Re: Writing to stdout and a log file
Mike wrote: I would like my 'print' statements to send its output to the user's screen and a log file. This is my initial attempt: class StdoutLog(file): def __init__(self, stdout, name='/tmp/stdout.log', mode='w',bufsize=-1): super(StdoutLog, self).__init__(name,mode,bufsize) self.stdout = stdout def write(self, data): self.stdout.write(data) What happens when you do a self.stdout.flush() here? self.write(data) import sys sys.stdout = StdoutLog(sys.stdout) print 'STDOUT', sys.stdout When the program is run the string is written to the log file but nothing appears on my screen. Where's the screen output? It looks like the superclass's write() method is getting called instead of the StdoutLog instance's write() method. The python documentation says 'print' should write to sys.stdout.write() but that doesn't seem to be happening. Any idea what's going one? Or ideas on how to debug this? Thanks, Mike I had the same problem (writing to file and stdout with print) and my solution was *not* to subclass file and instead add a self.outfile=file(...) to the constructor. HTH, Wolfram -- http://mail.python.org/mailman/listinfo/python-list
Re: Writing to stdout and a log file
flushing stdout has no effect. I've got an implementation that does not subclass file. It's not as nice but it works. -- http://mail.python.org/mailman/listinfo/python-list
Re: Writing to stdout and a log file
Mike wrote: I should've mentioned I want StdoutLog to subclass the 'file' type because I need all the file attributes available. You might use a surrogate pattern. Here's one I use for this kind of situation, where I want to subclass but that can't be done for some reason. class SurrogateNotInitedError(exceptions.AttributeError): pass class Surrogate(object): def __init__(self, data): self._data = data def __getattr__(self, name): if name == _data: raise SurrogateNotInitedError, name else: try: return getattr(self._data, name) except SurrogateNotInitedError: raise SurrogateNotInitedError, name I'll leave it as an exercise to the reader to make this work when self._data is actually a list of objects instead of a single object. You'll obviously need special logic for different methods, like write(), since for some of them you will want to call every object in self._data, and others only a single object. -- Michael Hoffman -- http://mail.python.org/mailman/listinfo/python-list
Re: Writing to stdout and a log file
Perfect. This is what Ill use. Thanks! Mike -- http://mail.python.org/mailman/listinfo/python-list
Re: Writing to stdout and a log file
This variation works: # class Tee: def __init__(self, *args): self.files = args def write(self, data): for f in self.files: result = f.write(data) return result def writelines(self, seq): for i in seq: self.write(i) import sys sys.stdout = Tee(sys.stdout, open(/tmp/stdout.log, w)) print 'STDOUT', sys.stdout # It appears that the 'print' statement always uses file.write if isinstance(sys.stdout, file). I don't know whether this has been reported as a bug before, or if there's a reason for the current behavior. It may be an accidental behavior that is left over from the days when builtin types were not subclassable. Jeff pgp7JrGs05dLk.pgp Description: PGP signature -- http://mail.python.org/mailman/listinfo/python-list
Re: Writing to stdout and a log file
Thanks. I should've mentioned I want StdoutLog to subclass the 'file' type because I need all the file attributes available. I could add all the standard file methods and attributes to StdoutLog without subclassing 'file' but I'd rather avoid this if I can. -- http://mail.python.org/mailman/listinfo/python-list
Re: Writing to stdout and a log file
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.c7 Nov 2004 14:15:28 - 2.193 +++ Objects/fileobject.c20 Apr 2005 02:41:32 - @@ -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(); pgpnLHNwKqjp4.pgp Description: PGP signature -- http://mail.python.org/mailman/listinfo/python-list