python小函数

python小函数

# coding:gbk

import  os,sys,time

def  get_ext(fileName):
    pos  =  fileName.rfind( " . " )
     if  pos  !=- 1 :
         return  fileName[pos:].lower()
     else :
         return  None

def  str2int(v):
     try :v  =  int(v)
     except :v  =  0
     return  v

def  mod(x,y):
     return  float(x) / y

def  printf(format, * args):
    sys.stdout.write(format % args)

def  sprintf(format, * args):
     return  format % args

def  exit_delay(num):
    secnod  =  num
    text  =  r " after (%02d) secnod exit. "
    length  =  len(text) - 2
    back  =   ""
     for  i  in  range(length):
        back  =  back  +   " \b "
     while  (secnod):
        sys.stdout.write(text % secnod)
        sys.stdout.flush()
        time.sleep( 1 )
        sys.stdout.write(back)
        secnod  =  secnod  - 1 ;
    sys.stdout.write(text % secnod)
    sys.stdout.write( " \r\n " )
    
def  unlink(filename):
     try :
        os.remove(filename)
        printf( " 删除文件(%s)成功 \r\n " ,filename)
     except  WindowsError,e:
         if  e.errno == 2 :
            printf( " 文件(%s)不存在 \r\n " ,filename)
            
def  A(n):
    c  =   1
     for  i  in  range(n):
        c  *=  i + 1
     return  c

def  C(n,m):
     return  A(n) / A(n - m) / A(m)