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Loop thru the dictionary with tuples

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  Loop thru the dictionary with tuples Igor Korot <ikorot01@gmail.com> - 2014-05-25 05:55 -0700
    Re: Loop thru the dictionary with tuples Paul Rubin <no.email@nospam.invalid> - 2014-05-25 05:59 -0700
      Re: Loop thru the dictionary with tuples Tim Chase <python.list@tim.thechases.com> - 2014-05-25 08:07 -0500
    Re: Loop thru the dictionary with tuples Roy Smith <roy@panix.com> - 2014-05-25 09:22 -0400
      Re: Loop thru the dictionary with tuples Chris Angelico <rosuav@gmail.com> - 2014-05-25 23:58 +1000

#72001 — Loop thru the dictionary with tuples

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.

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#72003

Igor Korot <ikorot01@gmail.com> writes:
> for (key,value) in my_dict:
>     #Do some stuff
>
> but I'm getting an error "Too many values to unpack".

Use 
    for (key,value) in mydict.iteritems(): ...
otherwise you loop through just the keys, whicn in your dictionary 
happens to be 3-tuples.  So you try to unpack a 3-tuple to a 2-tuple
and get a too-many-values error.

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#72004

[Multipart message — attachments visible in raw view] — view raw

On 2014-05-25 05:59, Paul Rubin wrote:
> Igor Korot <ikorot01@gmail.com> writes:
> > for (key,value) in my_dict:
> >     #Do some stuff
> >
> > but I'm getting an error "Too many values to unpack".
> 
> Use 
>     for (key,value) in mydict.iteritems(): ...

You can even use

  for ((k1,k2,k3), value) in mydict.iteritems():
    ...

if you need to unpack the key at the same time.

-tkc

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#72005

In article <mailman.10291.1401022510.18130.python-list@python.org>,
 Igor Korot <ikorot01@gmail.com> wrote:

> for (key,value) in my_dict:
>     #Do some stuff
> 
> but I'm getting an error "Too many values to unpack".

Several people have already given you the right answer, so I'll just 
suggest a general debugging technique.  Break this down into the 
smallest possible steps and print out the intermediate values.  When you 
write:

> for (key,value) in my_dict:

two things are happening.  One is that you're iterating over my_dict, 
the other is that you're unpacking the iterated-over things.  So break 
those up into individual steps:

for thing in my_dict:
    (key, value) = thing

and see what that gives you.  Do you still get an error?  If so, does it 
occur on the "for" line or on the assignment line?  Hint: in this case, 
it will happen on the assignment line, so, your next step is to print 
everything out and see what's going on:

for thing in my_dict:
    print thing
    (key, value) = thing

At this point, it should be obvious what's going on, but just in case 
it's not, sometimes I find it useful to be even more verbose:

for thing in my_dict:
    print type(thing), repr(thing)
    (key, value) = thing

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#72009

On Sun, May 25, 2014 at 11:22 PM, Roy Smith <roy@panix.com> wrote:
> Hint: in this case,
> it will happen on the assignment line, so, your next step is to print
> everything out and see what's going on:
>
> for thing in my_dict:
>     print thing
>     (key, value) = thing

Aside: I know that you (Roy) are still using Python 2, but the OP
could be on either branch. As a matter of safety, I'd put parens
around the print:

for thing in my_dict:
    print(thing)
    (key, value) = thing

That way, it works on either.

ChrisA

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