What's wrong with this bit of python code using lambda?

Question

Some python code that keeps throwing up an invalid syntax error:

stat.sort(lambda x1, y1: 1 if x1.created_at < y1.created_at else -1)

Can you revert it to the original, wrong version? Otherwise it is confusing. — Otto Allmendinger
– Otto Allmendinger, Commented Jul 28, 2009 at 18:31
You should accept one of the answers that were useful ;) ;) ;) — Roberto Bonvallet
– Roberto Bonvallet, Commented Jul 29, 2009 at 4:06

Roberto Bonvallet · Accepted Answer · 2009-07-28 15:13:57Z

8

This is a better solution:

stat.sort(key=lambda x: x.created_at, reverse=True)

Or, to avoid the lambda altogether:

from operator import attrgetter
stat.sort(key=attrgetter('created_at'), reverse=True)

answered Jul 28, 2009 at 15:06

Roberto Bonvallet

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3 Comments

+1, that's more readable than my answer, and apparently faster: docs.python.org/library/stdtypes.html#typesseq-mutable.

Just added reverse=True to match the original requirement.

operator.attrgetter() is definitely an improvement, pythonically speaking.

kgiannakakis · Accepted Answer · 2009-07-28 14:42:57Z

1

lambda x1, y1: x1.created_at < y1.created_at and 1 or -1

answered Jul 28, 2009 at 14:42

kgiannakakis

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The and-or hack is ugly and not necessary anymore. Conditional expressions were introduced precisely to avoid it.