On Thu, 25 Dec 2008 13:22:15 -0500
Matthew Dubins <matt.dub...@sympatico.ca> wrote:
> Hello all,
>
> I have made a python script to upload contact information from an
> excel worksheet to an online database. One part of the program that
> really tripped me up was when I wanted to call specific class methods
> that I had made to deal with specific types of contact information
> (Parent's name, Child's name, Phone #, etc). My first thought was to
> make it easy using the exec statement.
>
> The code (a method within a class) looked like this:
> ----------
> def parse(self, data, data_type)
> exec "self.__parse_%s(data)" % data_type
> ----------
> The data_type variable contains strings that exactly match the
> spellings of the 2nd word in the titles of the class methods that I
> wanted to call for each data_type inputted into the parse function.
> For some reason, *it didn't work*. Alternately, I found the ugly
> code shown below to be functional. As you can see, for each
> data_type, I call the corresponding class method that I've
> specified. Please help me to transform my ugly functional code into
> concise functional code. :)
>
> Thanks,
> Matthew
> ----------
> def parse(self, data, data_type):
> if data_type == 'nocall':
> self.__parse_nocall(data)
> elif data_type == 'DOB':
> self.__parse_DOB(data)
> elif data_type == 'gender':
> self.__parse_gender(data)
> elif data_type == 'Prematurity':
> self.__parse_Prematurity(data)
> elif data_type == 'email':
> self.__parse_email(data)
> elif data_type == 'languages':
> self.__parse_languages(data)
> elif data_type == 'phone':
> self.__parse_phone(data)
> elif data_type == 'cname':
> self.__parse_cname(data)
> elif data_type == 'pname':
> self.__parse_pname(data)
> elif data_type == 'address':
> self.__parse_address(data)
> elif data_type == 'duedate':
> self.__parse_dudedate(data)
>
This is precisely what subclasses were designed for:
class DataField(object):
def __init__(self, data):
self.data = data
def parse(self):
pass
class AddressDataField(DataField):
def parse(self):
self.data = do_something(self.data)
class DueDateDataField(DataField):
def parse(self):
self.data = parse_date(self.data)
and so forth. Then your if/else chain can be pulled out to the place where you
instantiate each field:
if data_type=='address':
field=AddressDataField(data)
elif data_type=='due_date':
field=DueDateDataField(data)
else:
field = DataField(data)
Then a simple field.parse() will do the right thing to field.data(). You might
even include the parsing in __init__(). Define __init__() once on the base
class (DataField), and it will pull the proper parse method from the subclass.
Happy Hacking, and Merry Christmas.
Cliff
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