Day3-Modify file

# open w, 会覆盖文件，一般修改文件，我们会新建一个加判断修改写入新文件。不在旧文件上操作。
f=open("yesterday",'r',encoding="utf-8")
f_new = open("yesterday.bak",'w',encoding="utf-8")
for line in f:
    if "first" in line:
        line = line.replace("first","new")
    f_new.write(line)
f.close()
f_new.close()
#----------------------------参数化-------------
import sys
f=open("yesterday",'r',encoding="utf-8")
f_new = open("yesterday.bak",'w',encoding="utf-8")
find_str = sys.argv[1]
replace_str = sys.argv[2]
for line in f:
    if find_str in line:
        line = line.replace(find_str,replace_str)
    f_new.write(line)
f.close()
f_new.close()