用法1：如函数 f(x) = x * x，用python实现如下

>>> def f(x):

...     return x * x

>>> r = map(f, [1, 2, 3, 4, 5, 6, 7, 8, 9])

>>> list(r)

[1, 4, 9, 16, 25, 36, 49, 64, 81]

结果：数组个数不变

用法2：

把这个list所有数字转为字符串

>>> list(map(str, [1, 2, 3, 4, 5, 6, 7, 8, 9]))

['1', '2', '3', '4', '5', '6', '7', '8', '9']


用法3

dict_a = [{'name': 'python', 'points': 10}, {'name': 'java', 'points': 8}]

map(lambda x : x['name'], dict_a)

输出  ['python', 'java']

用法4

list_a = [1, 2, 3]

list_b = [10, 20, 30]

map(lambda x, y: x + y, list_a, list_b)

输出 [11, 22, 33]