Writing to stdout and a log file

[Jeff Epler]

In that case, it looks like you won't be able to get what you want
without modifying CPython.  PRINT_ITEM calls PyFile_SoftSpace,
PyFile_WriteString, and PyFile_WriteObject, which all use
PyFile_Check().  It might be as simple as changing these to
PyFile_CheckExact() calls in PyFile_WriteString / PyFile_WriteObject,
but I have no idea whether the test suite still works after this change
is made.  It does make this program work (it prints things from X.write):

class X(file):
    def write(self, s):
        print "X.write", `s`
        return file.write(self, s)

import sys
x = X("/tmp/out.txt", "w")
print >>x, 42

I don't care to be the champion of this patch, or to submit it to
sourceforge; I suspect there should be a better review of PyFile_Check
vs PyFile_CheckExact uses in fileobject.c, instead of just picking the
few spots that make this usage work.  Before being submitted as a patch,
a testcase should be added too.  Feel free to run with this if you feel
strongly about it.

Jeff

Index: Objects/fileobject.c
===================================================================
RCS file: /cvsroot/python/python/dist/src/Objects/fileobject.c,v
retrieving revision 2.193
diff -u -u -r2.193 fileobject.c
--- Objects/fileobject.c	7 Nov 2004 14:15:28 -0000	2.193
+++ Objects/fileobject.c	20 Apr 2005 02:41:32 -0000
@@ -2012,7 +2012,7 @@
 		PyErr_SetString(PyExc_TypeError, "writeobject with NULL file");
 		return -1;
 	}
-	else if (PyFile_Check(f)) {
+	else if (PyFile_CheckExact(f)) {
 		FILE *fp = PyFile_AsFile(f);
 #ifdef Py_USING_UNICODE
 		PyObject *enc = ((PyFileObject*)f)->f_encoding;
@@ -2082,7 +2082,7 @@
 					"null file for PyFile_WriteString");
 		return -1;
 	}
-	else if (PyFile_Check(f)) {
+	else if (PyFile_CheckExact(f)) {
 		FILE *fp = PyFile_AsFile(f);
 		if (fp == NULL) {
 			err_closed();

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