How to write very long string that conforms with PEP8 and prevent E501

Question

Since neighboring string constants are automatically concatenated, you can code it like this:

s = ("this is my really, really, really, really, really, really, "  
     "really long string that I'd like to shorten.")

Note no plus sign, and I added the extra comma and space that follows the formatting of your example.

Personally I don't like the backslashes, and I recall reading somewhere that its use is actually deprecated in favor of this form which is more explicit. Remember "Explicit is better than implicit."

I consider the backslash to be less clear and less useful because this is actually escaping the newline character. It's not possible to put a line end comment after it if one should be necessary. It is possible to do this with concatenated string constants:

s = ("this is my really, really, really, really, really, really, " # comments ok
     "really long string that I'd like to shorten.")

---

I used a Google search of "python line length" which returns the PEP8 link as the first result, but also links to another good StackOverflow post on this topic: "Why should Python PEP-8 specify a maximum line length of 79 characters?"

Another good search phrase would be "python line continuation".

Implicit concatenation might be the cleanest solution:

s = "this is my really, really, really, really, really, really," \
    " really long string that I'd like to shorten."

Edit On reflection I agree that Todd's suggestion to use brackets rather than line continuation is better for all the reasons he gives. The only hesitation I have is that it's relatively easy to confuse bracketed strings with tuples.

I think the most important word in your question was "suggests".

Coding standards are funny things. Often the guidance they provide has a really good basis when it was written (e.g. most terminals being unable to show > 80 characters on a line), but over time they become functionally obsolete, but still rigidly adhered to. I guess what you need to do here is weigh up the relative merits of "breaking" that particular suggestion against the readability and mainatinability of your code.

Sorry this doesn't directly answer your question.

You lost a space, and you probably need a line continuation character, ie. a \.

s = "this is my really, really, really, really, really, really" +  \
    " really long string that I'd like to shorten."

or even:

s = "this is my really, really, really, really, really, really"  \
    " really long string that I'd like to shorten."

Parens would also work instead of the line continuation, but you risk someone thinking you intended to have a tuple and had just forgotten a comma. Take for instance:

s = ("this is my really, really, really, really, really, really"
    " really long string that I'd like to shorten.")

versus:

s = ("this is my really, really, really, really, really, really",
    " really long string that I'd like to shorten.")

With Python's dynamic typing, the code may run either way, but produce incorrect results with the one you didn't intend.

Backslash:

s = "this is my really, really, really, really, really, really" +  \
    "really long string that I'd like to shorten."

or wrap in parens:

s = ("this is my really, really, really, really, really, really" + 
    "really long string that I'd like to shorten.")

If you must insert a long string literal and want flake8 to shut up, you can use it's shutting up directives. For example, in a testing routine I defined some fake CSV input. I found that splitting it over more lines that it had rows would be mightily confusing, so I decided to add a # noqa: E501 as follows:

csv_test_content = """"STATION","DATE","SOURCE","LATITUDE","LONGITUDE","ELEVATION","NAME","REPORT_TYPE","CALL_SIGN","QUALITY_CONTROL","WND","CIG","VIS","TMP","DEW","SLP","AA1","AA2","AY1","AY2","GF1","MW1","REM"
"94733099999","2019-01-03T22:00:00","4","-32.5833333","151.1666666","45.0","SINGLETON STP, AS","FM-12","99999","V020","050,1,N,0010,1","22000,1,9,N","025000,1,9,9","+0260,1","+0210,1","99999,9","24,0000,9,1",,"0,1,02,1","0,1,02,1","01,99,1,99,9,99,9,99999,9,99,9,99,9","01,1","SYN05294733 11/75 10502 10260 20210 60004 70100 333 70000="
"94733099999","2019-01-04T04:00:00","4","-32.5833333","151.1666666","45.0","SINGLETON STP, AS","FM-12","99999","V020","090,1,N,0021,1","22000,1,9,N","025000,1,9,9","+0378,1","+0172,1","99999,9","06,0000,9,1",,"0,1,02,1","0,1,02,1","03,99,1,99,9,99,9,99999,9,99,9,99,9","03,1","SYN04294733 11/75 30904 10378 20172 60001 70300="
"94733099999","2019-01-04T22:00:00","4","-32.5833333","151.1666666","45.0","SINGLETON STP, AS","FM-12","99999","V020","290,1,N,0057,1","99999,9,9,N","020000,1,9,9","+0339,1","+0201,1","99999,9","24,0000,9,1",,"0,1,02,1","0,1,02,1",,"02,1","SYN05294733 11970 02911 10339 20201 60004 70200 333 70000="
"94733099999","2019-01-05T22:00:00","4","-32.5833333","151.1666666","45.0","SINGLETON STP, AS","FM-12","99999","V020","200,1,N,0026,1","99999,9,9,N","000100,1,9,9","+0209,1","+0193,1","99999,9","24,0004,3,1",,"1,1,02,1","1,1,02,1","08,99,1,99,9,99,9,99999,9,99,9,99,9","51,1","SYN05294733 11/01 82005 10209 20193 69944 75111 333 70004="
"94733099999","2019-01-08T04:00:00","4","-32.5833333","151.1666666","45.0","SINGLETON STP, AS","FM-12","99999","V020","070,1,N,0026,1","22000,1,9,N","025000,1,9,9","+0344,1","+0213,1","99999,9","06,0000,9,1",,"2,1,02,1","2,1,02,1","04,99,1,99,9,99,9,99999,9,99,9,99,9","02,1","SYN04294733 11/75 40705 10344 20213 60001 70222="
"""  # noqa: E501