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Re: Python Error

From Peter Otten <__peter__@web.de>
Subject Re: Python Error
Date 2012-07-29 13:08 +0200
Organization None
References <81818a9c-60d3-48da-9345-0c0dfd5b25e7@googlegroups.com>
Newsgroups comp.lang.python
Message-ID <mailman.2680.1343560135.4697.python-list@python.org> (permalink)

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subhabangalore@gmail.com wrote:

> Dear Group,
> 
> I was trying to convert the list to a set, with the following code:
> 
> set1=set(list1)
> 
> the code was running fine, but all on a sudden started to give the
> following error,
> 
> set1=set(list1)
> TypeError: unhashable type: 'list'
> 
> please let me know how may I resolve.
> 
> And sometimes some good running program gives error all on a sudden with
> no parameter changed, how may I debug it?

Add a print statement before the offending line:

print list1
set1 = set(list1)

You will see that list1 contains another list, e. g. this works...

>>> list1 = ["alpha", "beta"]                                                                                                                                                                                     
>>> set(list1)                                                                                                                                                                                                    
set(['alpha', 'beta'])                                                                                                                                                                                            

...while this doesn't:

>>> list1 = ["alpha", ["beta"]]                                                                                                                                                                                   
>>> set(list1)                                                                                                                                                                                   
Traceback (most recent call last):                                                                                                                                                                                
  File "<stdin>", line 1, in <module>                                                                                                                                                                             
TypeError: unhashable type: 'list'

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Python Error subhabangalore@gmail.com - 2012-07-29 02:27 -0700
  Re: Python Error Peter Otten <__peter__@web.de> - 2012-07-29 13:08 +0200
  Re: Python Error subhabangalore@gmail.com - 2012-07-29 05:30 -0700
    Re: Python Error Thomas Jollans <t@jollybox.de> - 2012-07-29 14:45 +0200
    Re: Python Error Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-07-29 14:53 +0100
    Re: Python Error Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-07-29 14:01 +0000
    Re: Python Error Emile van Sebille <emile@fenx.com> - 2012-07-29 07:42 -0700
  Re: Python Error Roy Smith <roy@panix.com> - 2012-07-29 10:23 -0400
    Re: Python Error subhabangalore@gmail.com - 2012-07-29 07:41 -0700
  Re: Python Error Jürgen A. Erhard <jae@jaerhard.com> - 2012-07-29 15:57 +0200
    Re: Python Error Duncan Booth <duncan.booth@invalid.invalid> - 2012-07-30 11:15 +0000
  Re: Python Error subhabangalore@gmail.com - 2012-07-29 07:36 -0700
    Re: Python Error Chris Angelico <rosuav@gmail.com> - 2012-07-30 01:12 +1000

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