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-rw-r--r--Doc/library/io.rst8
1 files changed, 6 insertions, 2 deletions
diff --git a/Doc/library/io.rst b/Doc/library/io.rst
index 753e6c1..97a7064 100644
--- a/Doc/library/io.rst
+++ b/Doc/library/io.rst
@@ -1052,8 +1052,12 @@ Text I/O
The initial value of the buffer can be set by providing *initial_value*.
If newline translation is enabled, newlines will be encoded as if by
- :meth:`~TextIOBase.write`. The stream is positioned at the start of
- the buffer.
+ :meth:`~TextIOBase.write`. The stream is positioned at the start of the
+ buffer which emulates opening an existing file in a `w+` mode, making it
+ ready for an immediate write from the beginning or for a write that
+ would overwrite the initial value. To emulate opening a file in an `a+`
+ mode ready for appending, use `f.seek(0, io.SEEK_END)` to reposition the
+ stream at the end of the buffer.
The *newline* argument works like that of :class:`TextIOWrapper`,
except that when writing output to the stream, if *newline* is ``None``,