inspect.stack() should return list of named tuples

[danielsh]

BPO	16808
Nosy	@rhettinger, @terryjreedy, @pitrou, @meadori, @PCManticore, @1st1
Files	inspect-v1.diff inspect-v2.diff inspect-v3.diff inspect-v5.diff

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2014-08-24.14:55:31.887>
created_at = <Date 2012-12-29.03:02:29.153>
labels = ['easy', 'type-feature', 'library']
title = 'inspect.stack() should return list of named tuples'
updated_at = <Date 2014-08-24.14:55:31.886>
user = 'https://bugs.python.org/danielsh'

bugs.python.org fields:

activity = <Date 2014-08-24.14:55:31.886>
actor = 'pitrou'
assignee = 'none'
closed = True
closed_date = <Date 2014-08-24.14:55:31.887>
closer = 'pitrou'
components = ['Library (Lib)']
creation = <Date 2012-12-29.03:02:29.153>
creator = 'danielsh'
dependencies = []
files = ['28475', '28488', '28515', '28572']
hgrepos = []
issue_num = 16808
keywords = ['patch', 'easy']
message_count = 11.0
messages = ['178467', '178478', '178485', '178549', '178709', '178713', '179099', '179100', '179106', '225823', '225824']
nosy_count = 9.0
nosy_names = ['rhettinger', 'terry.reedy', 'pitrou', 'meador.inge', 'Claudiu.Popa', 'python-dev', 'yselivanov', 'danielsh', 'davet']
pr_nums = []
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue16808'
versions = ['Python 3.5']

[danielsh]

Currently inspect.stack() returns a list of 6-tuples. I suggest to make it return a list of named tuples, so code that only needs one tuple element can get it by name.

Current behaviour:
% ./python -c 'import inspect; print(inspect.stack()[0])'
(<frame object at 0x157fb38>, '<string>', 1, '<module>', None, None)

Suggested behaviour:
% ./python -c 'import inspect; print(inspect.stack()[0])'
FrameInfo(frame=<frame object at 0xddab38>, filename='<string>', lineno=1, function='<module>', code_context=None, index=None)

[rhettinger]

+1

[danielsh]

Why did you set stage to 'needs patch'? One is already attached.

[danielsh]

Add versionchanged per review.

[meadori]

This patch looks good to me with the exception that "versionchanged" should be 3.4.

[danielsh]

Fixed that in v3.

[terryjreedy]

Should a test be added to or changed in test_inspect? Line 163 has a test_stack method that calls inspect.stack.

[meadori]

I suppose asserting the type wouldn't hurt, but I don't consider it that important:

--- a/Lib/test/test_inspect.py
+++ b/Lib/test/test_inspect.py
@@ -164,12 +164,16 @@ class TestInterpreterStack(IsTestBase):
         self.assertTrue(len(mod.st) >= 5)
         self.assertEqual(revise(*mod.st[0][1:]),
              (modfile, 16, 'eggs', ['    st = inspect.stack()\n'], 0))
+        self.assertIsInstance(mod.st[0], inspect.FrameInfo)
         self.assertEqual(revise(*mod.st[1][1:]),
              (modfile, 9, 'spam', ['    eggs(b + d, c + f)\n'], 0))
+        self.assertIsInstance(mod.st[1], inspect.FrameInfo)
         self.assertEqual(revise(*mod.st[2][1:]),
              (modfile, 43, 'argue', ['            spam(a, b, c)\n'], 0))
+        self.assertIsInstance(mod.st[2], inspect.FrameInfo)
         self.assertEqual(revise(*mod.st[3][1:]),
              (modfile, 39, 'abuse', ['        self.argue(a, b, c)\n'], 0))
+        self.assertIsInstance(mod.st[3], inspect.FrameInfo)

TestGetClosureVars builds the named tuples directly and compares them. For example:

        expected = inspect.ClosureVars(nonlocal_vars, global_vars,
                                       builtin_vars, unbound_names)
        self.assertEqual(inspect.getclosurevars(f(_arg)), expected)

Doing this for FrameInfo is awkward because we don't have a frame object to construct
the named tuple with.

[danielsh]

Terry J. Reedy wrote on Sat, Jan 05, 2013 at 01:33:50 +0000:

Should a test be added to or changed in test_inspect? Line 163 has
a test_stack method that calls inspect.stack.

Makes sense; added a test that tests named attribute access. Thanks for
the pointer.

[python-dev]

New changeset d03730abd2f6 by Antoine Pitrou in branch 'default':
Issue bpo-16808: inspect.stack() now returns a named tuple instead of a tuple.
http://hg.python.org/cpython/rev/d03730abd2f6

[pitrou]

It seems like this patch had been overlooked. I refreshed it for 3.5, added a couple tests, and pushed it. Thank you, Daniel!