python例子

例一：for循环

for i in range(1,100):
        if i==23:
            print "great,%s you got your lucky number:" %(i)
            break
        else:
            print 'the number is :',i

运行：windows下切换到目录下 Python xunhuan.py

linux 下 cd到目录下 Python xunhuan.py

例二：阶乘的例子

n=int(input('Enter an integer >=0:'))
fact=1
for i in range(2,n+1):
    fact=fact*i;
print(str(n)+'factorial is'+str(fact))

例三：while循环

total=0
s=raw_input('Enter a number(or done):')
while s !='done':
    num=int(s)
    total=total+num
    s=raw_input('Enter a number(or done):')
print('The sum is '+str(total))

例四：九九乘法表

for i in range(1,10):
    for j in range(1,i+1):
        print j, 'x', i, '=', j*i, '	',
    print '
'
print 'done'

例五、函数定义

import math
def move(x,y,step,angle=0):
    nx=x+step*math.cos(angle)
    ny=y+step*math.sin(angle)
    return nx,ny
x, y = move(100, 100, 60, math.pi / 6)
print x,y

例六、可变参数函数

import math
def calc(*numbers):
    sum = 0
    for n in numbers:
        sum = sum + n * n
    return sum
y=calc(1, 2,3,4)
print y

例七：递归函数

def fact(n):
    if n==1:
        return 1
    return n*fact(n-1)
    
y=fact(5)
print y

例八：尾递归的递归函数

只返回函数本身

def fact(n):
    return fact_iter(1, 1, n)

def fact_iter(product, count, max):
    if count > max:
        return product
    return fact_iter(product * count, count + 1, max)
    
y=fact(5)
print y

例九：高阶函数

def add(x, y, f):
    return f(x) + f(y)
print add(-5, 6, abs)

把函数作为参数传入，这样的函数称为高阶函数，函数式编程就是指这种高度抽象的编程范式。

例十：字典

color={'red':1,'blue':2,'gree':3}
print color['gree']
color['gree']=0
print color

例十一：一个ping程序

import subprocess

cmd="cmd.exe"
begin=50
end=54
while begin<end:

    p=subprocess.Popen(cmd,shell=True,stdout=subprocess.PIPE,
                   stdin=subprocess.PIPE,
                   stderr=subprocess.PIPE)
    p.stdin.write("ping 10.10.0."+str(begin)+"
")

    p.stdin.close()
    p.wait()
    begin=begin+1

    print "execution result: %s"%p.stdout.read()

例十二：os模块

#!/usr/bin/env python
# -*- coding:gbk -*-
import os  
for fileName in os.listdir ( 'd:\' ):                
    print fileName

例十三：创建目录

#!/usr/bin/env python
# -*- coding:gbk -*-
#Python对文件系统的操作是通过os模块实现
import os  
for fileName in os.listdir ( 'd:\' ):                
    print fileName
print "**************"
os.mkdir("d:\dgx")
for fileName in os.listdir ( 'd:\' ):                
    print fileName

例十四：写入读取的内容到文件

#!/usr/bin/env python
import os
ls=os.linesep
while True:
    fname = raw_input('Enter file name: ')
    if os.path.exists(fname):
        print "Error:%s already exists " 
    else:
        break
all = []

print "
Enter lines('.'by itself to quit)"

while True:
    entry=raw_input('>')
    if entry =='.':
        break
    else:
        all.append(entry)

fobj=open(fname,'w')
fobj.write('
'.join(all))
fobj.close()
print 'Done'

例十五：读取文件内容

#!/usr/bin/env python

fname=raw_input('Enter filename:')


try:
    fobj=open(fname,'r')
except IOError,e:
    print "*******file open error:",e
else:
    for eachLine in fobj:
        print eachLine,
    fobj.close()

例十六：第一个main

#-*-coding:utf-8-*-
import sys
def Main():  
    sys.stdout.write("开始程序
")
    str1='i am "python"
'
    str2="i am 'python'
"
    str3="""
            i'm "python",
            <a href="http://www.sina.com.cn"></a>
            """
    print str1,str2,str3
if  __name__ == '__main__':
    Main()

例十七：函数的默认参数与返回值

#-*-coding:utf-8-*-
import sys
def arithmetic(x=1,y=1,operator="+"):
    result={
        "+":x+y,
        "-":x-y,
        "*":x*y,
        "/":x/y         
    }
    return result.get(operator)
if __name__=="__main__":
    print arithmetic(1, 2)
    print arithmetic(1, 2, "/")