Objects/fileobject.c (part 2)

Source:

cpython 3.14 @ ab2d84fe1023/Objects/fileobject.c ↗

This annotation covers the write helpers used by print() and the standard stream setup. See objects_fileobject_detail for open(), FileIO.__init__, and BufferedWriter.

Map

Lines	Symbol	Role
1-80	PyFile_WriteObject	Write repr(obj) or str(obj) to a file-like object
81-160	PyFile_WriteString	Write a C string to a file-like object
161-260	sys.stdin / stdout / stderr setup	Wrap OS file descriptors in TextIOWrapper
261-400	_Py_SetStandardStreamEncoding	Override encoding before initialization

Reading

PyFile_WriteObject

// CPython: Objects/fileobject.c:48 PyFile_WriteObject
int
PyFile_WriteObject(PyObject *v, PyObject *f, int flags)
{
    /* flags: Py_PRINT_RAW = use str(); otherwise use repr() */
    if (f == NULL || f == Py_None) {
        PyErr_SetString(PyExc_TypeError,
                        "writeobject with NULL file");
        return -1;
    }
    PyObject *writer = PyObject_GetAttr(f, &_Py_ID(write));
    if (writer == NULL) return -1;
    PyObject *value;
    if (flags & Py_PRINT_RAW)
        value = PyObject_Str(v);
    else
        value = PyObject_Repr(v);
    if (value == NULL) { Py_DECREF(writer); return -1; }
    PyObject *result = PyObject_CallOneArg(writer, value);
    Py_DECREF(writer);
    Py_DECREF(value);
    if (result == NULL) return -1;
    Py_DECREF(result);
    return 0;
}

print(obj, file=f) calls PyFile_WriteObject(obj, f, Py_PRINT_RAW) which calls str(obj), then f.write(str_obj). The Py_PRINT_RAW flag distinguishes print (str) from repr() display.

PyFile_WriteString

// CPython: Objects/fileobject.c:80 PyFile_WriteString
int
PyFile_WriteString(const char *s, PyObject *f)
{
    /* Write a NUL-terminated C string to f.
       Used for tracebacks, prompts, and error messages. */
    if (f == NULL) {
        /* Fallback: write to stderr via C stdio */
        fputs(s, stderr);
        return 0;
    }
    PyObject *v = PyUnicode_FromString(s);
    if (v == NULL) return -1;
    int result = PyFile_WriteObject(v, f, Py_PRINT_RAW);
    Py_DECREF(v);
    return result;
}

sys.stdin/stdout/stderr setup

// CPython: Objects/fileobject.c:200 _PySys_SetAttr
/* Standard streams are set up in Py_InitializeMain:
   sys.stdin  = TextIOWrapper(FileIO(0, 'r'), encoding, errors='replace')
   sys.stdout = TextIOWrapper(FileIO(1, 'w'), encoding, line_buffering=True)
   sys.stderr = TextIOWrapper(FileIO(2, 'w'), encoding, errors='backslashreplace')
   The encoding is determined by locale or UTF-8 mode.
*/

sys.stdout is line-buffered by default (flushes on \n). sys.stderr uses errors='backslashreplace' to prevent UnicodeEncodeError from masking the original error.

_Py_SetStandardStreamEncoding

// CPython: Objects/fileobject.c:320 _Py_SetStandardStreamEncoding
int
_Py_SetStandardStreamEncoding(const char *encoding, const char *errors)
{
    /* Called before Py_Initialize() to override the default encoding.
       Used by: PYTHONIOENCODING env variable, -X utf8, UTF-8 mode. */
    if (_Py_StandardStreamEncoding == NULL) {
        _Py_StandardStreamEncoding = strdup(encoding);
    }
    if (_Py_StandardStreamErrors == NULL) {
        _Py_StandardStreamErrors = strdup(errors);
    }
    return 0;
}

PYTHONIOENCODING=utf-8:replace sets the encoding to UTF-8 with errors='replace' for all three standard streams.

gopy notes

PyFile_WriteObject is objects.FileWriteObject in objects/fileobject.go. Standard stream setup is in pythonrun/init.go which wraps os.Stdin/Stdout/Stderr as objects.TextIOWrapper. _Py_SetStandardStreamEncoding is respected via the PYTHONIOENCODING environment variable check in pythonrun.SetupStandardStreams.