roy at panix.com
Sun Jul 29 16:23:59 CEST 2012
In article <81818a9c-60d3-48da-9345-0c0dfd5b25e7 at googlegroups.com>,
subhabangalore at gmail.com wrote:
> the code was running fine, but all on a sudden started to give the following
> TypeError: unhashable type: 'list'
First, make sure you understand what the error means. All the elements
of a set must be hashable. Lists are not hashable because they are
mutable. So, what the error is telling you is that some element of
list1 is itself a list, and therefore not hashable, and thus the set
can't be created.
I would start by printing list1. If the list is long (or contains
deeply nested structures), just doing "print list1" may result in
something that is difficult to read. In that case, try using pprint
(see the pprint module) to get a nicer display.
If it's still not obvious, pull out the bigger guns. Try something like:
for item in list1:
print "This one can't be hashed: %s" % item
> And sometimes some good running program gives error all on a sudden with no
> parameter changed
Well, *something* changed. Assuming nothing truly bizarre like a stray
Higgs Boson flipping a bit in your computer's memory, what you need to
do is figure out what that is. Did you change your code in any way
(having everything under version control helps here)? If not the code,
then what changed about the input?
If you're sure that both the code and the input are unchanged, that
leaves something in the environment. Did your python interpreter get
upgraded to a newer version? Or your operating system? PYTHONPATH?
Depending on what your program is doing, it could be something time
based. A different time zone, perhaps? Did daylight savings time just
go into or out of effect where you are? Does it only fail on Sunday?
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