python-patterns/factory_method.py

#encoding=utf-8
'''http://ginstrom.com/scribbles/2007/10/08/design-patterns-python-style/'''

class GreekGetter:
    """A simple localizer a la gettext"""
    def __init__(self):
        self.trans = dict(dog="σκύλος", cat="γάτα")

    def get(self, msgid):
        """We'll punt if we don't have a translation"""          
        try:
            return self.trans[msgid]
        except KeyError:
            return str(msgid)

class EnglishGetter:
    """Simply echoes the msg ids"""     
    def get(self, msgid):
        return str(msgid)

def get_localizer(language="English"):
    """The factory method"""
    languages = dict(English=EnglishGetter, Greek=GreekGetter)
    return languages[language]()

# Create our localizers
e, g = get_localizer("English"), get_localizer("Greek")
# Localize some text
for msgid in "dog parrot cat bear".split():
    print(e.get(msgid), g.get(msgid))