#2630: Implement PEP 3138.

The repr() of a string now contains printable Unicode characters unescaped.
The new ascii() builtin can be used to get a repr() with only ASCII characters in it.

PEP and patch were written by Atsuo Ishimoto.

Doc/c-api/unicode.rst

@@ -144,6 +144,18 @@ the Python configuration.
 
    Return 1 or 0 depending on whether *ch* is an alphanumeric character.
 
+
+.. cfunction:: int Py_UNICODE_ISPRINTABLE(Py_UNICODE ch)
+
+   Return 1 or 0 depending on whether *ch* is a printable character.
+   Nonprintable characters are those characters defined in the Unicode character
+   database as "Other" or "Separator", excepting the ASCII space (0x20) which is
+   considered printable.  (Note that printable characters in this context are
+   those which should not be escaped when :func:`repr` is invoked on a string.
+   It has no bearing on the handling of strings written to :data:`sys.stdout` or
+   :data:`sys.stderr`.)
+
+
 These APIs can be used for fast direct character conversions:
 
 
@@ -266,6 +278,9 @@ APIs:
    |                   |                     | of what the platform's         |
    |                   |                     | ``printf`` yields.             |
    +-------------------+---------------------+--------------------------------+
+   | :attr:`%A`        | PyObject\*          | The result of calling          |
+   |                   |                     | :func:`ascii`.                 |
+   +-------------------+---------------------+--------------------------------+
    | :attr:`%U`        | PyObject\*          | A unicode object.              |
    +-------------------+---------------------+--------------------------------+
    | :attr:`%V`        | PyObject\*, char \* | A unicode object (which may be |