函数式编程

这里主要介绍map,reduce,sorted,filter的使用

1.map:是一种映射，不改表原来的列表，而是返回一个新的列表

格式:map(函数，可迭代对象)

eg:

def get_sum(n):
    '''
    定义一个列表求和
    '''
    ret=0
    for i in n:
        ret +=i
    return ret
nums = [
    [1,3,4],
    [2,4,5],
    [2,4,8]
 ]
print(list(map(get_sum,nums)))
结果为:[8, 11, 14]

2.reduce,合并,在python3中，需要导入from functools import reduce

格式reduce(函数，可迭代对象)

eg:

def get_sum(x,y):
    '''
    定义一个reduce求和
    '''
    return x+y
from functools import reduce
nums =[1,2,3,4,5,6,7]
print(reduce(get_sum,nums))
#结果为:28

3.sorted 排序

格式sorted(可迭代对象，key=自定义函数)

students = [
    {"name":'eric',"score":[70,50,40]},
    {"name":'ben',"score":[70,90,40]},
    {"name":'gavin',"score":[70,100,189]}
]

def get_score_sum(a,b):
    return sum(a['score']) - sum(b['score'])
from functools import cmp_to_key
print(sorted(students,key=cmp_to_key(get_score_sum),reverse=True)) #倒序

4.filter,过滤信息

格式filter(函数，可迭代对象)

a =  ['sb','***','flg','xxx','+1秒']
b = [ 'sb','***','flg','hello','python', 'xxx','+1秒']
print(list(filter(lambda x:x not in a,b)))
#结果为:['hello', 'python']