第五章文件处理

1. CopyTool练习

'''
练习，利用b模式，编写一个cp工具，要求如下：

　　1. 既可以拷贝文本又可以拷贝视频，图片等文件

　　2. 用户一旦参数错误，打印命令的正确使用方法，如usage: cp source_file target_file

　　提示：可以用import sys，然后用sys.argv获取脚本后面跟的参数
'''

import sys
if len(sys.argv) != 3:
    print('usage: cp source_file target_file')
    sys.exit()

source_file, target_file=sys.argv[1],sys.argv[2]
with open(source_file, 'rb') as read_f,open(target_file, 'wb') as write_f:
    for line in read_f:
        write_f.write(line)

print(type(sys.argv[1]))

# with open("source.jpeg",'rb') as read_f,open("target.png",'wb') as write_f:
#     for line in read_f:
#         write_f.write(line)

2. 光标移动练习

"""
练习：基于seek实现动态监测文件中是否有新内容的添加
"""


import time
with open('a.txt', 'rb') as f:
    f.seek(0, 2)
    while True:
        line = f.readline()
        if line:
            print(line.decode('utf-8'))
            print(f.tell())
        else:
            time.sleep(2)
            print(f.tell())

3. 文件更改练习

"""
1. 文件a.txt内容：每一行内容分别为商品名字，价钱，个数，求出本次购物花费的总钱数
apple 10 3
tesla 100000 1
mac 3000 2
lenovo 30000 3
chicken 10 3

2. 修改文件内容，把文件中的mac都替换成linux
"""

import os
with open("a.txt", "r") as read_f:
    read_f = read_f.read()
    items = read_f.replace("\n", " ")
    item_lst = items.split()
    s = 0
    for i in range(1, len(item_lst) + 1, 3):
        amount = int(item_lst[i]) * int(item_lst[i+1])
        s += amount
    print("本次购物总金额为：", s)

with open('a.txt') as read_f,open('.a.txt.swap','w') as write_f:
    for line in read_f:
        line=line.replace('mac','linux')
        write_f.write(line)

os.remove('a.txt')
os.rename('.a.txt.swap','a.txt')