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From: Marko Rauhamaa <marko@pacujo.net>
Newsgroups: comp.lang.python
Subject: Re: What does a list comprehension do
Date: Thu, 26 Nov 2015 15:56:41 +0200
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Antoon Pardon <antoon.pardon@rece.vub.ac.be>:

> I don't understand. What I propose would be a minor change in
> how list comprehension works. I don't see how your example
> can be turned into a list comprehension.

The list comprehension is only a special case of the interaction between
closures and variables. If you dabble with list comprehensions and
lambdas, you'll need to make consistent changes in closure semantics.

That would lead to the trouble I mentioned. Closures need to have
dynamic access to the variables they refer to.

This whole issue is a consequence of Python's assignment semantics. If
Python didn't allow altering the values of variables, we wouldn't be
having this discussion.

BTW, all(!?) other languages from Java to Scheme share closure semantics
with Python so you would really be making a mess by changing Python.


Marko