#26001: mention in the tutorial that files in binary mode expect bytes, not str.
diff --git a/Doc/tutorial/inputoutput.rst b/Doc/tutorial/inputoutput.rst
index c157f22..5314fed 100644
--- a/Doc/tutorial/inputoutput.rst
+++ b/Doc/tutorial/inputoutput.rst
@@ -271,10 +271,11 @@
``f`` has already been created.
To read a file's contents, call ``f.read(size)``, which reads some quantity of
-data and returns it as a string or bytes object. *size* is an optional numeric
-argument. When *size* is omitted or negative, the entire contents of the file
-will be read and returned; it's your problem if the file is twice as large as
-your machine's memory. Otherwise, at most *size* bytes are read and returned.
+data and returns it as a string (in text mode) or bytes object (in binary mode).
+*size* is an optional numeric argument. When *size* is omitted or negative, the
+entire contents of the file will be read and returned; it's your problem if the
+file is twice as large as your machine's memory. Otherwise, at most *size* bytes
+are read and returned.
If the end of the file has been reached, ``f.read()`` will return an empty
string (``''``). ::
@@ -315,11 +316,11 @@
>>> f.write('This is a test\n')
15
-To write something other than a string, it needs to be converted to a string
-first::
+Other types of objects need to be converted -- either to a string (in text mode)
+or a bytes object (in binary mode) -- before writing them::
>>> value = ('the answer', 42)
- >>> s = str(value)
+ >>> s = str(value) # convert the tuple to string
>>> f.write(s)
18