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My script shows one use for class methods, i.e. to map Relational tables and rows to objects in python. class methods come in handy when you want all objects in a class to share one method, in this case to retrieve rows from a table.

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import psycopg
from config import DSN

conn = psycopg.connect(DSN)
cursor = conn.cursor()


class Animal:
    def __init__(self, id, name, breed):
        self.id = id
        self.name = name
        self.breed = breed

class Animals:
    def loadList(cls):
        cursor.execute('select * from animal')
        rows = cursor.fetchall()
        return [Animal(row[0], row[1], row[2]) for row in rows]

    classmethod(loadList)

animals = Animals()
print animals.loadList()

The above uses postgresql as the database, but any database with a python binding can be used.

The schema for the table above is simple:

create table animal ( id integer UNIQUE, name text, breed text);

There are only two rows for this test:

select * from animal; id | name | breed ----+------+------- 1 | sam | cat 2 | mon | cat (2 rows)

1 comment

W.J. van der Laan 19 years ago  # | flag

Uhm.. What is the point of using a class method instead of a normal instance method here?

You call the method loadList on the instance Animals() and not on the class Animals. Furthermore you don't use the cls passed to loadList.

Created by Sameer Chow on Thu, 16 Oct 2003 (PSF)
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