[ python-Bugs-1614429 ] dict throwing inaccurate KeyError on small tuple keys

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Bugs item #1614429, was opened at 2006-12-13 02:48
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Category: None
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: toidinamai (toidinamai)
Assigned to: Nobody/Anonymous (nobody)
Summary: dict throwing inaccurate KeyError on small tuple keys

Initial Comment:
When using tuples of length one as keys for the builtin
dictionary the Python runtime raises an inaccurate
KeyError exception that makes some errors hard to find:

Python 2.5 (r25:51908, Dec 12 2006, 18:39:30)
[GCC 4.1.1 (Gentoo 4.1.1-r1)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> {"foo":"bar"}[("foo",)]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
KeyError: 'foo'

Also the error messages for the empty tuple and None are
indistinguishable:

Python 2.5 (r25:51908, Dec 12 2006, 18:39:30)
[GCC 4.1.1 (Gentoo 4.1.1-r1)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> {None:"bar"}[()]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
KeyError
>>> {():"bar"}[None]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
KeyError

This also seems to be the case for earlier versions of Python.

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