At 10:26 AM 9/29/2007 -0500, Michael Urman wrote:
> This isn't just a matter of dicts; any collection type can be susceptible.
The reason that dicts (and sets) are even worse is that the comparison
could be delayed. If
b"bytes" in [...]
raises an exception, it happens while b"bytes" is still in the
traceback context. With a dictionary, the problem comparison could be
delayed until the next resize. Even if the TypeError did tell you
which dict and (pair of pre-existing) keys were a problem, you still
wouldn't know how those keys got there.
Example data flow:
insert string1 with hash X
insert string2 with hash X -- collision, so it moves to the next slot
del string1
insert bytes with hash X -- replaces the dummy entry, so nothing raised yet
...
insert something utterly unrelated, such as an integer. This
causes a resize, so that now string2 and bytes do collide and raise a
TypeError complaining about strings and bytes -- even though the key
you added is neither.
-jJ
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