#1286: allow using fileinput.FileInput as context manager.
diff --git a/Doc/library/fileinput.rst b/Doc/library/fileinput.rst
index d98a198..eac324d 100644
--- a/Doc/library/fileinput.rst
+++ b/Doc/library/fileinput.rst
@@ -24,7 +24,7 @@
All files are opened in text mode by default, but you can override this by
specifying the *mode* parameter in the call to :func:`.input` or
-:class:`FileInput()`. If an I/O error occurs during opening or reading a file,
+:class:`FileInput`. If an I/O error occurs during opening or reading a file,
:exc:`IOError` is raised.
If ``sys.stdin`` is used more than once, the second and further use will return
@@ -54,6 +54,16 @@
during iteration. The parameters to this function will be passed along to the
constructor of the :class:`FileInput` class.
+ The :class:`FileInput` instance can be used as a context manager in the
+ :keyword:`with` statement. In this example, *input* is closed after the
+ :keyword:`with` statement is exited, even if an exception occurs::
+
+ with fileinput.input(files=('spam.txt', 'eggs.txt')) as input:
+ process(input)
+
+ .. versionchanged:: 3.2
+ Can be used as a context manager.
+
The following functions use the global state created by :func:`fileinput.input`;
if there is no active state, :exc:`RuntimeError` is raised.
@@ -132,13 +142,23 @@
*filename* and *mode*, and returns an accordingly opened file-like object. You
cannot use *inplace* and *openhook* together.
+ A :class:`FileInput` instance can be used as a context manager in the
+ :keyword:`with` statement. In this example, *input* is closed after the
+ :keyword:`with` statement is exited, even if an exception occurs::
-**Optional in-place filtering:** if the keyword argument ``inplace=1`` is passed
-to :func:`fileinput.input` or to the :class:`FileInput` constructor, the file is
-moved to a backup file and standard output is directed to the input file (if a
-file of the same name as the backup file already exists, it will be replaced
-silently). This makes it possible to write a filter that rewrites its input
-file in place. If the *backup* parameter is given (typically as
+ with FileInput(files=('spam.txt', 'eggs.txt')) as input:
+ process(input)
+
+ .. versionchanged:: 3.2
+ Can be used as a context manager.
+
+
+**Optional in-place filtering:** if the keyword argument ``inplace=True`` is
+passed to :func:`fileinput.input` or to the :class:`FileInput` constructor, the
+file is moved to a backup file and standard output is directed to the input file
+(if a file of the same name as the backup file already exists, it will be
+replaced silently). This makes it possible to write a filter that rewrites its
+input file in place. If the *backup* parameter is given (typically as
``backup='.<some extension>'``), it specifies the extension for the backup file,
and the backup file remains around; by default, the extension is ``'.bak'`` and
it is deleted when the output file is closed. In-place filtering is disabled
diff --git a/Lib/fileinput.py b/Lib/fileinput.py
index 90a600b..a25a021 100644
--- a/Lib/fileinput.py
+++ b/Lib/fileinput.py
@@ -238,6 +238,12 @@
self.nextfile()
self._files = ()
+ def __enter__(self):
+ return self
+
+ def __exit__(self, type, value, traceback):
+ self.close()
+
def __iter__(self):
return self
diff --git a/Lib/test/test_fileinput.py b/Lib/test/test_fileinput.py
index aae16ea..f312882 100644
--- a/Lib/test/test_fileinput.py
+++ b/Lib/test/test_fileinput.py
@@ -231,6 +231,30 @@
## finally:
## remove_tempfiles(t1)
+ def test_context_manager(self):
+ try:
+ t1 = writeTmp(1, ["A\nB\nC"])
+ t2 = writeTmp(2, ["D\nE\nF"])
+ with FileInput(files=(t1, t2)) as fi:
+ lines = list(fi)
+ self.assertEqual(lines, ["A\n", "B\n", "C", "D\n", "E\n", "F"])
+ self.assertEqual(fi.filelineno(), 3)
+ self.assertEqual(fi.lineno(), 6)
+ self.assertEqual(fi._files, ())
+ finally:
+ remove_tempfiles(t1, t2)
+
+ def test_close_on_exception(self):
+ try:
+ t1 = writeTmp(1, [""])
+ with FileInput(files=t1) as fi:
+ raise IOError
+ except IOError:
+ self.assertEqual(fi._files, ())
+ finally:
+ remove_tempfiles(t1)
+
+
def test_main():
run_unittest(BufferSizesTests, FileInputTests)
diff --git a/Misc/NEWS b/Misc/NEWS
index 2886e61..768c7df 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -15,6 +15,8 @@
Library
-------
+- Issue #1286: Allow using fileinput.FileInput as a context manager.
+
- Add lfu_cache() and lru_cache() decorators to the functools module.