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SF patch #907403: Improvements to cStringIO.writelines()

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The writelines() method now accepts any iterable argument and writes
the lines one at a time rather than using ''.join(lines) followed by
a single write.  Results in considerable memory savings and makes
the method suitable for use with generator expressions.
This commit is contained in:
Raymond Hettinger 2004-03-08 18:17:31 +00:00
parent 73360a3e61
commit 6ec099658a
2 changed files with 29 additions and 32 deletions
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6
Lib/StringIO.py
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@ -178,8 +178,10 @@ class StringIO:
self.len = newpos self.len = newpos
self.pos = newpos self.pos = newpos
def writelines(self, list): def writelines(self, iterable):
self.write(''.join(list)) write = self.write
for line in iterable:
write(line)
def flush(self): def flush(self):
_complain_ifclosed(self.closed) _complain_ifclosed(self.closed)

55
Modules/cStringIO.c
View file

@ -416,40 +416,35 @@ O_close(Oobject *self, PyObject *unused) {
return Py_None; return Py_None;
} }
PyDoc_STRVAR(O_writelines__doc__, PyDoc_STRVAR(O_writelines__doc__,
"writelines(sequence_of_strings): write each string"); "writelines(sequence_of_strings) -> None. Write the strings to the file.\n"
"\n"
"Note that newlines are not added. The sequence can be any iterable object\n"
"producing strings. This is equivalent to calling write() for each string.");
static PyObject * static PyObject *
O_writelines(Oobject *self, PyObject *args) { O_writelines(Oobject *self, PyObject *args) {
PyObject *tmp = 0; PyObject *it, *s;
static PyObject *joiner = NULL;
it = PyObject_GetIter(args);
if (!joiner) { if (it == NULL)
PyObject *empty_string = PyString_FromString("");
if (empty_string == NULL)
return NULL;
joiner = PyObject_GetAttrString(empty_string, "join");
Py_DECREF(empty_string);
if (joiner == NULL)
return NULL;
}
if (PyObject_Size(args) < 0) return NULL;
args = PyTuple_Pack(1, args);
if (args == NULL)
return NULL; return NULL;
tmp = PyObject_Call(joiner, args, NULL); while ((s = PyIter_Next(it)) != NULL) {
Py_DECREF(args); int n;
UNLESS (tmp) return NULL; char *c;
if (PyString_AsStringAndSize(s, &c, &n) == -1) {
args = PyTuple_Pack(1, tmp); Py_DECREF(it);
Py_DECREF(tmp); Py_DECREF(s);
UNLESS (args) return NULL; return NULL;
}
tmp = O_write(self, args); if (O_cwrite((PyObject *)self, c, n) == -1) {
Py_DECREF(args); Py_DECREF(it);
return tmp; Py_DECREF(s);
return NULL;
}
Py_DECREF(s);
}
Py_DECREF(it);
Py_RETURN_NONE;
} }
static struct PyMethodDef O_methods[] = { static struct PyMethodDef O_methods[] = {