python 遍历列表，替换元素

Question

names=['xiaoming','fangfang','lili']
如何遍历names列表，输出每个元素的索引和元素。当索引为偶数时，把对应的元素改为－1。

Answer 1

```python

names = ['xiaoming', 'fangfang', 'lili']
for index, name in enumerate(names):
    if index % 2 == 0:
        names[index] = -1
print(index, name)
print(names)  # 输出 [-1, 'fangfang', -1]

```