Python 在 2 元素列表中查找最大值

Question

I have a 2 elements list like this one:

[(0, 0.020449258), (1, 0.020540833), (2, 0.35077244), (3, 0.5467364), (4, 0.020515079), (5, 0.020485992), (6, 0.020499969)]

My goal is to fix the max value in the second column and return the first one. So as per example I should be able to return 3 as it got the max value (0.5467364)

I'm able to find the max value using this code (where "result" is the list above):

max_value = max(l[1] for l in result)

I'm struggling to get the index of such element to return the value =>3, I tryed:

max_index = result.index(max_value)

and is returning this error:

ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

Thx

Answer 1

Can you try the following:

arr = [
    (0, 0.020449258), 
    (1, 0.020540833), 
    (2, 0.35077244), 
    (3, 0.5467364), 
    (4, 0.020515079), 
    (5, 0.020485992), 
    (6, 0.020499969)
]
# sort the array based on the second element
arr = sorted(arr, key=lambda x: x[1], reverse=True)
# get the first element of the sorted array
print(arr[0][0])

Output

3

Answer 2

A simple answer could be:

list = [(0, 0.020449258), (1, 0.020540833), (2, 0.35077244), (3, 0.5467364), (4, 0.020515079), (5, 0.020485992), (6, 0.020499969)]
max_index = 0
max_value = list[0][1]
for index in range(1, len(list)):
    if list[index][1] > max_value:
        max_value = list[index][1]
        max_index = index
print(max_index, max_value)

Answer 3

Complexity O(n)

a = [(0, 0.020449258), (1, 0.020540833), (2, 0.35077244), (3, 0.5467364), (4, 0.020515079), (5, 0.020485992), (6, 0.020499969)]

value = (0, 0)
    for i in a:
        if i[1] > value[1]:
            value = i
print(value) --> (3, 0.5467364)
# or print value[0]

Answer 4

You could use list comprehension and numpy.argmax to break it down to 4 lines as follows:

list = [(0, 0.020449258), (1, 0.020540833), (2, 0.35077244), (3, 0.5467364), (4, 0.020515079), (5, 0.020485992), (6, 0.020499969)]

list.sort()   # The tuples are now sorted accordingly

values_list = [i[1] for i in list]               # List of the second elements
max_index = numpy.argmax(values_list)            # Index of max tuple
max_first_element = list[max_index][0]           # First element in that max tuple

print(max_first_element)

Please dont forget to import numpy at the top!