如何在Python中将字典设为只读

问题描述

我有一个像这样的课程:

I have a class like:

class A:
    def __init__(self):
        self.data = {}

，有时我想禁止修改 self.data 字段.

and at some moment I want to prohibit self.data fields modification.

我已阅读 PEP-416拒绝通知，其中有一个有很多方法可以做到这一点.所以我想找到它们.

I've read in PEP-416 rejection notice that there are a lot of ways to do it. So I'd like to find what they are.

我尝试过:

a = A()
a.data = types.MappingProxyType(a.data)

应该可以，但是首先，它是python3.3 +，其次，当我多次执行此禁止"操作时，我得到了这个信息:

That should work but first, its python3.3+ and second, when I do this "prohibition" multiple times I get this:

>>> a.data = types.MappingProxyType(a.data)
>>> a.data = types.MappingProxyType(a.data)
>>> a.data
mappingproxy(mappingproxy({}))

尽管最好多次获得 mappingproxy({})会更好，因为我要禁止"很多次.检查 isinstance(MappingProxyType)是一个选项，但是我认为可以存在其他选项.

though it would be much better to get just mappingproxy({}) as I am going to "prohibit" a lot of times. Check of isinstance(MappingProxyType) is an option, but I think that other options can exist.

谢谢

推荐答案

使用 collections.Mapping 例如

import collections

class DictWrapper(collections.Mapping):

    def __init__(self, data):
        self._data = data

    def __getitem__(self, key):
        return self._data[key]

    def __len__(self):
        return len(self._data)

    def __iter__(self):
        return iter(self._data)

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