写一个脚本，允许用户按以下方式执行时，可以对指定文件内容进行全局替换

# 练习1：写一个脚本，允许用户按以下方式执行时，可以对指定文件内容进行全局替换
# python pyScript.py oldStr newStr fileName

import os
import sys

oldStr = sys.argv[1]
newStr = sys.argv[2]
fileName = sys.argv[3]

# print(oldStr)
# print(newStr)
# print(fileName)


newFileName = '%s.new'%fileName

f = open(fileName,"r")
fNew = open(newFileName,"w")

# print(f.readlines())

for line in f:
    # print(line)
    if oldStr in line:
        line = line.replace(oldStr,newStr)
    fNew.write(line)

f.close()
fNew.close()
os.replace(newFileName,fileName)