How to find the list in a list of lists whose sum of elements is the greatest?

Question

I have a list of lists: ``` x = [[1,2,3], [4,5,6], [7,8,9], [2,2,0]] ``` I want to get the list whose sum of its elements is the greatest in the list. In this case `[7,8,9]`. I'd rather have a fancy `map` or `lambda` or list comprehension method than a `for/while/if` loop. Best Regards

Accepted Answer

`max` takes a key argument, with it you can tell max how to calculate the value for each item in an iterable. `sum` will do nicely here:

```
max(x, key=sum)
```

Demo:

```
>>> x = [[1,2,3], [4,5,6], [7,8,9], [2,2,0]]
>>> max(x, key=sum)
[7, 8, 9]
```

If you need to use a different method of summing your items, you can specify your own functions too; this is not limited to the python built-in functions:

```
>>> def mymaxfunction(item):
...     return sum(map(int, item))
...
>>> max([['1', '2', '3'], ['7', '8', '9']], key=mymaxfunction)
['7', '8', '9']
```

How to find the list in a list of lists whose sum of elements is the greatest?

Solution

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