Brendan wrote:
> Hi all
>
> I'm new to Python (and programming in general), and I can't decide what
> is the most 'pythonic' way to approach a problem. Your advice would be
> appreciated.
>
> I have a bunch of 'scans', containing the data measured from one of
> several types of 'model'. Each 'model' has different values for a list
> of constants I want to create 'analyses' which interpret the data from
> the scans, with reference the appropriate model. So far, I have come
> up with three strategies to store this information, illustrated below
> (I've simplified the constant list to just two):
>
> 1) Store the model constants as class instances:
>
> class Model:
> def __init__(self, numBumps, sizeOfBumps):
> self.__dict__.update(locals()); del self.self
>
> MODEL1 = Model(1, 2)
> MODEL2 = Model(3, 4)
> #etc
My vote would go with this one, as it is the closest to
a C-style struct or a Pascal record. If you have to
change the field list, you only need to change it in
one place, the class.
> 2) Store the model constants as class variables:
>
> class MODEL1:
> numBumps = 1
> sizeOfBumps = 2
>
> class MODEL2:
> numBumps = 3
> sizeOfBumps = 4
Duplicated data... yuck. Same with method 3.
> There may be more options, but at this point I became paralyzed with
> choice. I worry about getting stuck with an unworkable structure since
> I don't have the experience to decide the merits of each in advance. I
> get way too frustrated about these things :)
:-)
If all the constants have the same field structure,
stick with method 1.
In a later post, you wrote:
> The reason I'm using that method for assigning
> instance attributes is that the argument list for
> __init__ is LOOONG. (There are many constants, I
only > gave two for the examples). I wanted to avoid
typing > them out twice.
You could always copy-and-paste...
How many is LOOONG? Ten? Twenty? One hundred?
If it is closer to 100 than to 10, I would suggest
putting your constants into something like an INI file:
[MODEL1] # or something more meaningful
numBumps: 1
sizeOfBumps: 99
[MODEL2]
numBumps: 57
sizeOfBumps: 245
etc.
Then sub-class the ConfigParser to create struct-like
objects from an ini file. Something vaguely like:
# warning: pseudo-code, seriously not tested!!!
class Config2Consts(ConfigParser):
"""Reads an INI file, and creates a struct-like
object from each section, storing that object
in the local scope with the name of the section.
"""
class Struct:
def __init__(self):
pass
def make_single_constant_object(self, sectionname):
obj = Struct()
for field in INI_FILE[sectionname]:
obj.__dict__[field.name] = field.value
locals().update({sectionname: obj})
If you are likely to be changing the constants (either
names, field names, or values) an hour or three
developing this code will save you a lot of heart-ache
later.
--
Steven.
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