I have input consisting of a list of nested lists like this:
l = [[[[[39]]]], [1, 2, 3], [4, [5, 3], 1], [[[[8, 9], 10], 11], 12]]
I want to sort this list based on the sum of all the numbers in the nested lists... so, the values I want to sort by of l would look like this:
[39, 6, 13, 50]
Then I want to sort based on these. So the output should be:
[[1, 2, 3], [4, [5, 3], 1], [[[[39]]]], [[[[8, 9], 10], 11], 12]]
What's a nice pythonic way of doing this?
Python List sort() Method Syntax. The Python sort() method sorts the elements of a list in a given order, including ascending or descending orders. The method works in place, meaning that the changed list does not need to be reassigned in order to modify the list.
Approach : Zip the two lists. Create a new, sorted list based on the zip using sorted(). Using a list comprehension extract the first elements of each pair from the sorted, zipped list.
sort , sorted accept optional key parameter. key function is used to generate comparison key. >>> sorted(lst, key=lambda x: x[1], reverse=True) [['I', 219], ['A', 22], ['P', 14], ['V', 13], ['G', 10], ...] >>>
A slight simplification and generalization to the answers provided so far, using a recent addition to python's syntax:
>>> l = [[[[[39]]]], [1, 2, 3], [4, [5, 3], 1], [[[[8, 9], 10], 11], 12]]
>>> def asum(t): return sum(map(asum, t)) if hasattr(t, '__iter__') else t
...
>>> sorted(l, key=asum)
[[1, 2, 3], [4, [5, 3], 1], [[[[39]]]], [[[[8, 9], 10], 11], 12]]
A little recursive function would do it:
def asum(a):
if isinstance(a, list):
return sum(asum(x) for x in a)
else:
return a
l = [[[[[39]]]], [1, 2, 3], [4, [5, 3], 1], [[[[8, 9], 10], 11], 12]]
l.sort(key=asum)
print l
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