python3 内置函数 filter()

filter(function or None, iterable) --> filter object

Return an iterator yielding those items of iterable for which function(item)
is true. If function is None, return the items that are true.

函数有两个参数，第一个可以为一个函数，或者None,第二个参数为一个可迭代对象

保返回真值(非零，非空)返回值为一个filter object

1 ls = [1, 0 -1, 3]
2 
3 l =(filter(None,ls))
4 print(l)
5 
6 <filter object at 0x0000023036E7A390>

filter1

这个filter　object 是个可迭代对象

 1 ls = [1, 0 -1, 3]
 2 
 3 def t(x ):
 4     if x > 0:
 5         return True
 6     else:
 7         return False
 8     
 9 l =(filter(t,ls))
10 for i in l:
11     print(i)
12 
13 1
14 3

filter2

python3 内置函数 filter()

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