Pythonic way to create a long multi-line string

Question

I have a very long query  I would like to split it in several lines in Python  A way to do it in JavaScript would be using several sentences and joining them with a   operator  I know  maybe it s not the most efficient way to do it  but I m not really concerned about performance in this stage  just code readability   Example   var long string    some text not important  just garbage to                       illustrate my example     I tried doing something similar in Python  but it didn t work  so I used   to split the long string  However  I m not sure if this is the only best pythonicest way of doing it  It looks awkward   Actual code   query    SELECT action descr as  action           role id as role id         role descr as role        FROM         public role action def         public role         public record def          public action        WHERE role id   role action def role id AND        record def id   role action def def id AND        action id   role action def action id AND        role action def account id       account id     AND        record def account id     account id     AND        def id     def id

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If you don t want a multiline string  but just have a long single line string  you can use parentheses  Just make sure you don t include commas between the string segments  then it will be a tuple   query     SELECT   action descr as  quot action quot               role id as role id             role descr as role             FROM             public role action def             public role             public record def              public action             WHERE role id   role action def role id AND             record def id   role action def def id AND             action id   role action def action id AND             role action def account id     account id   AND             record def account id   account id   AND             def id   def id   In a SQL statement like what you re constructing  multiline strings would also be fine  But if the extra white space a multiline string would contain would be a problem  then this would be a good way to achieve what you want

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I use a recursive function to build complex SQL queries  This technique can generally be used to build large strings while maintaining code readability    Utility function to recursively resolve SQL statements    CAUTION  Use this function carefully  Pass correct SQL parameters       TODO  This should never happen but check for infinite loops def resolveSQL sql seed  sqlparams       sql   sql seed    sqlparams      if sql    sql seed          return     join  x strip   for x in sql split         else          return resolveSQL sql  sqlparams   P S   Have a look at the awesome python-sqlparse library to pretty print SQL queries if needed

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tl dr  Use  quot  quot  quot   and  quot  quot  quot  to wrap the string  as in string    quot  quot  quot   This is a long string spanning multiple lines   quot  quot  quot   From the official Python documentation   String literals can span multiple lines  One way is using triple-quotes   quot  quot  quot     quot  quot  quot  or            End of lines are automatically included in the string  but it   s possible to prevent this by adding a   at the end of the line  The following example   print  quot  quot  quot   Usage  thingy  OPTIONS       -h                        Display this usage message      -H hostname               Hostname to connect to  quot  quot  quot     produces the following output  note that the initial newline is not included    Usage  thingy  OPTIONS       -h                        Display this usage message      -H hostname               Hostname to connect to

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For defining a long string inside a dict  keeping the newlines but omitting the spaces  I ended up defining the string in a constant like this   LONG STRING         This is a long sting that contains newlines  The newlines are important       my dict         foo    bar       string   LONG STRING

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Your actual code shouldn t work  you are missing white spaces at the end of  quot lines quot   for example  role descr as roleFROM      There are triple quotes for multiline strings  string    quot  quot  quot line   line2   line3 quot  quot  quot   It will contain the line breaks and extra spaces  but for SQL that s not a problem

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In Python    3 6 you can use Formatted string literals  f string   query  f   SELECT   action descr as  action      role id as role id      role descr as role     FROM     public role action def      public role      public record def      public action     WHERE role id   role action def role id AND     record def id   role action def def id AND     action id   role action def action id AND     role action def account id    account id  AND     record def account id    account id  AND     def id    def id

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Another option that I think is more readable when the code  e g   a variable  is indented and the output string should be a one-liner  no newlines   def some method         long string    quot  quot  quot  A presumptuous long string which looks a bit nicer in a text editor when written over multiple lines  quot  quot  quot  strip   n   replace   n             return long string

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As a general approach to long strings in Python  you can use triple quotes  split and join   str       join    Lorem ipsum dolor sit amet  consectetur adipiscing         elit  sed do eiusmod tempor incididunt ut labore et dolore         magna aliqua  Ut enim ad minim veniam  quis nostrud exercitation         ullamco laboris nisi ut aliquip ex ea commodo     split     Output   Lorem ipsum dolor sit amet  consectetur adipiscing elit  sed do eiusmod tempor incididunt ut labore et dolore magna aliqua  Ut enim ad minim veniam  quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo    With regard to OP s question relating to a SQL query  the answer below disregards the correctness of this approach to building SQL queries and focuses only on building long strings in a readable and aesthetic way without additional imports  It also disregards the computational load this entails  Using triple quotes  we build a long and readable string which we then break up into a list using split   thereby stripping the white space and then join it back together with     join    Finally we insert the variables using the format   command  account id   123 def id   321   str           SELECT action descr AS  quot action quot   role id AS role id  role descr AS role     FROM public role action def  public role  public record def  public action     WHERE role id   role action def role id     AND record def id   role action def def id     AND  action id   role action def action id     AND role action def account id          AND record def account id          AND def id               query       join  str split    format account id  account id  def id    Produces  SELECT action descr AS  quot action quot   role id AS role id  role descr AS role FROM public role action def  public role  public record def  public action WHERE role id   role action def role id AND record def id   role action def def id AND action id   role action def action id AND role action def account id   123 AND record def account id 123 AND def id 321  This approach is not in line with PEP 8  but I find it useful at times  Please note that the curly brackets in the original string are used by the format   function

