On May 6, 9:34 pm, Artur Siekielski <artur.siekiel...@gmail.com> wrote: > Hello. > I found this strange behaviour of lambdas, closures and list > comprehensions: > > >>> funs = [lambda: x for x in range(5)] > >>> [f() for f in funs] > > [4, 4, 4, 4, 4] > > Of course I was expecting the list [0, 1, 2, 3, 4] as the result. The > 'x' was bound to the final value of 'range(5)' expression for ALL > defined functions. Can you explain this? Is this only counterintuitive > example or an error in CPython?
Try binding the value of x for each of the inner functions: >>> funs = [lambda x=x: x for x in range(5)] >>> [f() for f in funs] [0, 1, 2, 3, 4] Otherwise, the 'x' is just a global value and the lambdas look it up at when the function is invoked. Really, not surprising at all: >>> x = 10 >>> def f(): ... return x ... >>> x = 20 >>> f() 20 Raymond -- http://mail.python.org/mailman/listinfo/python-list
