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From: Marko Rauhamaa <marko@pacujo.net>
Newsgroups: comp.lang.python
Subject: Re: Late-binding of function defaults (was Re: What is a function parameter =[] for?)
Date: Thu, 26 Nov 2015 08:52:07 +0200
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Xref: csiph.com comp.lang.python:99532

Steven D'Aprano <steve@pearwood.info>:

> Making tuples mutable would break their use as dictionary keys, which is a
> *critical* use.

No, it wouldn't. Any object that provides __hash__() and __eq__() can be
used as a key.

Nothing prevents using mutable objects as keys in Python.

    Egon Spengler: There's something very important I forgot to tell you.
    Peter Venkman: What?
    Spengler: Don't use mutable keys.
    Venkman: Why?
    Spengler: It would be bad.
    Venkman: I'm fuzzy on the whole good/bad thing. What do you mean,
       "bad"?
    Spengler: Try to imagine all life as you know it stopping
        instantaneously and every molecule in your body exploding at the
        speed of light.
    Ray Stantz: Total protonic reversal!
    Venkman: Right. That's bad. Okay. All right. Important safety tip.
        Thanks, Egon.


Marko