python 3文件內容替換

在原有的文件上，修改替換，並放到新的文件裏

old = open('day','r')
new = open('new_day','w')
old_replace = input('please replace content:')
new_replace = input('please new replace content:')

for i in old:
    if old_replace in i:
        i = i.replace(old_replace,new_replace)
    new.write(i)

old.close()
new.close()