python笔记：pickle、cPickle模块

pickle包

1) 将内存中的对象转换成为文本流：

import pickle# define classclass Contact(object):    def __init__(self, uid, name, age):

self.uid = uid

self.age = age

self.name = name

c = Contact(1001,'aaa',25)

ps = pickle.dumps(c)  #转换成字符串

c_copy = pickle.loads(ps) #转换成对象

使用pickle.dumps()方法可以将对象c转换成了字符串 

当然，我们也可以使用pickle.dump()的方法，将上面两部合二为一:

import pickle

class Contact(object):    def __init__(self, uid, name, age):
self.uid = uid
self.age = age
self.name = name
c = Contact(1005)with open('./tmp.data', 'w') as f:          
    ps = pickle.dump(summer, f)

对象c存储在文件ymp.data

 

2) 重建对象

首先，我们要从文本中读出文本，存储到字符串 (文本文件的输入输出)。然后使用pickle.loads(str)的方法，将字符串转换成为对象。要记得，此时我们的程序中必须已经有了该对象的类定义。

 

此外，我们也可以使用pickle.load()的方法，将上面步骤合并:

import pickle
class Contact(object):    def __init__(self, uid, name, age):
self.uid = uid
self.age = age
self.name = name
fn     = './tmp.data'with open(fn, 'r') as f:    summer = pickle.load(f)

 

 

cPickle包

cPickle包的功能和用法与pickle包几乎完全相同 (其存在差别的地方实际上很少用到)，不同在于cPickle是基于c语言编写的，速度是pickle包的1000倍。对于上面的例子，如果想使用cPickle包，我们都可以将import语句改为:

import cPickle as pickle

就不需要再做任何改动了。

下面时存储数据的小实例：

contact.py

#!/usr/bin/env python#-*- coding:utf-8 -*-import copyimport jsonimport base__all__ = ['Contact']class Contact(base.Base):    '''联系人'''    DEBUG = True    def __init__(self, **kwargs):        self.init(**kwargs)    def init(self, **kwargs):        self.uid = kwargs.pop('uid', 0)        self.name = kwargs.pop('name', '')         self.age = kwargs.pop('age', 0)        self.addr = kwargs.pop('addr','')        self.phone = kwargs.pop('phone', '')         self.ext = json.loads(kwargs.pop('ext', '{}'))    def __str__(self):        return "id:%s,uid:%s,name:%s,age:%s,%s"%(id(self), self.uid,self.name, self.age,','.join(['%s:%s'%(k,v) for k, v in self.ext.iteritems()]))    def __getattr__(self, k):         if Contact.DEBUG:            print 'in Contact __getattr__ %s'%k        return self.ext.get(k)    def get_key(self):        return self.uid    def changed(self):        if getattr(self, 'manager'):            self.manager.changed = True    def set_age(self, age):        assert type(age)==int, 'age must be interge'        self.age = age         self.changed() def set_uid(self, uid):        assert type(uid)==int, 'uid must be interge'        self.uid = uid        self.changed()    def set_name(self, name):        assert type(name)==str, 'name must be string'        self.name = name        self.changed()    def load(self, **kwargs):        return self.init(**kwargs)    def save(self):        m = self.__dict__.pop('manager', None)        data = copy.deepcopy(self.__dict__)        self.manager = m        data['ext'] = json.dumps(data['ext'])        return data

loader.py

#!/usr/bin/env python#-*- coding:utf-8 -*-import osimport sys import cPickleclass Loader(object):    '''cPickle loader'''    def __init__(self, filename=None):        self.filename = filename    def load(self, filename=None):        data = []        filename = filename or self.filename        try:            with open(filename or self.filename, 'r') as fd:                 data = cPickle.load(fd)        except:            print 'load data failed'        return data    def save(self, data, filename=None):        assert (filename or self.filename), 'give a filename to save data'        try:            with open(filename or self.filename, 'w') as fd:                 cPickle.dump(data, fd)         except:            return False        return True

manager.py

#!/usr/bin/env python#-*- coding:utf-8 -*-class Manager(object):    '''联系人管理类'''    def __init__(self, memclass, loader, condition=None):        ''''''        self.changed = False        self.loader = loader        self.memclass = memclass        self.member = self.loader.load(condition) if condition else {}    def add_mem(self, memobj):        okey = memobj.get_key()        if okey in self.member:            return False        memobj.manager = self

<span style="white-space:pre"></span>self.changed = True        self.member[okey] = memobj        return True    def del_mem(self, memobj=None, mkey=None):        obj = None        if memobj:            obj = self.member.pop(memobj.get_key(), None)        if mkey:            obj = self.member.pop(mkey, None)        if obj:

            <span style="font-family: 'courier new', courier; font-size: 13.3333330154419px;">obj.manager = None</span>

        return obj     def find_mem(self, mkey):        return self.member.get(mkey, None)    def load(self, condition=None):        assert not self.changed, "the member is not null, you should save first"        data = self.loader.load(condition)        for e in data:            if isinstance(e, self.memclass):                memobj = e             else:                memobj = self.memclass(**e)            memobj.manager = self            self.member[memobj.get_key()] = memobj    def save(self):        if self.changed:            data = []            for _, memobj in self.member.iteritems():                data.append(memobj.save())            self.loader.save(data)        self.changed = False    def display(self):        for _, m in self.member.iteritems():            print m

main.py

#!/usr/bin/env python#-*- coding:utf-8 -*-import contactimport loaderimport managerdef main():    tmp_loader = loader.Loader('./tmp.data')    tmp_manager = manager.Manager(contact.Contact, tmp_loader)    tmp_contact = contact.Contact()    tmp_contact.set_uid(1001)    tmp_contact.set_age(25)    tmp_contact.set_name('nnn')    tmp_manager.add_mem(tmp_contact)    tmp_manager.save()if __name__=='__main__':    main()