Why does PEP-8 specify a maximum line length of 79 characters

Question

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

User · Answer

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

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

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