces over tabs for code indentation?

• csense 14y ago
  I chose spaces over tabs long before I started writing Python. The issues with tabs are: (1) Some editors will autoconvert them to spaces. Every time you switch editors, switch IDE's, edit your code on a different computer, or let someone else work on it, you have to remember to make sure your tabs are still there. (2) With tabs, your code will look different for different people. I often line up parts of adjacent lines that are symmetric, and different tab widths will interfere with this. Ditto ASCII art in comments. (3) It's hard to use tabs consistently because tabs and spaces are visually identical in most editors. (This is less of a problem in Python than other languages, because inconsistent tabs/spaces in your indentation are often caught quickly because they cause syntax errors.) (4) My mathematical mind admires systems that are designed around simple and elegant ideas. A character display embodies the following two such ideas: (a) Each location on the screen contains exactly one character. (b) There is a one-to-one mapping between the pixel contents of an 8x8 box (or however big your font is, assuming all sane people use monospace fonts for coding) and an ASCII character. (Don't get me started on Unicode. I don't understand it, don't use it, and it haven't had it do anything for me but cause bizarre problems [1].) Tabs break both of these properties. This causes cognitive dissonance and offends my sense of aesthetics. [1] http://news.ycombinator.com/item?id=4369323 http://news.ycombinator.com/item?id=4369323
• tyger11 14y ago
  Using tabs over spaces is a catastrophic misunderstanding of modern text editors. Spaces are the ONLY one-size-fits-all solution for a multi-developer environment. Text editors can be configured to SHOW a tab character visually as any number of spaces you want - without changing the code. If someone likes 3 spaces, they can see a tab character as 3 spaces; if someone else likes 8 spaces, they can show each tab as 8 spaces. Treating a tab as a "tab stop" is the mindset of a typewriter user.
  • codegeek 14y ago
    Not sure if I followed what you said. What I mean is that isnt hitting the spacebar 4 times more difficult and annoying than hitting the tab key once ? Yes you can configure tab key for any number of spaces but still the point being about hitting spacebar multiple times.
    • kudakeru 14y ago
      Modern editors generally don't require you to hit space four times. There's a "convert tabs to spaces" option so you can hit the tab key, and most of them do auto-indenting anyway.
• Rust 14y ago
  I'm no Python expert, but the only reason I can think of is a combination of developer inertia and tradition. In most IDEs, a TAB can be displayed as any number of equivalent spaces (8 being the common indent size), so if I switch back and forth between my big monitor (8) and my laptop screen (4), I can view the code with an indent relative to the width of the screen. If that code uses spaces, I'm usually stuck seeing an indent of 4 on the big screen monitor - something I find irritating because it makes it harder to visually scan and parse code quickly. So, even in Python, I always use TABs whenever I have the choice. It's just more flexible.
• runjake 14y ago
  Most editors automatically convert TABs to x number of spaces automatically, so you don't have to think about it. For example, see set expandtab in vim: http://vim.wikia.com/wiki/Converting_tabs_to_spaces http://vim.wikia.com/wiki/Converting_tabs_to_spaces
• cutie 14y ago
  The reason is that when sharing code use of tabs can lead to confusion, subtle, and not so subtle errors, especially in Python, where consistent indentation is most important. For example, one person has tabs set to the size of 8 chars and writes a lengthy script. A second person comes along with tabs set to 5 chars and makes changes. The indentation could well be wrong because they see the same file differently. Sometimes you get lucky and you get errors immediately, but other bugs can lurk... like the second statement under an if block for example. Should it be included in the if or not? Bug. Therefore, tabs aren't worth the trouble they can potentially cause. Never mix them with spaces either. Also, using spaces is not difficult in a modern editor. You don't have to actually type four spaces each level. You set tabs as 4 spaces in the prefs and then every time you hit the tab key you get 4 spaces instead, and when you hit the backspace it removes 4 spaces (geany does this). Whatever you use, I suggest turning on the display of whitespace in your editor. It will then show tabs as "--->" and spaces as a dot. Change the color in the highlighting preferences to be very subtle so it does not overwhelm the code. It will help you keep every file you work on consistent and such errors a thing of the past.
  • codegeek 14y ago
    Well explained. I get it now. Thanks
  • Rust 14y ago
    In your example, if both developers are using TABs instead of spaces, why would it matter that one sees it as 5 spaces and the other as 8? It's still just a single TAB character either way. Plus, each developer has the freedom to choose how many spaces a TAB is - I like 8 when I'm using my big monitor, but I prefer 4 on my laptop. With TABs, I can see it both ways depending on the machine. On the off chance that I'm ever actually editing in a smaller window, I can even set it to 2 characters instead, but when I open that file again on another machine, I can see it as 4 or 8 characters.
    • cutie 14y ago
      Yes, there's an error there, conflating two ideas. I think tabs-only can still cause a problem, say when lining up comments on the end of a line because there might be a different amount needed per line depending on its length. Still, you can't be sure what other people will have, so for interop spaces it is. It might not be the case for everyone, but my laptop screen is 1920x1080 and has more room for text than I can use. In a three way merge your strategy could help me perhaps.