更改列表中的类型

定量数据通常作为字符串读入，在处理之前必须将其转换为数字类型。可以使用 List Comprehension 或 map() 函数转换所有列表项的类型。

# Convert a list of strings to integers.
items = ["1","2","3","4"]
[int(item) for item in items]
# Out: [1, 2, 3, 4]

# Convert a list of strings to float.
items = ["1","2","3","4"]
map(float, items)
# Out:[1.0, 2.0, 3.0, 4.0]