python几个内置函数

1. filter

   故名思意，是过滤的意思

   >>> l
   [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
   >>> def f(x):
    if x%2 == 0:
     return True

   >>> f(4)
   True
   >>> filter(f,l)

   [0, 2, 4, 6, 8]

2. zip

>>> name=[‘xiaoming‘,‘xiaoli‘,‘xiaolan‘]
>>> age=[12,23,34]
>>> tel=[‘133‘,‘134‘,‘156‘]
>>> zip(name,age,tel)
[(‘xiaoming‘, 12, ‘133‘), (‘xiaoli‘, 23, ‘134‘), (‘xiaolan‘, 34, ‘156‘)]>>> test=[1,2]
>>> zip(name,age,tel,test)
[(‘xiaoming‘, 12, ‘133‘, 1), (‘xiaoli‘, 23, ‘134‘, 2)]

3.map

>>> map(None,name,age,tel)
[(‘xiaoming‘, 12, ‘133‘), (‘xiaoli‘, 23, ‘134‘), (‘xiaolan‘, 34, ‘156‘)]

>>> map(None,name,age,tel,test)
[(‘xiaoming‘, 12, ‘133‘, 1), (‘xiaoli‘, 23, ‘134‘, 2), (‘xiaolan‘, 34, ‘156‘, None)]
>>> a=[1,3,4]
>>> b=[5,6,7]
>>> def f(x,y):
 return x*y

>>> map(f,a,b)
[5, 18, 28]
>>> map(None,a,b)
[(1, 5), (3, 6), (4, 7)]
>>> map(f,a,b)
[5, 18, 28]

4.reduce

l=range(1,101)

>>> def f(x,y):
 return x+y

>>> reduce(f,l)
5050
>>> reduce(lambda x,y:x+y,l)
5050
>>>

通过实例可以看出这几个函数还是很有用处的。