Trying to find the array with the largest first element?

max() will automatically start with the first element of the arrays when comparing. All you need to do is:

a = [[4.556, 20, 15], [4.772, 7, 4], [6.88, 5, 2], [2.33, 68, 9]]
max(a)
# [6.88, 5, 2]

If the first elements are equal, it will compare the second, etc.. This process of comparison is described in the data structure docs.

Use the key parameter of max:

from operator import itemgetter
a = [[4.556, 20, 15], [4.772, 7, 4], [6.88, 5, 2], [2.33, 68, 9]]
result = max(a, key=itemgetter(0))
print(result)

Output

[6.88, 5, 2]

The operator.itemgetter function just fetches the first position of the list, for example:

itemgetter(0)([1, 2, 3])

returns 1.

Based on @DaniMesejo's answer.

You can use lambda to save an import

max(a, key=lambda x: x[0])