map()reduce()filter()总结

Posted 2020-11-10 gl-gl

map()函数：处理序列中的每一个元素，得到的结果是一个迭代器形式，该迭代器的位置以及元素个数与原来一样。可以处理任何可迭代序列

filter()函数：遍历序列中的每一个元素，判断每个元素得到的布尔值，如果是True则留下来

1 people=[{‘name‘:‘alex‘,‘age‘:1000,
2          ‘name‘:‘alex2‘,‘age‘: 10000,
3          ‘name‘:‘alex3‘,‘age‘: 9000,
4          ‘name‘:‘alex4‘,‘age‘: 35,
5          ‘name‘:‘alex5‘,‘age‘: 18,}]
6 res=(list(filter(lambda x:x[‘age‘]<=100,people)))
7 print(res)

[{‘name‘: ‘alex5‘, ‘age‘: 18}]

Process finished with exit code 0

　

 1 movie_perple = [‘chenchensb_‘,‘linlin‘,‘guoguo0‘,‘wowowsb_‘,‘dascsasb_‘]
 2 # lambda x:x.endswith(‘sb_‘)
 3 def filte(func,x):
 4     array=[]
 5     for i in x:
 6         if not func(i):
 7             array.append(i)
 8     return array
 9 # res1=filter_test(lambda x:x.endswith(‘sb_‘),movie_perple)
10 # res2=filter_test(lambda x:x.startswith(‘c‘),movie_perple)
11 print(filter(lambda x:x.endswith(‘sb_‘),movie_perple))
12 print(list(filter(lambda x:x.endswith(‘sb_‘),movie_perple)))
13 print(list(filter(lambda x:not x.endswith(‘sb_‘),movie_perple)))
14 # print(res1)
15 # print(res2)

运行结果：

1 <filter object at 0x02D8FCD0>
2 [‘chenchensb_‘, ‘wowowsb_‘, ‘dascsasb_‘]
3 [‘linlin‘, ‘guoguo0‘]
4 
5 Process finished with exit code 0

 

reduce()函数：处理一个序列，然后把序列进行合并

1 from functools import reduce
2 num_l=[1,2,3,4,5]
3 # reduce(函数,可迭代对象，初始值)
4 print(reduce(lambda x,y:x+y,num_l,100))

 

 1 list=[1,2,3,5,6]
 2 def reduce_num(func,array,init=None):
 3     if init is None:
 4         res=list.pop(0)
 5     else:
 6         res=init
 7     for num in array:
 8         res=func(res,num)
 9     return res
10 result=reduce_num(lambda x,y:x*y,list,100)
11 print(result)

运行结果：

18000

Process finished with exit code 0