[Python-Dev] chained assignment weirdity

Thu Nov 8 19:06:15 CET 2012

On 08.11.12 03:11, Ned Batchelder wrote:
> Sorry, I should have been clearer: I was asking about weird not to say, 
> "This is weird and should be changed!", but to get clarification from 
> Serhiy about his statement, " It will be weird if a dict comprehension 
> and a plain loop will be inconsistent." I honestly didn't know which 
> behavior he considered inconsistent and therefore weird.

I was referring to two of the most popular idioms to dynamically create a dict.
 d = {}
 for x in a:
 d[k(x)] = v(x)
 d = {k(x): v(x) for x in a}
For now these methods are consistent.
I agree that the use of the side effects here is not a sensible idea, but when such effects occur by accident, it will cause a surprise.