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Date: Thu, 08 Dec 2011 16:03:38 +0100
From: Jean-Michel Pichavant <jeanmichel@sequans.com>
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To: Roy Smith <roy@panix.com>
Subject: Re: Misleading error message of the day
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Xref: x330-a1.tempe.blueboxinc.net comp.lang.python:16833

Roy Smith wrote:
> I just spent a while beating my head against this one.
>
> # Python 2.6
>   
>>>> a, b = 'foo'
>>>>         
> Traceback (most recent call last):
>   File "<stdin>", line 1, in <module>
> ValueError: too many values to unpack
>
> The real problem is that there's too *few* values to unpack!  It should 
> have been
>
> a, b = 'foo', 'bar'
>
> I understand why it's generating the exception it does (the string is an 
> iterable), but man, did that message throw off my thought processes and 
> lead me down some totally bogus debugging paths.
>
> It's an unusual case to want to unpack a string.  Maybe the message 
> should changed to "too {many, few} values to unpack (are you sure you 
> wanted to unpack a string?)" if the RHS is a basestring?
>   
string are iterable, considering this, the error is correct.

Values to unpack in 'foo' are 'f', 'o', 'o'

 > a,b,c = 'foo'

 > print a,b,c
f o o


JM