ENH: Add context manager `temppath` to manage a temporary file.

Context manager intended for use when the same temporary file needs to
be opened and closed more than once. The context manager creates the
file, closes it, and returns the path to the file. On exit from the
context block the file is removed. The file should be closed before
exiting the context as an error will be raised on windows if not.

Also fix up the `tempdir` context manager to deal with exceptions.

Tests are added for both `temppath` and `tempdir`.

2 files changed, 59 insertions, 5 deletions

diff --git a/numpy/testing/tests/test_utils.py b/numpy/testing/tests/test_utils.py
index 13aeffe02..b558270b3 100644
--- a/numpy/testing/tests/test_utils.py
+++ b/numpy/testing/tests/test_utils.py
@@ -2,6 +2,7 @@ from __future__ import division, absolute_import, print_function
 
 import warnings
 import sys
+import os
 
 import numpy as np
 from numpy.testing import (
@@ -10,7 +11,7 @@ from numpy.testing import (
     assert_warns, assert_no_warnings, assert_allclose, assert_approx_equal,
     assert_array_almost_equal_nulp, assert_array_max_ulp,
     clear_and_catch_warnings, run_module_suite,
-    assert_string_equal
+    assert_string_equal, assert_, tempdir, temppath, 
     )
 import unittest
 
@@ -780,6 +781,36 @@ def test_clear_and_catch_warnings():
     assert_warn_len_equal(my_mod, 2)
 
 
+def test_tempdir():
+    with tempdir() as tdir:
+        fpath = os.path.join(tdir, 'tmp')
+        with open(fpath, 'w'):
+            pass
+    assert_(not os.path.isdir(tdir))
+
+    try:
+        with tempdir() as tdir:
+            raise ValueError()
+    except ValueError:
+        pass
+    assert_(not os.path.isdir(tdir))
+
+
+
+def test_temppath():
+    with temppath() as fpath:
+        with open(fpath, 'w') as f:
+            pass
+    assert_(not os.path.isfile(fpath))
+
+    try:
+        with temppath() as fpath:
+            raise ValueError()
+    except ValueError:
+        pass
+    assert_(not os.path.isfile(fpath))
+
+
 class my_cacw(clear_and_catch_warnings):
 
     class_modules = (sys.modules[__name__],)
diff --git a/numpy/testing/utils.py b/numpy/testing/utils.py
index 00f7ce4d1..e85e2f95f 100644
--- a/numpy/testing/utils.py
+++ b/numpy/testing/utils.py
@@ -12,7 +12,7 @@ import warnings
 from functools import partial
 import shutil
 import contextlib
-from tempfile import mkdtemp
+from tempfile import mkdtemp, mkstemp
 
 from .nosetester import import_nose
 from numpy.core import float32, empty, arange, array_repr, ndarray
@@ -30,7 +30,7 @@ __all__ = ['assert_equal', 'assert_almost_equal', 'assert_approx_equal',
            'assert_', 'assert_array_almost_equal_nulp', 'assert_raises_regex',
            'assert_array_max_ulp', 'assert_warns', 'assert_no_warnings',
            'assert_allclose', 'IgnoreException', 'clear_and_catch_warnings',
-           'SkipTest', 'KnownFailureException']
+           'SkipTest', 'KnownFailureException', 'temppath', 'tempdir']
 
 
 class KnownFailureException(Exception):
@@ -1810,8 +1810,31 @@ def tempdir(*args, **kwargs):
 
     """
     tmpdir = mkdtemp(*args, **kwargs)
-    yield tmpdir
-    shutil.rmtree(tmpdir)
+    try:
+        yield tmpdir
+    finally:
+        shutil.rmtree(tmpdir)
+
+@contextlib.contextmanager
+def temppath(*args, **kwargs):
+    """Context manager for temporary files.
+
+    Context manager that returns the path to a closed temporary file. Its
+    parameters are the same as for tempfile.mkstemp and are passed directly
+    to that function. The underlying file is removed when the context is
+    exited, so it should be closed at that time.
+  
+    Windows does not allow a temporary file to be opened if it is already
+    open, so the underlying file must be closed after opening before it
+    can be opened again.
+
+    """
+    fd, path = mkstemp(*args, **kwargs)
+    os.close(fd)
+    try:
+        yield path
+    finally:
+        os.remove(path)
 
 
 class clear_and_catch_warnings(warnings.catch_warnings):