Python的设计模式

# _*_ coding=utf-8 _*_


class Event(object):
    _observers = []

    def __init__(self, subject):
        self.subject = subject

    @classmethod
    def register(cls, observer):
        if observer not in cls._observers:
            cls._observers.append(observer)

    @classmethod
    def unregister(cls, observer):
        if observer in cls._observers:
            cls._observers.remove(observer)

    @classmethod
    def notify(cls, subject):
        event = cls(subject)
        for observer in cls._observers:
            observer(event)


class WriteEvent(Event):

    def __repr__(self):
        return 'WriteEvent'


def log(event):
    print '%s was written' % event.subject


WriteEvent.register(log)


class AnotherObserver(object):
    def __call__(self, event):
        print 'Yeah %s told me!' % event


WriteEvent.register(AnotherObserver())
WriteEvent.notify("a given file")

# _*_ coding=utf-8 _*_

class vlist(list):
    def accept(self, visitor):
        visitor.visit_list(self)


class vdict(dict):
    def accept(self, visitor):
        visitor.visit_dict(self)


class Printer(object):
    def visit_list(self, ob):
        print 'list cintent'
        print str(ob)

    def visit_dict(self, ob):
        print 'dict keys: %s' % ','.join(ob.keys())


# a_list = vlist([1, 2, 5])
# a_list.accept(Printer())
# a_dict = vdict({'one': 1, 'two': 2, 'three': 3})
# a_dict.accept(Printer())


# def visit(visited, visitor):
#     cls = visited.__class__.__name__
#     meth = 'visit_%s' % cls
#     method = getattr(visitor, meth, None)
#     if method is not None:
#         method(visited)
#
# visit([1, 2, 5], Printer())
# visit({'one': 1, 'two': 2, 'three': 3}, Printer())
import os


def visit(directory, visitor):
    for root, dirs, files in os.walk(directory):
        for file in files:
            ext = os.path.splitext(file)[-1][1:]
            if hasattr(visitor, ext):
                getattr(visitor, ext)(file)

class FileReader(object):
    def pdf(self, file):
        print 'processing %s' % file

walker = visit("/Users/lucas/Downloads", FileReader())

# _*_ coding=utf-8 _*_
from itertools import groupby


class Indexer(object):

    def process(self, text):
        text = self._normalize_text(text)
        words = self._split_text(text)
        words = self._remove_stop_words(words)
        stemmed_words = self._stem_words(words)
        return self._frequency(stemmed_words)

    def _normalize_text(self, text):
        return text.lower().strip()

    def _split_text(self, text):
        return text.split()

    def _remove_stop_words(self, words):
        raise NotImplementedError

    def _stem_words(self, words):
        raise NotImplementedError

    def _frequency(self, words):
        counts = {}
        for word in words:
            counts[words] = counts.get(word, 0) + 1
        return counts

class BasicIndexer(Indexer):

    _stop_words = ('he', 'she', 'is', 'and', 'or')

    def _remove_stop_words(self, words):
        return [word for word in words if word not in self._stop_words]

    def _stem_words(self, words):
        return [(len(word) > 2 and word.rstrip('aeiouy')
                 or word) for word in words]

    def _frequency(self, words):
        freq = {}
        for word in words:
            freq[word] = freq.get(word, 0) + 1
        return freq

indexer = BasicIndexer()
print indexer.process(('My Tailor is rich and he is also my friend'))