python写一段脚本代码自动完成输入（目录下的所有）文件的数据替换（修改数据和替换数据都是输入的）

import sys,os,os.path
def file_replace():
	path = sys.argv[1]
	old_data = sys.argv[2]
	new_data = sys.argv[3]
	if not os.path.exists(path):
		print 'file of dir does not exists!\n'
		return
	elif os.path.isdir(path):	
		for root,dirs,files in os.walk(path):
			for fn in files:
				filepath = os.path.join(root,fn)
				f = open(filepath,'r+')
				line = f.readlines()
				f.seek(0)
				for s in line:
					f.write(s.replace(old_data,new_data))
				f.close()
	elif os.path.isfile(path):
		f = open(path,'r+')
		line = f.readlines()
		f.seek(0)
		for s in line:
			f.write(s.replace(old_data,new_data))
		f.close()
	else:
		print 'argv[1] illegal,not a file or dir\n'
		return
if __name__=='__main__':
	file_replace()