如果列表的第n个元素通过条件，如何选择另一个列表的第n个元素？

Question

如果pair_length的第n个元素通过条件，那么我想将x_cords，y_cords和pair_num的第n个元素写入输出文件。例如，如果pair_length列表的第3个元素通过条件length <= average_pair_length():，那么我想选择x_cords，y_cords和pair_num列表的第3个元素，以便可以将它们写入输出文件。我尝试使用filter（）函数，但没有返回我想要的。这是我的代码：

pair_length = []
pair_nums = []
x_cords = []
y_cords = []
for line in islice(data, 1, None):
    fields = line.split("   ")
    pair_num = float(fields[0])
    pair_nums.append(pair_num)
    x_cord = float(fields[1])
    x_cords.append(x_cord)
    y_cord = float(fields[2])
    y_cords.append(y_cord)
    vector_length = sqrt(x_cord**2 + y_cord**2)
    pair_length.append(vector_length)

def average_pair_length():
    average = mean(pair_length)
    return average

index = 0
for index, length in enumerate(pair_length):
    if length <= average_pair_length():
    #this is where I want to find the nth element of pair_length so I can find the nth elements in the other lists

Answer 1

使用index确定它在数组中是哪个元素

for index, length in enumerate(pair_length): # index tells you which element it is
    if length <= average_pair_length():
        pair_nums[index] = new_pair_num # assign the new value here
        x_cords[index] = new_x_cord # assign the new value here
        y_cords[index] = new_y_cord # assign the value here