如何在列表、字典、集合中根据条件筛选数据
问题举例：
过滤列表[1, 2, 5, -1, 9, 10]中的负数
筛选字典{“zhangsan”:97, "lisi":80, "wangwu":60, "liqiang":91}中的值高于90的键值对
筛选集合{89, 70, 60, 80, 90}中能被3整除的元素
列表
一般遇到这种问题，我们首先会想到用for循环的方式去解决
（1）for循环
from random import randint nums = [randint(-10, 10) for _ in range(20)] #生成一个列表 res_list = [] for ele in nums: if ele > 0: res_list.append(ele)
但是这种方式并不pythonic
（2）列表解析
from random import randint nums = [randint(-10, 10) for _ in range(20)] res_list = [ele for ele in nums if ele > 0] #list comprehension
（3）filter函数
from random import randint nums = [randint(-10, 10) for _ in range(20)] res_filter = filter(lambda x: x > 0, nums) #filter res_list = list(res_filter)
字典
（1）字典解析
from random import randint grade_info = {"stu%d" % i: randint(50, 100) for i in range(10)} res_dict = {k: v for k, v in grade_info.items() if v > 70}
（2）filter函数
from random import randint grade_info = {"stu%d" % i: randint(50, 100) for i in range(10)} res_filter = filter(lambda item: item[1] > 70, grade_info.items()) res_dict = dict(res_filter)
集合
集合解析
from random import randint nums_set = {randint(10, 20) for _ in range(20)} nums_res = {ele for ele in nums_set if ele % 3 == 0}
filter函数
from random import randint nums_set = {randint(10, 20) for _ in range(10)} nums_filter = filter(lambda x: x % 3 == 0, nums_set) nums_res = set(nums_filter)
参考资料：python3实用编程技巧进阶