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Dear all,

I'm a newbie in python and would be acknowledge if somebody could shed
some light on associative arrays.
More precisely, I would like to create a multi-dimensional associative
array. I have for example a list of students which are identified
uniquely by their student IDs. Additionally, for each student I have
some information: FirstName, LastName, etc.

The array would have then the following form:
[StudentID] => [FirstName][LastName][Telephone]...[ ... ]

I would like to be able to access a field directly by using a
StudentID
[StudentID][FirstName]
[StudentID][LastName]

How could I manipulate such an array (create the array, add elements,
access data)?

Best wishes

On Wed, Mar 31, 2010 at 10:10 PM, Javier Montoya <> wrote:
> Dear all,
>
> I'm a newbie in python and would be acknowledge if somebody could shed
> some light on associative arrays.
> More precisely, I would like to create a multi-dimensional associative
> array. I have for example a list of students which are identified
> uniquely by their student IDs. Additionally, for each student I have
> some information: FirstName, LastName, etc.
>
> The array would have then the following form:
> [StudentID] => [FirstName][LastName][Telephone]...[ ... ]
>
> I would like to be able to access a field directly by using a
> StudentID
> [StudentID][FirstName]
> [StudentID][LastName]
>
> How could I manipulate such an array (create the array, add elements,
> access data)?
>

Did you try the python tutorial? Dictionaries might be what you are
looking for.

http://docs.python.org/tutorial/data...l#dictionaries

--
regards,
kushal

Javier Montoya wrote:
> Dear all,
>
> I'm a newbie in python and would be acknowledge if somebody could shed
> some light on associative arrays.
> More precisely, I would like to create a multi-dimensional associative
> array. I have for example a list of students which are identified
> uniquely by their student IDs. Additionally, for each student I have
> some information: FirstName, LastName, etc.
>
> The array would have then the following form:
> [StudentID] => [FirstName][LastName][Telephone]...[ ... ]
>
> I would like to be able to access a field directly by using a
> StudentID
> [StudentID][FirstName]
> [StudentID][LastName]
>
> How could I manipulate such an array (create the array, add elements,
> access data)?
>
> Best wishes
>
>
>
Create a class for student with attributes for ID, FirstName, LastName, etc.

class Student:
def __init__(self, id, FirstName, ...):
self.id = id
self.FirstName = FirstName
...

then whenever you create a student object, use a dictionary to associate
the object with its is
AA = {} # An empty dictionary
s = Student(...)
AA[s.id] = s
... and repeat for many students...

Then to access a student's object given an id:
s = AA[id]
print s.id, s.FirstName, s.LastName, ...


I'd *not* call this a multi-dimension association, but rather just an
association between student objects and their ids.

Hope that helps,

Gary Herron

--
Gary Herron, PhD.
Department of Computer Science
DigiPen Institute of Technology
(425) 895-4418

On Mar 31, 7:36*pm, Gary Herron <gher...@digipen.edu> wrote:
> JavierMontoyawrote:
> > Dear all,
>
> > I'm a newbie in python and would be acknowledge if somebody could shed
> > some light on associative arrays.
> > More precisely, I would like to create a multi-dimensional associative
> > array. I have for example a list of students which are identified
> > uniquely by their student IDs. Additionally, for each student I have
> > some information: FirstName, LastName, etc.
>
> > The array would have then the following form:
> > [StudentID] => [FirstName][LastName][Telephone]...[ ... ]
>
> > I would like to be able to access a field directly by using a
> > StudentID
> > [StudentID][FirstName]
> > [StudentID][LastName]
>
> > How could I manipulate such an array (create the array, add elements,
> > access data)?
>
> > Best wishes
>
> Create a class for student with attributes for ID, FirstName, LastName, etc.
>
> * class Student:
> * * * def __init__(self, id, FirstName, ...):
> * * * * * self.id = id
> * * * * * self.FirstName = FirstName
> * * * * * ...
>
> then whenever you create a student object, use a dictionary to associate
> the object with its is
> * AA = {} # An empty dictionary
> * s = Student(...)
> * AA[s.id] = s
> * ... and repeat for many students...
>
> Then to access a student's object given an id:
> * s = AA[id]
> * print s.id, s.FirstName, s.LastName, ...
>
> I'd *not* call this a multi-dimension association, but rather just an
> association between student objects and their ids.
>
> Hope that helps,
>
> Gary Herron
>
> --
> Gary Herron, PhD.
> Department of Computer Science
> DigiPen Institute of Technology
> (425) 895-4418

Dear all,

Thanks for your suggestions, it worked! As Gary suggested, I created a
'student' class and mapped its objects to a dictionary.
Is it possible to sort the dictionary by the student's grades in
descending order?

