[Python-Dev] Strings: '\012' -> '\n'

Ka-Ping Yee ping@lfw.org
Thu, 18 Jan 2001 01:29:13 -0800 (PST)

On Tue, 16 Jan 2001, Guido van Rossum wrote:
> You mean the tp_print and tp_str function slots in type objects,
> right?  tp_print *should* always render exactly the same as tp_str.
> tp_print is used by the print statement, not by value display at the
> interactive prompt.

Uh, i hate to disagree with you about your own interpreter, but:

    com_expr_stmt in Python/compile.c
        inserts a PRINT_EXPR opcode if c_interactive is true;
    eval_code2 in Python/ceval.c
        handles PRINT_EXPR by calling displayhook;
    sys_displayhook in Python/sysmodule.c
        prints the object by calling PyFile_WriteObject on sys.stdout;
    PyFile_WriteObject in Objects/fileobject.c
        calls PyObject_Print if the file is really a PyFileObject;
    PyObject_Print in Objects/object.c
        calls op->ob_type->tp_print if it's not NULL.

The print statement produces a PRINT_ITEM opcode, which invokes
PyFile_WriteObject with a Py_PRINT_RAW flag.  That Py_PRINT_RAW
flag is propagated down to PyObject_Print and into string_print,
where it causes the string to fwrite itself directly without quoting.

> So, string_print most definitely should *not* be changed -- only
> string_repr!

I had to change them both before i actually saw the change in the
interactive interpreter.  Actually, your statement above (that the
two should always render the same) seems to imply that if i change
one, i must also change the other.

-- ?!ng