Python sort a list with external key

Question

I'm trying to sort a list of entries based on the id of the entries.

I tried this code, but it didn't work:

entries.sort(cmp=None, key=Entry.id, reverse=False)

The objects in the list are entries which have an id.

This is the error I get:

TypeError: 'InstrumentedAttribute' object is not callable

Any ideas?

bereal · Accepted Answer · 2012-12-28 15:49:46Z

7

key has to be a function that takes a list entry and returns a value used in comparison.

As alternative to lambda, use operator.attrgetter:

entries.sort(key=attrgetter('id'))

answered Dec 28, 2012 at 15:49

bereal

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1 Comment

XORcist Over a year ago

this is much faster than the lambda solution

Antimony · Accepted Answer · 2012-12-28 15:44:51Z

3

As the error told you, Key needs to be a function, or more accurately, a callable object.

entries.sort(cmp=None, key=(lambda x:x.id), reverse=False)

answered Dec 28, 2012 at 15:44

Antimony

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1 Comment

Lennart Regebro Over a year ago

And you don't need the cmp= parameter. Not reverse either, of course, but it's OK to add the default for clarity. But in the case of cmp= no clarity is added.

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