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Sorting a list of bodies by x-coordinate

Asked by Christopher Stanbridge

At one point in my code, I need to sort a list of bodies from least to greatest x-coordinate. I have attempted to use the sorted() method but am not quite sure what I would use as my "key". I know State.pos[0] stores the x-coordinate, but when I try to use
key=State.pos[0]
(or, it seems, any variant thereof) I get the following error.
TypeError: 'property' object has no attribute '__getitem__'

What would the correct sort key be here, or if there is none, what alternate methods would there be to sort particles in order of x-coordinate?

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Jan Stránský
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Best Jan Stránský (honzik) said : 		#1

Hi Christopher,

"key" should be a function to be used for the sort. One possibility is to
use lambda structure [1]

key=lambda b: b.state.pos[0]

cheers
Jan

[1] https://wiki.python.org/moin/HowTo/Sorting
Dne 15.9.2014 21:08 "Christopher Stanbridge" <
<email address hidden>> napsal(a):

> New question #254558 on Yade:
> https://answers.launchpad.net/yade/+question/254558
>
> At one point in my code, I need to sort a list of bodies from least to
> greatest x-coordinate. I have attempted to use the sorted() method but am
> not quite sure what I would use as my "key". I know State.pos[0] store the
> x-coordinate, but when I try to use
> key=State.pos[0]
> (or, it seems, any variant thereof) I get the following error.
> TypeError: 'property' object has no attribute '__getitem__'
>
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Revision history for this message
Christopher Stanbridge (cws105) said : 		#2

Yes, using "lambda b" indeed worked for me. Thank you kindly.

Revision history for this message
Christopher Stanbridge (cws105) said : 		#3

Thanks Jan Stránský, that solved my question.