第七天知识总结

文件操作：

# # 1.文件路径:分为绝对路径和相对路径
# # 2.编码方式：utf-8,jbk.....
# # 3.操作方式：只读，只写，追加，读写，写读

1.只读(r,rb)；加个b的意思是以bytes类型追加进去（在图片中用）

f = open('C:/Users/Administrator/Desktop/python例子.txt', mode='r', encoding='gbk')
content = f.read()
print(content)
f.close()
#
f = open('C:/Users/Administrator/Desktop/python例子.txt', mode='rb')
content = f.read()
print(content)
f.close()

2.只写(w,wb)，没有文件的话就创建，有就先将源文件内容删除再写

f = open('C:/Users/Administrator/Desktop/python例子.txt', mode='w',encoding='utf-8')
content = f.write('内容')
print(content)
f.close()
#
f = open('C:/Users/Administrator/Desktop/python例子.txt', mode='w',encoding='utf-8')
content = f.write('内容还有内容')
f.close()
#
f = open('C:/Users/Administrator/Desktop/python例子.txt', mode='wb')
content = f.write('内容sfs'.encode('utf-8'))
f.close()

3.追加（a）

f = open('C:/Users/Administrator/Desktop/python例子.txt', mode='a',encoding='utf-8')
content = f.write('，新的东西')
f.close()
#
f = open('C:/Users/Administrator/Desktop/python例子.txt', mode='ab',)
content = f.write('，好的天气'.encode('utf-8'))
f.close()

4.读写,只能先读再写，否则会出现占位;写读中,同理只能先写再读(w+;还有a+

f = open('C:/Users/Administrator/Desktop/python例子.txt', mode='r+',encoding='utf-8')
print(f.read())
print(f.write('，太阳'))
f.close()
#
f = open('C:/Users/Administrator/Desktop/python例子.txt', mode='r+b')
print(f.read())
print(f.write('，太阳1'.encode('utf-8')))
f.close()

5.查找时移动光标seek()

f = open('C:/Users/Administrator/Desktop/python例子.txt', mode='r+',encoding='gbk')
# content = f.read(2)     # 读出来的都是字符
f.seek(2)                 # 按照字节去定光标的位置
content = f.read()
print(content)
f.close()

6.告诉你光标的位置tell()

f = open('C:/Users/Administrator/Desktop/python例子.txt', mode='a+',encoding='gbk')
f.write('你好')
count = f.tell()
f.seek(count - 4)          # 只读最后两个
print(f.read())
f.close()

7.其他知识点

f = open('C:/Users/Administrator/Desktop/python例子.txt', mode='r+',encoding='gbk')
print(f.readable())               # 是否可读readable()，返回值时T或者F
print(f.readline())               # 一行一行的读
print(f.readlines())              # 每一行当成列表中的一个元素，添加到列表中
f.truncate()                        # 截取
f.close()

8.循环读取

f = open('C:/Users/Administrator/Desktop/python例子.txt', mode='r+',encoding='gbk')
for i in f:
    print(i.strip())          # strip去除换行
f.close()

9.with（打开时最后可以不用写close，同时还可以打开多个并进行多种操作，一般都是用的这种打开方式）

with open('C:/Users/Administrator/Desktop/python例子.txt', mode='r+',encoding='gbk') as f,\
    open('C:/Users/Administrator/Desktop/python例子.txt', mode='w+', encoding='gbk') as i:
with open('C:/Users/Administrator/Desktop/python例子.txt', mode='r+',encoding='gbk') as f:
    print(f.read())

10.课后作业:简单的实现用户注册登录

username_registered = input('请输入要注册的用户名')
password_registered = input('请输入要注册的密码')
with open('C:/Users/Administrator/Desktop/用户信息.txt', mode='w',encoding='utf-8') as f:
    f.write('{}\n{}'.format(username_registered,password_registered))
print('恭喜注册成功')
i = 0
lis = []
while i < 3:
    username = input('请输入用户名')
    password = input('请输入密码')
    with open('C:/Users/Administrator/Desktop/用户信息.txt', mode='r+',encoding='utf-8') as f1:
        for k in f1:
            lis.append(k)
    if username == lis[0].strip() and password == lis[1].strip():
        print('登录成功')
        break
    else:
        print('登录失败，请重新输入')
    i += 1