[Python-Dev] Re: PEP 295 - Interpretation of multiline string constants

[Michael Chermside]

Stephan Koltsov writes:
 > I wrote a PEP, its number is 295, it is in attachment.
       [... PEP on stripping newline and preceeding spaces
            multi-line string literals ...]

I see ___ motivations for the proposals in this PEP, and propose 
alternative solutions for each. NONE of my alternative solutions 
requires ANY modification to the Python language.

--------

Motivation 1 -- Lining up line 1 of multi-line quotes:

Senario: - Use of string with things "lined up" neatly

     >>> def someFunction():
     ...     aMultiLineString = """Foo  X   1.0
     ... Bar  Y   2.5
     ... Baz  Z  15.0
     ... Spam Q  38.9
     ... """

     Notice how line 1 doesn't line up neatly with lines 2-4 because of
     the indenting as well as the text assigning it to a variable. This
     is annoying, and makes it awkward to read.

Solution: - Use a backslash to escape an initial newline

     >>> def someFunction():
     ...     aMultiLineString = """\
     ... Foo  X   1.0
     ... Bar  Y   2.5
     ... Baz  Z  15.0
     ... Spam Q  38.9
     ... """

     Notice that now everything lines up neatly. And we don't need to
     modify Python at all for this to work.

--------

Motivation 2 - Maintaining Indentation

Senario: - Outdenting misleads the eye

     >>> class SomeClass:
     ...     def visitFromWaiter(self):
     ...         if self.seated:
     ...             self.silverware = ['fork','spoon']
     ...             self.menu = """Spam
     ... Spam and Eggs
     ... Spam on Rye
     ... """
     ...             self.napkin = DirtyNapkin()

     Notice how the indentation makes it quite clear when we are inside a
     class, a method, or a flow-control statement by merely watching the
     left-hand margin. But this is crudely interrupted by the multi-line
     string.

Solution: - Process the multi-line string through a function

     >>> class SomeClass:
     ...     def visitFromWaiter(self):
     ...         if self.seated:
     ...             self.silverware = ['fork','spoon']
     ...             self.menu = stripIndent( """\
     ...                 Spam
     ...                 Spam and Eggs
     ...                 Spam on Rye
     ...                 """ )
     ...             self.napkin = DirtyNapkin()

     where stripIndent() has been defined as:

     >>> def stripIndent( s ):
     ...     indent = len(s) - len(s.lstrip())
     ...     sLines = s.split('\n')
     ...     resultLines = [ line[indent:] for line in sLines ]
     ...     return ''.join( resultLines )

     Notice how it is now NICELY indented, at the expense of a tiny
     little 4-line function. Of course, there are faster and safer
     ways to write stripIndent() (I, personally, would use a version
     that checked that each line started with identical indentation
     and raised an exception otherwise), but this version illustrates
     the idea while being very, very readable.

----

In conclusion, I propose you use simpler methods available WITHIN the 
language for solving this problem, rather than proposing a PEP to modify 
the language itself.

-- Michael Chermside