python 判断文件是否存在以及

def test1():    #判断文件夹是否存在：    if os.path.exists(r'D:\PythonFiles\CINS\traindata\2016103000.news_zhengwen'):        print 'true'    else:        print 'false'#test1()#整数转换字符串def test2():    sum = 1223    str='%d' % sum    print sum , type(sum)    print str , type(str)#test2()#判断地址链接def test3():    s=r'D:\PythonFiles\CINS\traindata\2017021300.news_zhengwen'    print s    sum =0    intConvertStr='%d' % sum    str = intConvertStr + '.news_zhengwen'    strbase =r'D:\PythonFiles\CINS\traindata\\'+str    print strbasetest3()