[Chicago] Question about accessing dictionary's elements.

[Joshua Herman]

Hey I'm doing machine learning too why don't you come to one of the python
meet ups in Chicago

On Sat, Sep 19, 2015 at 12:56 PM Lewit, Douglas <d-lewit at neiu.edu> wrote:

> Hi William,
>
> I'm doing a KNN program (K-Nearest-Neighbors).  I'm attaching what I've
> done so far.  It's not complete!  But I've made good progress I think.
>  (The program won't work unless you also download the .txt file that the
> program uses to read in the data.)
>
> For this problem the data has to get split into two sets: a training set
> (kind of like a control group in an experiment) and the test set (the
> experimental group or its equivalent).  I have to use the K smallest
> normalized distances to make a guess about which class the records in the
> Training Set belong to.  (There are six classes: {1, 2, 3, 5, 6, 7}.
> There's no class #4.)
>
> This problem has given me a massive headache, but I think I'm almost done
> with it.  All that's left really is to use one of the algorithms to make a
> decision about which class each Test record should be assigned to.
>
> Thanks for the feedback!
>
> Best,
>
> Douglas.
>
>
> On Sat, Sep 19, 2015 at 10:45 AM, William E. S. Clemens <
> wesclemens at gmail.com> wrote:
>
>> I would agree that Jimmy's solution is the correct one for doing this.
>> But I would avoid setting up your data structure in this manner. A dict is
>> a hash table and it is be extremely fast a looking up a value by key.
>>
>> You are building an array of the keys to linearly search. This operation
>> is going to be slow and will not scale well. If you described what this
>> data is and what your trying todo with it. I maybe able to suggest a better
>> data structure for storing and accessing it.
>>
>>
>>
>>
>> --
>> William Clemens
>> Phone: 847.485.9455
>> E-mail: wesclemens at gmail.com
>>
>> On Sat, Sep 19, 2015 at 10:02 AM, Lewit, Douglas <d-lewit at neiu.edu>
>> wrote:
>>
>>> I love it!  Thanks Jim.
>>>
>>> On Sat, Sep 19, 2015 at 8:09 AM, Jimmy Calahorrano via Chicago <
>>> chicago at python.org> wrote:
>>>
>>>> is more elegant but not sure if is the best option:
>>>>
>>>>
>>>> [A[key] for key in A.keys() if key[0] == 1]
>>>>
>>>>
>>>>
>>>> --------------------------------------------
>>>> On Sat, 9/19/15, Lewit, Douglas <d-lewit at neiu.edu> wrote:
>>>>
>>>>  Subject: [Chicago] Question about accessing dictionary's elements.
>>>>  To: "The Chicago Python Users Group" <chicago at python.org>
>>>>  Date: Saturday, September 19, 2015, 7:43 AM
>>>>
>>>>  Hi
>>>>  guys,
>>>>  I have a problem and not
>>>>  sure how to address it.  Let's say I have a simple
>>>>  dictionary such as.
>>>>  A = { (1, 2) : 10, (1, 3) :
>>>>  15, (1, 4) : 50, (2, 0) : 2, (2, 5) : 8, (2, 12) : 19
>>>>  }
>>>>  I would like to access any
>>>>  and all tuples whose first value is 1 or let's say 2.
>>>>  How would I do that?
>>>>  So what I'm trying to
>>>>  go for is:
>>>>  A[(1, placeholder for any
>>>>  int value)] thus giving me all the values that correspond to
>>>>  (1, #).  Not really sure how to go about this.  Unless....
>>>>  I suppose I could do something like
>>>>  this:
>>>>  for key in
>>>>  A:     if list(key)[0]
>>>>  == 1:
>>>>  print(A[key])  #### Or whatever I want to do with the
>>>>  number.
>>>>  Hmmm.... maybe that would
>>>>  work, but is there a more "elegant" way to do
>>>>  this?  Is there any "pattern matching" in Python
>>>>  so that I could do this:
>>>>  A[(1, #placeholder for any
>>>>  int )]
>>>>  Hey, thanks for your
>>>>  help.
>>>>  By the way, has anyone seen
>>>>  the book LEARNING PYTHON by Mark Lutz?  Wow!  Full of
>>>>  great information, but the book is HUGE!!!  I'll have
>>>>  serious back problems if I carry that thing around in my
>>>>  backpack!  There's something about small, lightweight
>>>>  books that I really prefer.  (And then there's eBooks,
>>>>  but that's a horse of a different color in my
>>>>  opinion.)
>>>>  Have a great weekend and
>>>>  I'm looking forward to some ideas on the above
>>>>  problem.  Thanks in advance.
>>>>  Best,
>>>>  Douglas
>>>>  L.
>>>>
>>>>  -----Inline Attachment Follows-----
>>>>
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>>>
>>>
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