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Generally  I use list and join for multi-line comments string  lines   list   lines append  SELECT action enter code here descr as  quot action quot      lines append  role id as role id    lines append  role descr as role   lines append  FROM    lines append  public role action def    lines append  public role    lines append  public record def     lines append  public action   query    quot   quot  join lines   You can use any string to join all these list elements  like   n  newline  or     comma  or     space

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From the official Python documentation   String literals can span multiple lines  One way is using triple-quotes   quot  quot  quot     quot  quot  quot  or            End of lines are automatically included in the string  but it   s possible to prevent this by adding a   at the end of the line  The following example   print  quot  quot  quot   Usage  thingy  OPTIONS       -h                        Display this usage message      -H hostname               Hostname to connect to  quot  quot  quot     produces the following output  note that the initial newline is not included

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Others have mentioned the parentheses method already  but I d like to add that with parentheses  inline comments are allowed   Comment on each fragment   nursery rhyme          Mary had a little lamb              Comments are great       its fleece was white as snow        And everywhere that Mary went        her sheep would surely go           What a pesky sheep      Comment not allowed after continuation   When using backslash line continuations       comments are not allowed  You ll receive a SyntaxError  unexpected character after line continuation character error   nursery rhyme    Mary had a little lamb        These comments      its fleece was white as snow              are invalid       And everywhere that Mary went               her sheep would surely go       gt  SyntaxError  unexpected character after line continuation character   Better comments for Regex strings   Based on the example from https   docs python org 3 library re html re VERBOSE    a   re compile      r  d      the integral part     r         the decimal point     r  d      some fractional digits       Using VERBOSE flag  IDE usually can t syntax highight the string comment  a   re compile r    d      the integral part                            the decimal point                     d      some fractional digits     re X

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You can also include variables when using  quot  quot  quot  notation  foo    1234   long string    quot  quot  quot fosdl a sdlfklaskdf as as df ajsdfj asdfa sld a sdf alsdfl alsdfl  quot  quot  quot     foo    quot  quot  quot  aks asdkfkasdk fak quot  quot  quot   A better way is  with named parameters and  format    body    quot  quot  quot   lt html gt   lt head gt   lt  head gt   lt body gt       lt p gt Lorem ipsum  lt  p gt       lt dl gt           lt dt gt Asdf  lt  dt gt       lt dd gt  lt a href  quot  link  quot  gt  name  lt  a gt  lt  dd gt       lt  dl gt       lt  body gt   lt  html gt   quot  quot  quot  format      link  http   www asdf com       name  Asdf      print body

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Combining the ideas from  Levon or Jesse  Faheel and ddrscott with my formatting suggestion  you could write your query as  query     SELECT                 action descr as  quot action quot                  role id as role id                 role descr as role             FROM                 public role action def                 public role                 public record def                 public action             WHERE                 role id   role action def role id                 AND                 record def id   role action def def id                 AND                 action id   role action def action id                 AND                 role action def account id        account id                AND                 record def account id             account id                AND                 def id                            def id              vars    account id  account id  def id        A tuple of the query variables  cursor execute query  vars                    Using Python s sqlite3 module  Or like  vars      query     SELECT                 action descr as  quot action quot                  role id as role id                 role descr as role             FROM                 public role action def                 public role                 public record def                 public action             WHERE                 role id   role action def role id                 AND                 record def id   role action def def id                 AND                 action id   role action def action id                 AND                 role action def account id                      vars append account id  or                    AND                 record def account id                      vars append account id  or                    AND                 def id                      vars append def id  or                  cursor execute query  tuple vars      Using Python s sqlite3 module  Which could be interesting together with  IN  and  vars extend options  or n options len options     where  def n options count       return           join count             Or with the hint from darkfeline  that you might still make mistakes with those leading spaces and separators and also with named placeholders  SPACE SEP       COMMA SEP        AND SEP       AND    query   SPACE SEP join        SELECT           COMMA SEP join            action descr as  quot action quot             role id as role id            role descr as role                    FROM           COMMA SEP join            public role action def            public role            public record def            public action                    WHERE           AND SEP join            role id   role action def role id            record def id   role action def def id            action id   role action def action id            role action def account id    account id            record def account id    account id            def id    def id                       vars     account id  account id  def id  def id     A dictionary of the query variables cursor execute query  vars                          Using Python s sqlite3 module  See documentation of Cursor execute-function   quot This is the  most Pythonic  way  quot  -

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I find that when building long strings  you are usually doing something like building an SQL query  in which case this is best  query       join      Note double parentheses  join   takes an iterable      quot SELECT foo quot        quot FROM bar quot        quot WHERE baz quot       What Levon suggested is good  but it might be vulnerable to mistakes  query          quot SELECT foo quot       quot FROM bar quot       quot WHERE baz quot     query     quot SELECT fooFROM barWHERE baz quot     Probably not what you want

