Python，我怎样才能找到这些元素的总和？

Question

Find the sum of n elements of the following row of numbers:
1, -0.5, 0.25, -0.125...
The number of elements (n) is entered from the keyboard.

Answer 1

This will work:

row = "1, -0.5, 0.25, -0.125, 0.5, -0.14, 0.2, -0.34"
n = int(input())
nth_sum = sum(map(float, row.split(",")[:n]))

Answer 2

You're looking for something like this?

l = []
for i in range(int(input())):
    if i%2 ==0:
        l.append(1/2**i)
    else:
        l.append(-(1/2**i))
print(sum(l))

Answer 3

You can use the formula for the sum of a geometric series:

n = int(input('number: '))
result = -2 * (1 + 1/2 ** n ) / (1 + 1/2) - 2

Answer 4

sum([float(i) for i in input().split(', ')])

Assuming that the user enters a comma-separated (with a trailing space) list of numbers that can be parsed as valid floats.