Meaning of expression = expression_sum = expression = df[str(self.expression)] ?

[yohplala]

Hi @maartenbreddels
I am sorry, this is a pure python question.
I could find this line of code in AggregatorDescriptorMean.add_tasks(), line 355.
expression = expression_sum = expression = df[str(self.expression)]

Googling chained assignments in Python, I could find this wikipedia ressource explaining:
The assignments are executed left-to-right so that i = arr[i] = f() evaluates the expression f(), then assigns the result to the leftmost target i, and then assigns the same result to the next target arr[i], using the new value of i. This is essentially equivalent to tmp = f(); i = tmp; arr[i] = tmp

Applied to this row in add_task(), it would translate if I am right into:

expression = df[str(self.expression)]
expression_sum = expression
expression = expression

I don't understand why assigning twice the same value to expression. Please, what am I missing?
Thanks for your reply.
Have a good day,
Bests,

[maartenbreddels]

Ah, I've explained this a bit #1848, and it's indeed code, it doesn't do much, except the full rightmost expression is evaluated, and indeed assigned multiple times. If you want to open a PR to clean up that code that would be appreciated.

[yohplala]

Ah, I've explained this a bit #1848, and it's indeed code, it doesn't do much, except the full rightmost expression is evaluated, and indeed assigned multiple times. If you want to open a PR to clean up that code that would be appreciated.

Sorry, I am just seeing your answer in #1834 . Ok, crystal clear. Yes I can clear this of course. Will not do it right now, but will do it this week-end (sorry, I am not on my dev computer at the moment)
Thanks a lot for your feedback!
Bests,