[Python-checkins] cpython: #1565525: Add traceback.clear_frames() helper function to clear locals ref'd by

Mon Sep 16 00:16:10 CEST 2013

http://hg.python.org/cpython/rev/100606ef02cf
changeset: 85723:100606ef02cf
user: Andrew Kuchling <amk at amk.ca>
date: Sun Sep 15 18:15:56 2013 -0400
summary:
 #1565525: Add traceback.clear_frames() helper function to clear locals ref'd by a traceback
files:
 Doc/library/traceback.rst | 7 ++++++
 Doc/whatsnew/3.4.rst | 8 ++++++
 Lib/test/test_traceback.py | 30 ++++++++++++++++++++++++++
 Lib/traceback.py | 13 ++++++++++-
 Misc/NEWS | 5 ++++
 5 files changed, 62 insertions(+), 1 deletions(-)

diff --git a/Doc/library/traceback.rst b/Doc/library/traceback.rst
--- a/Doc/library/traceback.rst
+++ b/Doc/library/traceback.rst
@@ -129,6 +129,13 @@
 
 A shorthand for ``format_list(extract_stack(f, limit))``.
 
+.. function:: clear_frames(tb)
+
+ Clears the local variables of all the stack frames in a traceback *tb*
+ by calling the :meth:`clear` method of each frame object.
+
+ .. versionadded:: 3.4
+
 
 .. _traceback-example:
 
diff --git a/Doc/whatsnew/3.4.rst b/Doc/whatsnew/3.4.rst
--- a/Doc/whatsnew/3.4.rst
+++ b/Doc/whatsnew/3.4.rst
@@ -377,6 +377,14 @@
 :meth:`sunau.open` now supports the context manager protocol (:issue:`18878`).
 
 
+traceback
+---------
+
+A new :func:`traceback.clear_frames` function takes a traceback object
+and clears the local variables in all of the frames it references,
+reducing the amount of memory consumed (:issue:`1565525`).
+
+
 urllib
 ------
 
diff --git a/Lib/test/test_traceback.py b/Lib/test/test_traceback.py
--- a/Lib/test/test_traceback.py
+++ b/Lib/test/test_traceback.py
@@ -388,6 +388,36 @@
 return s.getvalue()
 
 
+class MiscTracebackCases(unittest.TestCase):
+ #
+ # Check non-printing functions in traceback module
+ #
+
+ def test_clear(self):
+ def outer():
+ middle()
+ def middle():
+ inner()
+ def inner():
+ i = 1
+ 1/0
+
+ try:
+ outer()
+ except:
+ type_, value, tb = sys.exc_info()
+
+ # Initial assertion: there's one local in the inner frame.
+ inner_frame = tb.tb_next.tb_next.tb_next.tb_frame
+ self.assertEqual(len(inner_frame.f_locals), 1)
+
+ # Clear traceback frames
+ traceback.clear_frames(tb)
+
+ # Local variable dict should now be empty.
+ self.assertEqual(len(inner_frame.f_locals), 0)
+
+
 def test_main():
 run_unittest(__name__)
 
diff --git a/Lib/traceback.py b/Lib/traceback.py
--- a/Lib/traceback.py
+++ b/Lib/traceback.py
@@ -7,7 +7,8 @@
 __all__ = ['extract_stack', 'extract_tb', 'format_exception',
 'format_exception_only', 'format_list', 'format_stack',
 'format_tb', 'print_exc', 'format_exc', 'print_exception',
- 'print_last', 'print_stack', 'print_tb']
+ 'print_last', 'print_stack', 'print_tb',
+ 'clear_frames']
 
 #
 # Formatting and printing lists of traceback lines.
@@ -299,3 +300,13 @@
 stack = list(_extract_stack_iter(_get_stack(f), limit=limit))
 stack.reverse()
 return stack
+
+def clear_frames(tb):
+ "Clear all references to local variables in the frames of a traceback."
+ while tb is not None:
+ try:
+ tb.tb_frame.clear()
+ except RuntimeError:
+ # Ignore the exception raised if the frame is still executing.
+ pass
+ tb = tb.tb_next
diff --git a/Misc/NEWS b/Misc/NEWS
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -32,6 +32,11 @@
 faulthandler module if the variable is non-empty. Same behaviour than other
 variables like :envvar:`PYTHONDONTWRITEBYTECODE`.
 
+- Issue #1565525: New function ``traceback.clear_frames`` will clear
+ the local variables of all the stack frames referenced by a traceback
+ object.
+
+
 Tests
 -----
 
-- 
Repository URL: http://hg.python.org/cpython
