文件处理：
文件的打开模式b模式
#1、与t模式类似不能单独使用因为单独的r、w、a是mode默认为字符串‘t’，所以必须是rb，wb，ab
#2、b模式下读写都是以bytes单位的
#3、b模式下一定不能指定encoding参数
#rb模式：只读二进制模式
# with open('xxx.jpg',mode='rb',) as f:
# data=f.read()
# print(data,)
# print(type(data))
# with open('db.txt',mode='rb',) as f:
# data=f.read() #
# print(data.decode('utf-8')) #bytes-----unicode
# print(type(data))
#wb模式：只写二进制模式
# with open('b.txt',mode='wb') as f:
# msg='你好啊，xxx'
# f.write(msg.encode('gbk'))
# with open('b.txt',mode='wb') as f:
# msg='你好啊，xxx'
# f.write(msg.encode('utf-8'))
# with open('xxx.txt',mode='rb') as f:
# data=f.read()
# # print(type(data))
# print(data.decode('utf-8'))
# with open('x.jpg',mode='rb') as f:
# data=f.read()
# print(type(data))
# print(data.decode('utf-8'))
#ab模式：二进制追加模式
# with open('x.txt',mode='ab') as f:
# f.write('你好'.encode('utf-8'))
# with open('xxx.jpg','rb') as f:
# for line in f:
# print(line)
#可读可写：r+t
# with open('x.txt','r+t',encoding='utf-8') as f:
# # print(f.readable())
# # print(f.writable())
# print(f.readline())
# f.write('\nxxxxxxxxxxxxxx\n')
#w+t：可写可读
#a+t：追加可写可读
#偏移光标：
# with open('user.txt','r+',encoding='utf-8') as f:
# f.seek(6) #偏移量的单位是字节
# # print(f.tell())
# print(f.read())
# with open('user.txt','r+',encoding='utf-8') as f:
# f.seek(6) #偏移量的单位是字节
# # print(f.tell())
# f.write('[稻衍田鸡]')
#1、先把文件内容全部读入内存
#2、然后在内存中完成修改
#3、再把修改后的结果覆盖写入原文件
#缺点：会在文件内容过大的情况下，占用过多的内存
# with open('user.txt',mode='r',encoding='utf-8') as f:
# data=f.read()
# data=data.replace('稻衍田鸡','刘锦[比egon还帅的男人]')
#
# with open('user.txt',mode='w',encoding='utf-8') as f:
# f.write(data)
#修改文件方式二：
#1、以读的方式打开原文件，以写的方式打开一个新文件
# import os
#
# with open('user.txt',mode='rt',encoding='utf-8') as read_f,\
# open('user.txt.swap',mode='wt',encoding='utf-8') as write_f:
#
# for line in read_f:
# if '成群' in line:
# line=line.replace('成群','锦[比egon还帅的男人]')
#
# write_f.write(line)
os.remove('user.txt')
os.rename('user.txt.swap','user.txt')
