保存对象(数据持久化)
我已经创建了一个这样的对象：
company1.name = 'banana'
company1.value = 40我想要保存此对象。我该怎么做呢？
回答 3
Stack Overflow用户
发布于 2014-08-04 20:49:23
我认为假设对象是一个class是一个非常有力的假设。如果它不是class呢？还有一个假设是，对象没有在解释器中定义。如果它是在解释器中定义的呢？另外，如果属性是动态添加的呢？当一些python对象在创建后将属性添加到它们的__dict__中时，pickle不会考虑添加这些属性(即，它“忘记”它们是被添加的--因为pickle通过引用对象定义来序列化)。
在所有这些情况下，pickle和cPickle都会让你大失所望。
如果您希望保存具有属性(在对象定义中添加或之后添加)的object (任意创建的)…最好的选择是使用dill，它可以序列化python中的几乎任何内容。
我们从一个类…开始
Python 2.7.8 (default, Jul 13 2014, 02:29:54)
[GCC 4.2.1 Compatible Apple Clang 4.1 ((tags/Apple/clang-421.11.66))] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import pickle
>>> class Company:
... pass
...
>>> company1 = Company()
>>> company1.name = 'banana'
>>> company1.value = 40
>>> with open('company.pkl', 'wb') as f:
... pickle.dump(company1, f, pickle.HIGHEST_PROTOCOL)
...
>>> 现在关机，然后重启...
Python 2.7.8 (default, Jul 13 2014, 02:29:54)
[GCC 4.2.1 Compatible Apple Clang 4.1 ((tags/Apple/clang-421.11.66))] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import pickle
>>> with open('company.pkl', 'rb') as f:
... company1 = pickle.load(f)
...
Traceback (most recent call last):
File "<stdin>", line 2, in <module>
File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/pickle.py", line 1378, in load
return Unpickler(file).load()
File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/pickle.py", line 858, in load
dispatch[key](self)
File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/pickle.py", line 1090, in load_global
klass = self.find_class(module, name)
File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/pickle.py", line 1126, in find_class
klass = getattr(mod, name)
AttributeError: 'module' object has no attribute 'Company'
>>> Oops…pickle不能处理它。让我们试试dill。为了更好地衡量，我们将抛出另一个对象类型( lambda)。
Python 2.7.8 (default, Jul 13 2014, 02:29:54)
[GCC 4.2.1 Compatible Apple Clang 4.1 ((tags/Apple/clang-421.11.66))] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import dill
>>> class Company:
... pass
...
>>> company1 = Company()
>>> company1.name = 'banana'
>>> company1.value = 40
>>>
>>> company2 = lambda x:x
>>> company2.name = 'rhubarb'
>>> company2.value = 42
>>>
>>> with open('company_dill.pkl', 'wb') as f:
... dill.dump(company1, f)
... dill.dump(company2, f)
...
>>> 现在读出文件。
Python 2.7.8 (default, Jul 13 2014, 02:29:54)
[GCC 4.2.1 Compatible Apple Clang 4.1 ((tags/Apple/clang-421.11.66))] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import dill
>>> with open('company_dill.pkl', 'rb') as f:
... company1 = dill.load(f)
... company2 = dill.load(f)
...
>>> company1
<__main__.Company instance at 0x107909128>
>>> company1.name
'banana'
>>> company1.value
40
>>> company2.name
'rhubarb'
>>> company2.value
42
>>> 它起作用了。pickle失败而dill没有失败的原因是，dill将__main__视为模块(在很大程度上)，而且还可以通过引用来筛选类定义(就像pickle一样)。dill可以lambda的原因是它为它提供了一个名称…然后酸洗魔法就会发生。
实际上，有一种更简单的方法来保存所有这些对象，特别是当你创建了很多对象的时候。只需转储整个python会话，稍后再回来。
Python 2.7.8 (default, Jul 13 2014, 02:29:54)
[GCC 4.2.1 Compatible Apple Clang 4.1 ((tags/Apple/clang-421.11.66))] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import dill
>>> class Company:
... pass
...
>>> company1 = Company()
>>> company1.name = 'banana'
>>> company1.value = 40
>>>
>>> company2 = lambda x:x
>>> company2.name = 'rhubarb'
>>> company2.value = 42
>>>
>>> dill.dump_session('dill.pkl')
>>> 现在关掉你的电脑，去享受一杯浓缩咖啡或者别的什么，然后再回来...
Python 2.7.8 (default, Jul 13 2014, 02:29:54)
[GCC 4.2.1 Compatible Apple Clang 4.1 ((tags/Apple/clang-421.11.66))] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import dill
>>> dill.load_session('dill.pkl')
>>> company1.name
'banana'
>>> company1.value
40
>>> company2.name
'rhubarb'
>>> company2.value
42
>>> company2
<function <lambda> at 0x1065f2938>唯一的主要缺点是dill不是python标准库的一部分。所以如果你不能在你的服务器上安装一个python包，那么你就不能使用它。
但是，如果您能够在系统上安装python包，则可以使用git+https://github.com/uqfoundation/dill.git@master#egg=dill获得最新的dill。您可以使用pip install dill获取最新发布的版本。
Stack Overflow用户
发布于 2019-11-28 11:26:25
在python3中使用您问题中的company1的一个简单示例。
import pickle
# Save the file
pickle.dump(company1, file = open("company1.pickle", "wb"))
# Reload the file
company1_reloaded = pickle.load(open("company1.pickle", "rb"))然而，正如这篇answer所指出的，pickle经常失败。所以你真的应该使用dill。
import dill
# Save the file
dill.dump(company1, file = open("company1.pickle", "wb"))
# Reload the file
company1_reloaded = dill.load(open("company1.pickle", "rb"))Stack Overflow用户
发布于 2021-05-11 15:30:08
较新版本的熊猫也有保存泡菜的功能。
我发现这更容易。例如：
pd.to_pickle(object_to_save,'/temp/saved_pkl.pickle' )https://stackoverflow.com/questions/4529815
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