[Python-Dev] Proposal: defaultdict (original) (raw)

"Martin v. Löwis" martin at v.loewis.de
Sat Feb 18 00:06:20 CET 2006

Ian Bicking wrote:

I know I at least don't like code that mixes up access and modification. Maybe not everyone does (or maybe not everyone thinks of getitem as "access", but that's unlikely). I will assert that it is Pythonic to keep access and modification separate, which is why methods and attributes are different things, and why assignment is not an expression, and why functions with side effects typically return None, or have names that are very explicit about the side effect, with names containing command verbs like "update" or "set". All of these distinguish access from modification.

Do you never write

d[some_key].append(some_value)

This is modification and access, all in a single statement, and all without assignment operator.

I don't see the setting of the default value as a modification. The default value has been there, all the time. It only is incarnated lazily.

Regards, Martin

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