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To: python-list@python.org
From: Ned Batchelder <ned@nedbatchelder.com>
Subject: Re: Loop thru the dictionary with tuples
Date: Sun, 25 May 2014 22:13:57 -0400
References: <CA+FnnTwpQKTyvROYq32YsDfwDooDXRbRg-SYGGhFs1T1D9o_Ow@mail.gmail.com> <llsstb$1sa$1@ger.gmane.org> <llu7ni$dph$1@ger.gmane.org>
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On 5/25/14 10:09 PM, Dave Angel wrote:
> Ned Batchelder <ned@nedbatchelder.com> Wrote in message:
>> On 5/25/14 8:55 AM, Igor Korot wrote:
>>> Hi, ALL,
>>> I have a following data structure:
>>>
>>> my_dict[(var1,var2,var3)] = None
>>> my_dict[(var4,var5,var6)] = 'abc'
>>>
>>> What I'm trying to do is this:
>>>
>>> for (key,value) in my_dict:
>>>       #Do some stuff
>>>
>>> but I'm getting an error "Too many values to unpack".
>>>
>>> What am I doing wrong?
>>>
>>> Thank you.
>>>
>>
>> You want:
>>
>>       for key, value in my_dict.items():  # or .iteritems()
>>
>> Iterating over a dictionary gives you its keys.  items() will give you
>> key,value pairs.
>
>
> Or, if the dict is large,  you might want
>
> for key in my_dict:
>      value = my_dict [key]
>      ...

For a large dict, .iteritems (Python 2) or .items (Python 3) are 
perfectly fine and don't have a cost to avoid.   .items (Python 2) 
produces a list, which would be bad.

-- 
Ned Batchelder, http://nedbatchelder.com