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I like this approach because it privileges reading  In cases where we have long strings there is no way  Depending on the level of indentation you are in and still limited to 80 characters per line    Well    No need to say anything else In my view  the Python style guides are still very vague  I took the Eero Aaltonen approach  because it privileges reading and common sense  I understand that style guides should help us and not make our lives a mess  class ClassName        def method name            if condition 0              if condition 1                  if condition 2                      some variable 0     quot  quot  quot  some js func call      undefined                 some attr 0    value 0            some attr 1    value 1            some attr 2     quot  quot  quot    some variable 1    quot  quot  quot              undefined      undefined      true    quot  quot  quot

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Try something like this  Like in this format it will return you a continuous line like you have successfully enquired about this property   quot message quot   f You have successfully inquired about              f  enquiring property title  Property owned by              f  enquiring property client

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For example  sql     quot select field1  field2  field3  field4  quot          quot from table  quot          quot where condition1     quot          quot and condition2    quot   format 1  2   Output   select field1  field2  field3  field4 from table          where condition1 1 and condition2 2   If the value of the condition should be a string  you can do it like this  sql     quot select field1  field2  field3  field4  quot          quot from table  quot          quot where condition1   0    quot          quot and condition2   1   quot   format  2016-10-12    2017-10-12    Output   quot select field1  field2  field3  field4 from table where          condition1  2016-10-12  and condition2  2017-10-12  quot

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Are you talking about multi-line strings  Easy  use triple quotes to start and end them   s       this is a very         long string if I had the         energy to type more and more          You can use single quotes too  3 of them of course at start and end  and treat the resulting string s just like any other string   NOTE  Just as with any string  anything between the starting and ending quotes becomes part of the string  so this example has a leading blank  as pointed out by  root45   This string will also contain both blanks and newlines   I e       this is a very n        long string if I had the n        energy to type more and more        Finally  one can also construct long lines in Python like this    s     this is a very         long string too         for sure               which will not include any extra blanks or newlines  this is a deliberate example showing what the effect of skipping blanks will result in     this is a verylong string toofor sure        No commas required  simply place the strings to be joined together into a pair of parenthesis and be sure to account for any needed blanks and newlines

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You can also place the SQL statement in a separate file  action sql  and load it in the  py file with  with open  action sql   as f     query   f read    So the SQL statements will be separated from the Python code  If there are parameters in the SQL statement which needs to be filled from Python  you can use string formatting  like  s or  field

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Breaking lines by   works for me   Here is an example   longStr    This is a very long string              that I wrote to help somebody              who had a question about              writing long strings in Python

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I find textwrap dedent the best for long strings as described here   def create snippet        code snippet   textwrap dedent              int main int argc  char  argv                  return 0                         do something code snippet

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I found myself happy with this one   string      This is a very long string  containing commas  that I split up for readability    replace   n

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I personally find the following to be the best  simple  safe and Pythonic  way to write raw SQL queries in Python  especially when using Python s sqlite3 module   query           SELECT         action descr as action          role id as role id          role descr as role     FROM         public role action def          public role          public record def          public action     WHERE         role id   role action def role id         AND record def id   role action def def id         AND action id   role action def action id         AND role action def account id             AND record def account id             AND def id         vars    account id  account id  def id      a tuple of query variables cursor execute query  vars      using Python s sqlite3 module   Pros   Neat and simple code  Pythonic   Safe from SQL injection Compatible with both Python 2 and Python 3  it s Pythonic after all  No string concatenation required No need to ensure that the right-most character of each line is a space   Cons   Since variables in the query are replaced by the   placeholder  it may become a little difficult to keep track of which   is to be substituted by which Python variable when there are lots of them in the query

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I usually use something like this   text           This string was typed to be a demo     on how could we write a multi-line     text in Python        If you want to remove annoying blank spaces in each line  you could do as follows   text     n  join line lstrip   for line in text splitlines

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quot    la quot  Scala way  but I think is the most Pythonic way as the OP demands   description    quot  quot  quot                The intention of this module is to provide a method to               pass meta information in markdown  header files for               using it in jinja  templates                              Also  to provide a method to use markdown files as jinja               templates  Maybe you prefer to see the code than               to install it  quot  quot  quot  replace   n               n    n   replace                        If you want final str without jump lines  just put  n at the start of the first argument of the second replace   replace   n                        Note  the white line between  quot    templates  quot  and  quot Also      quot  requires a white space after the

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This approach uses   almost no internal punctuation by using a triple quoted string strips away local indentation using the inspect module uses Python 3 6 formatted string interpolation   f   for the account id and def id variables   This way looks the most Pythonic to me  import inspect  query   inspect cleandoc f        SELECT action descr as  quot action quot       role id as role id      role descr as role     FROM     public role action def      public role      public record def      public action     WHERE role id   role action def role id AND     record def id   role action def def id AND     action id   role action def action id AND     role action def account id    account id  AND     record def account id  account id  AND     def id  def id

[python] Pythonic way to create a long multi-line string

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