[Python-Dev] Add a frozendict builtin type (original) (raw)

Victor Stinner victor.stinner at gmail.com
Thu Mar 1 14:07:10 CET 2012

Here are my real-world use cases. Not for security, but for safety and performance reasons (I've built by own RODict and ROList modeled after dictproxy):

- Global, but immutable containers, e.g. as class members

I attached type_final.patch to the issue #14162 to demonstrate how frozendict can be used to implement a "read-only" type. Last version: http://bugs.python.org/file24696/type_final.patch

Example:

class FinalizedType: ... final=True ... attr = 10 ... def hello(self): ... print("hello") ... FinalizedType.attr=12 TypeError: 'frozendict' object does not support item assignment FinalizedType.hello=print TypeError: 'frozendict' object does not support item assignment

(instance do still have a mutable dict)

My patch checks for the final class attribute, but the conversion from dict to frozendict may be done by a function or a type method. Creating a read-only type is a different issue, it's just another example of frozendict usage.

Victor

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