[Tutor] How do I make a variable that refers to an object have thesame label as the object's name ?

[Alan Gauld]

> when creating a series of objects, where each object represents a 
> field from
> a submitted html form, how do I make variables that reference the 
> objects be
> the same as the names of the respective objects ?

The usual solution for this is to use a dictionary keyed by object 
name.
There is an example of this technique in my OOP topic in my tutor
using bank accounts keyed by account number - under the heading
"Collections of Objects".

There are other solutions based on modifying the global namerspace
but thats messy IMHO and makes your code very dependant on the
pre-knowledge of the fields passed which can introduce maintenance
problems later.


Using a dictionary your code becomes:

> class Datum:
>    def __init__(self, value, required=None, label=None):
>        self.value = value
>        self.required = required
>        self.label = label
>
> and a dictionary of submitted values:
>
> some_dict = {'applicant_full_name':'John Smith',
> 'applicant_address_line_1':'100 Main Street', 
> 'applicant_city':'Anytown',
> 'applicant_state':'WY', 'applicant_postal_code':'55555', 
> 'country':'US', '
> applicant_email':'jsmith at server.gov', 'applicant_telephone':'555 555 
> 5555'}
>
> and I created a list of objects like so:
>
> some_list = {}
> for key, value in some_dict.items():
>    some_list[key] = Datum(value)

> to make it so I can refer to each respective Datum instance by its 
> Datum.key,
> e.g., applicant_full_name would refer to the Datum instance with key
> 'applicant_full_name' and applicant_full_name.value would give me 
> "John
> Smith."  I tried:

print some_list['applicant_full_name'].value

> for x in some_list:
>    some_string = "%s = %s"  % (x.key, x)
>    eval(some_string)

You would need exec() not eval but...
eval and exec both have serious security implications and should
be avoided where possible. Hopefully the dictionary technique achieves 
what you want?


-- 
Alan Gauld
Author of the Learn to Program web site
http://www.freenetpages.co.uk/hp/alan.gauld