[Tutor] Mapping ID's for corresponding values in different Columns

[Fred G]

Sorry, just got that as well.  It was the placement of the if-statement in
the nested for-loop.  so v was stuck on 3...thanks again for the help with
this!!!

On Mon, Jul 9, 2012 at 1:57 PM, Fred G <bayespokerguy at gmail.com> wrote:

> Got it! Thanks guys for all your help--what a satisfying feeling!  Just
> out of curiosity, in the following:
>
> def new_dict (csv_to_dict, nested_line):
>     old_dict = csv_to_dict(file1)
>     old_list = nested_line(file2)
>     new_dict = {}
>     #for item in old_list:
>     #    new_dict[item] = item
>     for k, v in old_dict.iteritems():
>         for item in old_list:
>             if k == item:
>                 new_dict[item] = v
>     return (new_dict)
>
> when I deleted the third line from the bottom (the "if k == item"), I got
> the same value ("3") for each key, instead of the correct output (ie the
> different ID's).  Does anyone know why this was the case?
>
> Thanks so much.
>
>
> On Mon, Jul 9, 2012 at 8:23 AM, Fred G <bayespokerguy at gmail.com> wrote:
>
>> Thank you guys so much.  I'm quite close now, but I'm having a bit of
>> trouble on the final for-loop to create the new dictionary.  I have the
>> following 3 functions (note I'm re-typing it from a different computer so
>> while the identation will be off here, it is correct in the actual code):
>>
>> #read in file as dictionary.  Name is key, id is value.
>> def csv_to_dict(filename):
>>   record = {}
>>   line = filename.readline()
>>   for line in filename:
>>     key = line.split(",", 1)[-1]
>>     val = line.split(",", 1)[:-1]
>>   return record
>>
>> #read in file2 names
>> def nested_line(filename):
>>   line = filename.readline()
>>   new_list = []
>>   for line in filename:
>>     name = line.split(",", 1)[-1]
>>     new_list.append(name)
>>   return new_list
>>
>> #this is the function that I'm having trouble with
>> #create new dict mapping file 1 ids to file2's names
>> def new_dict (csv_to_dict, nested_line):
>>   old_dict = cssv_to_dict(file1)
>>   old_list = nested_line(file2)
>>   new_dict1 = {}
>>   for item in old_list:
>>     new_dict1[item] = item
>>   return (new_dict1)
>>
>> I have tried various permutations of the for loop in this final function,
>> but I haven't quite gotten it.  The current form is the closest I have
>> gotten to my desired output, since it produces the new dictionary with the
>> name that I want-- just an invalid id associated with that name.  I tried a
>> bunch of different nested loops but kept getting it incorrect and then
>> after so many attempts I got a little confused about what I was trying to
>> do.  So I backed up a little bit and have this.
>>
>> Conceptually, I thought that this would give me my desired result:
>> new_dict
>> for name in old_list:
>>   for key, value in old_dict:
>>     if name == key:
>>       new_dict1[key] = value
>> return(new_dict1)
>>
>> But it wasn't right.  I tried a different approach where I used the
>> dict.values() function in order to pull out the values from old_dict that
>> we want to include in the new_dict, but I got a bit lost there, too.
>>
>> I'm so close right now and I would be so thankful for any bit of
>> clarification which could get me to the finish line.
>>
>> On Mon, Jul 9, 2012 at 12:42 AM, Hugo Arts <hugo.yoshi at gmail.com> wrote:
>>
>>> On Sun, Jul 8, 2012 at 11:47 PM, Fred G <bayespokerguy at gmail.com> wrote:
>>>
>>>> Hi--
>>>>
>>>> My current input looks like the following:
>>>>
>>>> FILE1.csv
>>>> PERSON_ID    PERSON_NAME
>>>> 1                     Jen
>>>> 2                     Mike
>>>> 3                     Jim
>>>> 4
>>>> 5                     Jane
>>>> 6                     Joe
>>>> 7                     Jake
>>>>
>>>> FILE2.csv
>>>> PERSON_ID   PERSON_NAME
>>>>                      Jim
>>>>                      Mike
>>>>                      Jane
>>>>                      Todd
>>>>                      Jen
>>>>
>>>> _________
>>>> I want to fill into the PERSON_ID column of FILE2.csv the corresponding
>>>> ID's associated with those names as identified in FILE1.csv.
>>>>
>>>> At first I imported the csv module and was using the csv.Reader, but
>>>> then it seemed simple enough just to write something like:
>>>> for line in file2:
>>>>      print(line)
>>>>
>>>> giving me the following output:
>>>> PERSON_ID, PERSON_NAME
>>>> , Jim
>>>> , Mike
>>>> , Jane
>>>> , Todd
>>>> , Jen
>>>>
>>>> I think I understand the issue at a conceptual level, but not quite
>>>> sure how to fully implement it:
>>>> a) I want to build a dictionary to create keys, such that each number
>>>> in file1 corresponds to a unique string in column B of file1.
>>>> b) then write a for loop like the following:
>>>> for "person_name" in file2:
>>>>    if "person_name.file2" == "person_name.file1":
>>>>        person_id.file2 == person_id.file1
>>>> c) write into file2 the changes to person_id's...
>>>>
>>>> But it's pretty difficult for me to get past this stage. Am I on the
>>>> right track? And more importantly, how could I learn how to actually
>>>> implement this in smaller stages?
>>>>
>>>>
>>>  You're on the right track, and you're almost there! You've already
>>> broken down the problem into steps. You should now try to implement a
>>> function for each step, and finally you should glue these functions
>>> together into a final program.
>>>
>>> a) Though you don't *have* to use it, csv.reader is really quite simple,
>>> I'd recommend it. Try and write a function that takes a file name as
>>> argument and returns a dictionary of the form { name: id, name: id } (i.e.
>>> the names are the keys).
>>>
>>> b) For this step, you first need a list of all names in file 2. You
>>> could use csv.reader again or you could just parse it. Then, you use the
>>> dictionary to look up the corresponding id. The end goal for this function
>>> is to return a list of lists that looks much like the file you want to end
>>> up with:
>>>
>>> [[id, name],
>>>  [id, name],
>>>  [id, name]]
>>>
>>> c) this step should now be easy. I'd again, recommend csv.writer, it
>>> makes the process pretty simple. You just pass in the nested list from step
>>> (b) and you're pretty much done.
>>>
>>> For tips on the csv module, the list of examples is pretty helpful:
>>> http://docs.python.org/py3k/library/csv.html#examples
>>>  If you need help constructing the lists and dictionaries, my tips would
>>> be 1) think one row at a time, 2) the for loop is your best friend, and 3)
>>> nested lists usually means nested loops
>>>
>>> HTH,
>>> Hugo
>>>
>>
>>
>
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