[Python-ideas] Dart like multi line strings identation

[Terry Reedy]

On 3/31/2018 10:50 AM, Marius Räsener wrote:

> What I have in mind is probably best described with an Example:
> 
> print("""
>      I am a
>      multiline
>      String.
>      """)
> 
> the closing quote defines the "margin indentation" - so in this example 
> all lines would get reduces by their leading 4 spaces, resulting in a 
> "clean" and unintended string.

Adding additional default processing to multiline strings is not 
possible within back-compatibility constraints.  It is also not 
necessary.  The current

print("I am a\n"
       "multiline\n"
       "String.\n")

does exactly the same thing as the proposal 2 fewer lines and is more 
flexible, as one can add an initial \n or an extra \n in the middle or 
omit the final \n.

(For the example, print("I am a\nmultiline\nString\n", also works in 1 
line, but does not represent the general case of multiples lone lines.)
---

In 3.6, we introduced a new prefix, 'f', so there was no back 
compatibility issue.  There was, however, a combinatorial explosion 
issue, as 'F' was also added (a mistake, I now think), and no order 
requirement (possibly another mistake).  Hence

stringprefix    ::=  "r" | "u" | "R" | "U"

grew to

stringprefix    ::=  "r" | "u" | "R" | "U" | "f" | "F"
                      | "fr" | "Fr" | "fR" | "FR" | "rf" | "rF" | "Rf" | 
"RF"

New unordered 'd' and 'D' prefixes, for 'dedent', applied to multiline 
strings only, would multiply the number of alternatives by about 5 and 
would require another rewrite of all code (Python or not) that parses 
Python code (such as in syntax colorizers).

-- 
Terry Jan Reedy