python学习-28 map函数

1.

num_1 = [10,2,3,4]

def map_test(array):
    ret = []
    for i in num_1:
        ret.append(i**2)     # 列表里每个元素都平方
    return ret
res = map_test(num_1)
print(res)

运行结果：

[100, 4, 9, 16]

Process finished with exit code 0

2.也可以用lambda

num_1 = [10,2,3,4]

def add_one(x):                       #  用匿名函数就不用定义这里
    return x+1
def reduce_one(x):                    #  用匿名函数就不用定义这里
    return x-1

def map_test(func,array):
    ret = []
    for i in array:
       res= func(i)
       ret.append(res)
    return ret

print(map_test(add_one,num_1))
print(map_test(lambda x:x+1,num_1))          # 也可以用 直接用匿名函数，就不用定义前面那些函数了

print(map_test(reduce_one,num_1))
print(map_test(lambda x:x-1,num_1))           # 匿名函数

print(map_test(lambda x:x**2,num_1))          # 匿名函数

运行结果：

[11, 3, 4, 5]
[11, 3, 4, 5]
[9, 1, 2, 3]
[9, 1, 2, 3]
[100, 4, 9, 16]

Process finished with exit code 0

3. map函数 将字符串改成大写

msg = 'abc'
res = list(map(lambda  x:x.upper(),msg))
print(res)

运行结果:

['A', 'B', 'C']

Process finished with exit code 0