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The menu option *File / Path browser* (as well in the *Shell* window as in the *Editor* one) shows a new window with a tree structure rooted at *sys.path*. The available leaf nodes show the *plus* sign that usually implies that they can be expanded by clicking on the desired one. On the performance of this action IDLE disappears immediately. If one clicks just on the legend of the node, IDLE remains undisturbed but nothing more happens.
Idle's help says:
*File Menu:
...
Path Browser -- Show sys.path directories, modules, classes and methods*
so that apparently the expansion should also work.
I suppose that this command would be mostly used at the initial phases of learning Python (at least I would have done it if I had noticed then its existence and function), but its present status does not favor such didactic purpose.
Regards

Thank you for the report. There does seem to be a regression in the 3.3 version of IDLE. Using the OS X version of bin/idle3.3 and selecting menu item File -> Path Browser results in the following exception:
Exception in Tkinter callback
Traceback (most recent call last):
 File "/Library/Frameworks/Python.framework/Versions/3.3/lib/python3.3/tkinter/__init__.py", line 1442, in __call__
 return self.func(*args)
 File "/Library/Frameworks/Python.framework/Versions/3.3/lib/python3.3/idlelib/TreeWidget.py", line 131, in expand
 self.update()
 File "/Library/Frameworks/Python.framework/Versions/3.3/lib/python3.3/idlelib/TreeWidget.py", line 164, in update
 self.parent.update()
 File "/Library/Frameworks/Python.framework/Versions/3.3/lib/python3.3/idlelib/TreeWidget.py", line 170, in update
 self.draw(7, 2)
 File "/Library/Frameworks/Python.framework/Versions/3.3/lib/python3.3/idlelib/TreeWidget.py", line 197, in draw
 cy = child.draw(cx, cy)
 File "/Library/Frameworks/Python.framework/Versions/3.3/lib/python3.3/idlelib/TreeWidget.py", line 184, in draw
 sublist = self.item._GetSubList()
 File "/Library/Frameworks/Python.framework/Versions/3.3/lib/python3.3/idlelib/TreeWidget.py", line 338, in _GetSubList
 sublist = self.GetSubList()
 File "/Library/Frameworks/Python.framework/Versions/3.3/lib/python3.3/idlelib/PathBrowser.py", line 61, in GetSubList
 for nn, name in self.listmodules(names):
 File "/Library/Frameworks/Python.framework/Versions/3.3/lib/python3.3/idlelib/PathBrowser.py", line 78, in listmodules
 for suff, mode, flag in suffixes:
ValueError: too many values to unpack (expected 3)

Here's the revision that broke it: b81ddaf0db47
The 2.7 branch still uses imp.get_suffixes, whereas the 3.3 and 3.4 uses this importlib construct.
The imp.get_suffixes returns a list of tuples of 3 items: (suffix, mode, type). The current code only returns what would be the first item of that tuple. The for-loop only uses that first item anyway, so the tuple unpacking can be removed safely.
The attached patch fixes the issue. It also includes a basic unit test within the idlelib/test directory. We need to get the unittest framework started for IDLE, as given in issue15392.

New changeset d369e50677a6 by Ned Deily in branch '3.3':
Issue #16226: Fix IDLE Path Browser crash.
http://hg.python.org/cpython/rev/d369e50677a6
New changeset 58f9523cf407 by Ned Deily in branch 'default':
Issue #16226: Fix IDLE Path Browser crash.
http://hg.python.org/cpython/rev/58f9523cf407 

I've committed Roger's fix for release in 3.3.1 and 3.4.0. Thanks, Roger. I did not apply the proposed test since, as it stands, it would never be run by test.regrtest without establishing a idlelib test runner infrastructure as proposed by Issue15392. I'm attaching the test as a separate patch and will add a comment to 15392 that the test should be added.

Test has been committed on all three branches as part of #15392 

This patch does 
1.Remove pep8 violations in PathBrowser.py . Replaces "file","dir","sorted" by "file_","dir_","sorted_" respectively.
2.Extends test coverage for PathBrowser.py in idle_test/test_PathBrowser.py
New modules now under tests include
1.dirBrowserTreeItem - getText,ispackagedir
2.pathBrowserTreeItem - getText,getSublist
Only method missing a test after this patch will be listmodules.I am not too sure whether it requires a test for itself.it is indirectly being tested from lines 8 and 9(in the current tip).

S.H. moved his patch for new tests to new issue #20792.