python笔记（四）

例一：

def f(x,y):
    return x*y
print f(2,3)

g=lambda x,y:x*y
print g(1,2)

例二：def f(n):
    if n>0:
        n*f(n-1)
print f(5)

结果：TypeError: unsupported operand type(s) for *: 'int' and 'NoneType'

l=range(1,6)

def f(x,y):
    return x*y

print reduce(f,l)

引入函数：reduce

 

改进版：print reduce(lambdax,y:x*y,l)

Switch语句：

from __future__ import division#模块产生小数点

def jia(x,y):
    return x+y
def jian(x,y):
    return x-y
def cheng(x,y):
    return x*y
def chu(x,y):
    return x/y

operator ={'+':jia,'-':jian,'*':cheng,'/':chu}
def f(x,o,y):
    print operator.get(o)(x,y)
f(3,'+',2)

 

内置函数：len()长度：

print divmod(5,2)

结果：（2,1）

print isinstance(l,list)#判断类型

print cmp('hello','h')#判断字符串是否相等

print tuple(l)#类型的转化

字符串处理函数：

例一：s='hello world'
print s
print str.capitalize(s)#首字母大写
print s.replace("hello",'good')#代替函数
ss='123123123'
print ss.replace('1','x',2)
ip='192.168.123.52'
print ip.split('.',2)#切割函数

结果：hello world

Hello world

good world

x23x23123

['192', '168', '123.52']

序列处理函数：

例二：

a=[1,3,5]
b=[2,4,6]
def mf(x,y):
    return x*y
print map(None,a,b)
print map(mf,a,b)

结果：[(1, 2), (3, 4), (5, 6)]

      [2, 12, 30]

例三：print zip(name,age,tel)
print map(None,name,age,tel)

结果：[('milo', 20, '133'), ('zou', 30, '123'), ('tom', 40, '456')]

[('milo', 20, '133'), ('zou', 30, '123'), ('tom', 40, '456')]

例四：l=range(1,101)
def rf(x,y):
    return x+y
print reduce(rf,l)

结果：5050

例五：

print filter(lambdax:x%2==0,l)

取出偶数