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#1
December 5th, 2004, 06:45 PM
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simple list manipulation
i have a nested tuple/list such
a=[(1,2,3,4,5,6),(1,2,5,3,5,3),(2,4,5,3,4,3)] i want to create out of it another list with the elements of the second column for example : b=[2,2,4] . Do you have any idea ? i can just print such result but not as a new list Nikos
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#2
December 5th, 2004, 07:07 PM
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List comprehensions to the rescue!
Code:
>>> a=[(1,2,3,4,5,6),(1,2,5,3,5,3),(2,4,5,3,4,3)] >>> [x[1] for x in a] [2, 2, 4] There are other ways of doing it, but this is by far the simplest. In Python 2.4 you can also use a generator expression to create a generator that will retrieve the results when needed. For a large list this can be much more efficient: Code:
>>> gen = (x[1] for x in a) >>> gen.next() 2 >>> gen.next() 2 >>> gen.next() 4 >>> gen.next() Traceback (most recent call last): File "<stdin>", line 1, in ? StopIteration >>> Dave - The Developers' Coach Last edited by DevCoach : December 5th, 2004 at 07:13 PM.
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