Best wishes

On Thu, Apr 1, 2010 at 3:58 AM, Javier Montoya <> wrote:
> On Mar 31, 7:36Â*pm, Gary Herron <gher...@digipen.edu> wrote:
>> JavierMontoyawrote:
>> > Dear all,
>>
>> > I'm a newbie in python and would be acknowledge if somebody could shed
>> > some light on associative arrays.
>> > More precisely, I would like to create a multi-dimensional associative
>> > array. I have for example a list of students which are identified
>> > uniquely by their student IDs. Additionally, for each student I have
>> > some information: FirstName, LastName, etc.
>>
>> > The array would have then the following form:
>> > [StudentID] => [FirstName][LastName][Telephone]...[ ... ]
>>
>> > I would like to be able to access a field directly by using a
>> > StudentID
>> > [StudentID][FirstName]
>> > [StudentID][LastName]
>>
>> > How could I manipulate such an array (create the array, add elements,
>> > access data)?
>>
>> > Best wishes
>>
>> Create a class for student with attributes for ID, FirstName, LastName, etc.
>>
>> Â* class Student:
>> Â* Â* Â* def __init__(self, id, FirstName, ...):
>> Â* Â* Â* Â* Â* self.id = id
>> Â* Â* Â* Â* Â* self.FirstName = FirstName
>> Â* Â* Â* Â* Â* ...
>>
>> then whenever you create a student object, use a dictionary to associate
>> the object with its is
>> Â* AA = {} # An empty dictionary
>> Â* s = Student(...)
>> Â* AA[s.id] = s
>> Â* ... and repeat for many students...
>>
>> Then to access a student's object given an id:
>> Â* s = AA[id]
>> Â* print s.id, s.FirstName, s.LastName, ...
>>
>> I'd *not* call this a multi-dimension association, but rather just an
>> association between student objects and their ids.
>>
>> Hope that helps,
>>
>> Gary Herron
>>
>> --
>> Gary Herron, PhD.
>> Department of Computer Science
>> DigiPen Institute of Technology
>> (425) 895-4418
>
> Dear all,
>
> Thanks for your suggestions, it worked! As Gary suggested, I created a
> 'student' class and mapped its objects to a dictionary.
> Is it possible to sort the dictionary by the student's grades in
> descending order?

Dictionaries are not ordered collections, so they themselves cannot be sorted.

However, if you want a list of students sorted in the manner you stated:
class_rank = list(garys_dictionary.values())
class_rank.sort(key=lambda student: student.grade, reverse=True)

Cheers,
Chris
--
http://blog.rebertia.com

Javier Montoya wrote:

> Is it possible to sort the dictionary by the student's grades in
> descending order?

You cannot sort dictionaries, but you can put dictionary items into a list
and then sort that.

Assumming that you have a dictionary student_dict that maps student IDs to
Student instances and a function get_grade() to find a student's grade you'd
do

def get_grade(student):
return course[student.student_id].grade # or whatever it takes

students_by_grade = sorted(student_dict.itervalues(), key=get_grade,
reverse=True)

for student in students_by_grade:
print student.first_name, student.last_name

However, problems like the above are normally handled best using a SQL
database, so I recommend that you have a look at

http://docs.python.org/library/sqlite3.html

Peter

On Wed, 31 Mar 2010 09:40:30 -0700, Javier Montoya wrote:

> Dear all,
>
> I'm a newbie in python and would be acknowledge if somebody could shed
> some light on associative arrays.
> More precisely, I would like to create a multi-dimensional associative
> array. I have for example a list of students which are identified
> uniquely by their student IDs. Additionally, for each student I have
> some information: FirstName, LastName, etc.
>
> The array would have then the following form: [StudentID] =>
> [FirstName][LastName][Telephone]...[ ... ]
>
> I would like to be able to access a field directly by using a StudentID
> [StudentID][FirstName]
> [StudentID][LastName]
>
> How could I manipulate such an array (create the array, add elements,
> access data)?
>
> Best wishes

I know this is not a direct answer, but in your case I would probably use
a database, because it is the easiest and most standardized way to access
such types of data. If you don't want something heavyweight, use sqlite
with in-memory databases/persistent file.

Look at sqlite3 module in python.





--
Harishankar (http://harishankar.org http://literaryforums.org)