How to use python remove the '^M' when copy words from Windows to Linux

今天帮同事用Python写了一个小工具，实现了在linux下批量文件名和去掉windows 文件到linux过程中产生^M的脚本，代码如下：

 !/opt/exptools/bin/python
 import os,os.path,sys
 import shutil,string
 dir ='/home/alzhong/tools/zch/filedir'

 for i in os.listdir(dir):

     newfile = i.replace('.s.txt','.s')

     oldfullfile = dir+"/"+i
     newfullfile = dir+'/'+newfile
         #corrform_cmd="winrar a '%s' %s" % (target, source)
     try:
         corrform_cmd="cat %s | tr -d \"\r\" > %s"%(oldfullfile, newfullfile)
         os.system(corrform_cmd)
         print "%s transform to %s successfully!"%(i, newfile)
     except:
         print "%s transform to %s failed!"%(i, newfile)
     try:
         rm_cmd="rm -rf %s"%(oldfullfile)
         os.system(rm_cmd)
         print "%s removed successfully!"%(i)
     except:
         print "%s removed failed!"%(i)
     #shutil.move(oldfullfile,newfullfile)