[3.7] bpo-36523: Add docstring to io.IOBase.writelines (pythonGH-12683).

(cherry picked from commit ab86521)

Co-authored-by: Marcin Niemira <[email protected]>

Lib/_pyio.py

@@ -546,6 +546,11 @@ def readlines(self, hint=None):
         return lines
 
     def writelines(self, lines):
+        """Write a list of lines to the stream.
+
+        Line separators are not added, so it is usual for each of the lines
+        provided to have a line separator at the end.
+        """
         self._checkClosed()
         for line in lines:
             self.write(line)

Misc/NEWS.d/next/Documentation/2019-04-04-19-11-47.bpo-36523.sG1Tr4.rst

@@ -0,0 +1 @@
+Add docstring for io.IOBase.writelines().

Modules/_io/clinic/iobase.c.h

@@ -230,7 +230,11 @@ _io__IOBase_readlines(PyObject *self, PyObject *const *args, Py_ssize_t nargs)
 PyDoc_STRVAR(_io__IOBase_writelines__doc__,
 "writelines($self, lines, /)\n"
 "--\n"
-"\n");
+"\n"
+"Write a list of lines to stream.\n"
+"\n"
+"Line separators are not added, so it is usual for each of the\n"
+"lines provided to have a line separator at the end.");
 
 #define _IO__IOBASE_WRITELINES_METHODDEF    \
     {"writelines", (PyCFunction)_io__IOBase_writelines, METH_O, _io__IOBase_writelines__doc__},
@@ -279,4 +283,4 @@ _io__RawIOBase_readall(PyObject *self, PyObject *Py_UNUSED(ignored))
 {
     return _io__RawIOBase_readall_impl(self);
 }
-/*[clinic end generated code: output=64989ec3dbf44a7c input=a9049054013a1b77]*/
+/*[clinic end generated code: output=61b6ea7153ef9940 input=a9049054013a1b77]*/

Modules/_io/iobase.c

@@ -738,11 +738,16 @@ _io__IOBase_readlines_impl(PyObject *self, Py_ssize_t hint)
 _io._IOBase.writelines
     lines: object
     /
+
+Write a list of lines to stream.
+
+Line separators are not added, so it is usual for each of the
+lines provided to have a line separator at the end.
 [clinic start generated code]*/
 
 static PyObject *
 _io__IOBase_writelines(PyObject *self, PyObject *lines)
-/*[clinic end generated code: output=976eb0a9b60a6628 input=432e729a8450b3cb]*/
+/*[clinic end generated code: output=976eb0a9b60a6628 input=cac3fc8864183359]*/
 {
     PyObject *iter, *res;