python script for adding <BR> at the end of each newline

#!\bin\python
#copyright Usmar A Padow (amigojapan) 2015 usmpadow@gmail.com
#converts the newlines of a text file to line brakes in HTML
#usage text2html_newlines textfile.txt htmlfile.html
import sys
textfilename = sys.argv[1]
htmlfilename = sys.argv[2]
f = open(textfilename, 'r')
textfile = f.read()
html= textfile.replace('\n', '\n<BR>')
f = open(htmlfilename, 'w')
f.write(html)