Python如何从关联列表中删除符合指定条件的对应元素

现有两个一一对应的平行关联列表：

• Names：存储人员姓名
• Fees：存储同索引位置人员的缴费状态，"y"代表已缴费，"n"代表未缴费
  需求为移除所有未缴费人员对应的姓名、缴费状态条目。原有实现代码运行时会触发索引越界，且删除结果不符合预期，原代码如下：

Names = ["a","b","c","d","e","f"]
Fees = ["n","y","y","y","n","y"]

print("Names:",Names)
print("Fees paid:",Fees)

for i in range (0,len(Fees)):
    if Fees[i] == "n":
        del(Names[i])
        del(Fees[i])

print("Names:",Names)
print("Fees paid:",Fees)

原代码的核心问题是正向遍历列表的同时动态删除列表元素：

1. range(0,len(Fees))在循环启动时就会按照初始列表长度生成固定的索引序列，删除元素后列表实际长度变短，遍历到后面就会出现索引超出当前列表长度的越界错误。
2. 删除某索引位置的元素后，该位置后面的所有元素都会向前移位，下一轮循环遍历下一个索引时，会直接跳过原本移位到当前索引位置的元素，导致漏判。

方案1：倒序遍历删除 #

从列表末尾往头部方向遍历，此时删除元素只会影响已经遍历过的后部索引，不会干扰还未遍历的前部元素位置，不会出现漏判和越界：

Names = ["a","b","c","d","e","f"]
Fees = ["n","y","y","y","n","y"]

print("Names:",Names)
print("Fees paid:",Fees)

# 从最后一个索引倒序遍历到索引0
for i in range(len(Fees)-1, -1, -1):
    if Fees[i] == "n":
        del Names[i]
        del Fees[i]

print("Names:",Names)
print("Fees paid:",Fees)

运行输出：

Names: ['a', 'b', 'c', 'd', 'e', 'f']
Fees paid: ['n', 'y', 'y', 'y', 'n', 'y']
Names: ['b', 'c', 'd', 'f']
Fees paid: ['y', 'y', 'y', 'y']

方案2：列表推导式过滤（推荐写法） #

Python中更推荐不直接修改原列表，而是通过配对过滤生成新列表，逻辑更清晰，完全避免遍历修改原列表的坑：

Names = ["a","b","c","d","e","f"]
Fees = ["n","y","y","y","n","y"]

print("Names:",Names)
print("Fees paid:",Fees)

# 打包同索引的姓名和缴费状态，过滤出已缴费的配对
paid_records = [item for item in zip(Names, Fees) if item[1] == "y"]
# 拆分回两个列表
Names, Fees = list(zip(*paid_records))

print("Names:",Names)
print("Fees paid:",Fees)

运行结果和方案1完全一致。

内容的提问来源于stack exchange，提问作者Mr mac