Python 中filter函數用法

filter()和map一樣，接收一個函數和一個序列。和map不同的是，filter()把傳入的函數依次作用於每個元素，然后根據返回值是True還是False決定保留還是丟棄該元素

過濾出奇數：

def   is_odd(n):
    return n%2==1

print  filter(is_odd,[1,2,3,4,5])    # ==>[1, 3, 5]

 過濾掉空字符串：

def   not_empty(s):
    return  s  and  s.strip()     

print  filter(not_empty,['A','','B',None,'C','  '])   # ==>['A', 'B', 'C']
 

 

L=range(1,101)
def  iseven(x):
    return  x%2==0

print filter(iseven,L)
#[2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92, 94, 96, 98, 100]