Issue #12922: fix the TextIOBase documentation to include a description of seek() and tell() methods.
diff --git a/Doc/library/io.rst b/Doc/library/io.rst
index 972820c..becc4a2 100644
--- a/Doc/library/io.rst
+++ b/Doc/library/io.rst
@@ -704,6 +704,32 @@
Read until newline or EOF and return a single ``str``. If the stream is
already at EOF, an empty string is returned.
+ .. method:: seek(offset, whence=SEEK_SET)
+
+ Change the stream position to the given *offset*. Behaviour depends
+ on the *whence* parameter:
+
+ * :data:`SEEK_SET` or ``0``: seek from the start of the stream
+ (the default); *offset* must either be a number returned by
+ :meth:`TextIOBase.tell`, or zero. Any other *offset* value
+ produces undefined behaviour.
+ * :data:`SEEK_CUR` or ``1``: "seek" to the current position;
+ *offset* must be zero, which is a no-operation (all other values
+ are unsupported).
+ * :data:`SEEK_END` or ``2``: seek to the end of the stream;
+ *offset* must be zero (all other values are unsupported).
+
+ Return the new absolute position as an opaque number.
+
+ .. versionadded:: 3.1
+ The ``SEEK_*`` constants.
+
+ .. method:: tell()
+
+ Return the current stream position as an opaque number. The number
+ does not usually represent a number of bytes in the underlying
+ binary storage.
+
.. method:: write(s)
Write the string *s* to the stream and return the number of characters