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+--- Thread: How to redefine object so that all user- objects have the necessary capabilities? (/thread-16173.html)
How to redefine object so that all user- objects have the necessary capabilities? - AlekseyPython - Feb-17-2019
When I used the pickle library, it turned out that it does not save the current values of the class members (after recovery pickle fills them with the original values). Pickle save only current values of instance variables. Therefore, I wrote a class 'AbstractSavingObject', which implements saving, including the current values of class variables. Now I want to give this opportunity to all my classes (for the ability to save in a dump all objects when an exception occurs) and do not want to write inheritance from 'AbstractSavingObject' everywhere.
How to do this?
RE: How to redefine object so that all user- objects have the necessary capabilities? - micseydel - Feb-18-2019
Could you post short code exemplifying what you're talking about?
Also, if you haven't heard already, pickle is typically considered a security hole, so you might want to consider JSON or something else for your serialization. That won't directly help you with saving class variable though, I suspect that's something you'll just have to do manually.
RE: How to redefine object so that all user- objects have the necessary capabilities? - AlekseyPython - Feb-20-2019
Thank you for your interest!
import os, pickle
class A:
b=2
def __init__(self, value):
self.c = value
if not os.path.exists('MyPicl.bin'):
with open('MyPicl.bin', 'wb') as dump:
old_a = A(1)
old_a.__class__.b = 3
print(old_a.b)
print(old_a.__class__.b)
print(old_a.c)
pickler = pickle.Pickler(dump, pickle.HIGHEST_PROTOCOL)
pickler.dump(old_a)
else:
with open('MyPicl.bin', 'rb') as dump:
unpickler = pickle.Unpickler(dump)
new_a = unpickler.load()
print(new_a.b)
print(new_a.__class__.b)
print(new_a.c)If you run this code twice (completely closing the program after the first launch), the first time you get the output:Output:3
3
1Output:2
2
1object.parents.append(MyClassForCorrectSaving)
class A(object):
b=2
def __init__(self, value):
self.c = value
RE: How to redefine object so that all user- objects have the necessary capabilities? - AlekseyPython - Feb-20-2019
(Feb-18-2019, 06:41 PM)micseydel Wrote: Could you post short code exemplifying what you're talking about?
Also, if you haven't heard already, pickle is typically considered a security hole, so you might want to consider JSON or something else for your serialization. That won't directly help you with saving class variable though, I suspect that's something you'll just have to do manually.
json has limitations:
a) tuple during serialization / deserialization transform into a list.
b) what happens with set- it's unknown.
c) dict keys should ONLY have the string / number type.
Therefore, this method does not allow writing arbitrary code.
RE: How to redefine object so that all user- objects have the necessary capabilities? - micseydel - Feb-27-2019
Apologies for taking a while to get back, things have been pleasantly busy.
I've looked a bit and I can't find any direct way to get what you want. If you don't mind sticking to Python literals instead of classes, ast.literal_eval might be worth taking a look at; assuming your objects are simple enough, you can just print them and then evaluate them with literal_eval when you read from a file.
RE: How to redefine object so that all user- objects have the necessary capabilities? - AlekseyPython - Mar-03-2019
My decision:
class MyObject:
def __init__(self):
print('I'm here!')
__builtins__.object = MyObject