[Chicago] Question about accessing dictionary's elements.

Sat Sep 19 20:46:32 CEST 2015

Hey Joshua!  I would LOVE to, but I have classes on Wednesday and Thursday
evenings.  So.... ???

On Sat, Sep 19, 2015 at 1:30 PM, Joshua Herman <zitterbewegung at gmail.com>
wrote:

> 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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