python基础计算！

计算 s=1−1/2+1/3−1/4+…+1/99−1/100
用for循环

result = 0
for i in range(1,101):
    if i%2==0:
        result  = result - 1/i
    else:
        result  = result + 1/i
print(result)

nsum = 0
a = 1
for i in range(1, 101):
    nsum += (a / i)
    a = -a

print(nsum)

s=0
for i in range(1,101):
    s+=(-1)**(i-1)*(1/i)
print(s)