10
In IronPython 2.7.1 you have clr.ImportExtensions for this use case.
import clr
clr.AddReference("System.Core")
import System
clr.ImportExtensions(System.Linq)
# will print 3 and 4 :)
[2, 3, 4].Where(lambda x: x != 2).ToList().ForEach(System.Console.WriteLine)
A little background: IronPython ...