gh-107801: Document io.TextIOWrapper.tell (#108265)

Author: erlend-aasland

Doc/library/io.rst

@@ -1054,13 +1054,21 @@ Text I/O
 
       * ``seek(0, SEEK_SET)``: Rewind to the start of the stream.
       * ``seek(cookie, SEEK_SET)``: Restore a previous position;
-        *cookie* **must be** a number returned by :meth:`!tell`.
+        *cookie* **must be** a number returned by :meth:`tell`.
       * ``seek(0, SEEK_END)``: Fast-forward to the end of the stream.
       * ``seek(0, SEEK_CUR)``: Leave the current stream position unchanged.
 
       Any other argument combinations are invalid,
       and may raise exceptions.
 
+   .. method:: tell()
+
+      Return the stream position as an opaque number.
+      The return value of :meth:`!tell` can be given as input to :meth:`seek`,
+      to restore a previous stream position.
+
+
+
 .. class:: StringIO(initial_value='', newline='\n')
 
    A text stream using an in-memory text buffer.  It inherits

Modules/_io/clinic/textio.c.h

@@ -2640,11 +2640,16 @@ _io_TextIOWrapper_seek_impl(textio *self, PyObject *cookieObj, int whence)
 
 /*[clinic input]
 _io.TextIOWrapper.tell
+
+Return the stream position as an opaque number.
+
+The return value of tell() can be given as input to seek(), to restore a
+previous stream position.
 [clinic start generated code]*/
 
 static PyObject *
 _io_TextIOWrapper_tell_impl(textio *self)
-/*[clinic end generated code: output=4f168c08bf34ad5f input=9a2caf88c24f9ddf]*/
+/*[clinic end generated code: output=4f168c08bf34ad5f input=0852d627d76fb520]*/
 {
     PyObject *res;
     PyObject *posobj = NULL;