Quoting long strings without newlines in Python

I am trying to write a long string in Python that gets displayed as the help item of an OptParser option. In my source c开发者_StackOverflow中文版ode .py file, I'd like to place newlines so that my code doesn't spend new lines. However, I don't want those newlines to affect how that string is displayed when the code is run. For example, I want to write:

   parser.add_option("--my-option", dest="my_option", nargs=2, default=None,
              help='''Here is a long description of my option.  It does many things
              but I want the shell to decide how to display this explanation. However,
              I want newlines in this string.''')

the above way of doing things will make it so when I call my program with --help, the explanation of my-option will have many gaps in it.

How can I fix this?

thanks.

---

You can concatenate string literals just like in C, so "foo" "bar" is the same as "foobar", meaning this should do what you want:

parser.add_option("--my-option", dest="my_option", nargs=2, default=None, 
          help="Here is a long description of my option.  It does many things "
          "but I want the shell to decide how to display this explanation. However, "
          "I want newlines in this string.") 

Note that you don't need backslash line continuation characters because the whole thing is within parentheses.

---

Just take advantage of string-literal juxtaposition -- in Python, like in C, if two string literals are next to each other with just whitespace in-between (including newlines), the compiler will merge them into a single string literal, ignoring the whitespace. I.e.:

parser.add_option("--my-option", dest="my_option", nargs=2, default=None,
                  help='Here is a long description of my option.  It does '
                       'many things but I want the shell to decide how to '
                       'display this explanation. However, I do NOT want '
                       'newlines in this string.')

I'm assuming that by "I want" you actually mean "I do NOT want" here;-).

Note the trailing spaces at the end of each piece of the literal you're passing as help: you have to put them there explicitly, or else the juxtaposition would make "words" such as doesmany and so on;-).

Note that, very differently from what some answers and comments claim, you most definitely don't need ugly, redundant pluses and-or backslashes here -- no pluses needed because the compiler applies juxtaposition for you, no backslashes needed either because this set of physical lines is a single logical line (thanks to the open paren not being closed yet until the end of the set of physical lines!).

---

Default help formatter reformats the string so you can use newlines in the help string as you like:

>>> from optparse import OptionParser
>>> parser = OptionParser()
>>> parser.add_option('--my-option', help='''aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
aaaaaaaaaaaaaaaaaaaaaaa
... b
... c                            d
... e
... f''')
>>> parser.print_help()
Usage: bpython [options]

Options:
  -h, --help            show this help message and exit
  --my-option=MY_OPTION
                        aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
                        aaa b c                            d e f

To remove any common leading space you could use textwrap.dedent:

>>> from optparse import OptionParser
>>> from textwrap import dedent
>>> parser = OptionParser()
>>> parser.add_option('--my-option', help=dedent('''\
...     Here is a long description of my option.  It does many things
...     but I want the shell to decide how to display this
...     explanation. However, I want newlines in this string.'''))
>>> parser.print_help()
Usage:  [options]

Options:
  -h, --help            show this help message and exit
  --my-option=MY_OPTION
                        Here is a long description of my option.  It does many
                        things but I want the shell to decide how to display
                        this explanation. However, I want newlines in this
                        string.

---

This works:

foo = "abc" + \
    "def" + \
    "ghi"

print foo