filtering elements from list of lists in Python?

Question

I want to filter elements from a list of lists, and iterate over the elements of each element using a lambda. For example, given the list:

a = [[1,2,3],[4,5         


        

Answer 1

You can explicitly name the sublist elements (assuming there's always a fixed number of them), by giving lambda a tuple as its argument:

>>> a = [[1,2,3],[4,5,6]]
>>> N = 10
>>> filter(lambda (i, j, k): i + j + k > N, a)
[[4, 5, 6]]

If you specify "lambda i, j, k" as you tried to do, you're saying lambda will receive three arguments. But filter will give lambda each element of a, that is, one sublist at a time (thus the error you got). By enclosing the arguments to lambda in parenthesis, you're saying that lambda will receive one argument, but you're also naming each of its components.