22.Python：文件操作模式详解

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# 以t模式为基准操作

# 1.r:只读模式:文件不存在时报错，文件存在时指针跳到开始位置

# input_username = input("username:")
# input_password = input("password:")
#
# with open('a.txt', mode='rt', encoding='utf-8') as f:
#     for line in f:      # 读取f的每一行
#         username, password = line.strip().split(':')
#
#         if input_username == username and input_password == password:
#             print('login successful')
#             break
#     else:
#         print('wrong username or password')

# 2.w:只写模式:文件不存在时会创建空文件，文件存在时会清空文件，指针跳到开始位置
# with open('c.txt', mode='wt', encoding='utf-8') as f:
#     f.write('哈哈哈\n')

# 强调1：在以w模式打开文件没有关闭的情况下，连续写入，新内容总是跟在旧内容之后
# with open('c.txt', mode='wt', encoding='utf-8') as f:
#     f.write('哈哈哈1')
#     f.write('哈哈哈2\n')
#     f.write('哈哈哈3\n')

# 3.a:只追加写模式:文件不存在时创建空文档，文件存在时，指针会直接跳到文件末尾
# with open('c.txt', mode='at', encoding='utf-8') as f:
#     f.write('哈哈哈4\n')

# 注册功能
# name = input("user name:")
# password = input("password:")
#
# with open("info.txt", mode="at", encoding="utf-8") as f:
#     f.write('{}:{}\n'.format(name, password))

# 文件copy工具
# src_file = input("path1:").strip()
# dst_file = input("path2:").strip()
# with open(r'{}'.format(src_file), mode='rt', encoding='utf-8') as f1, \
#      open(r'{}'.format(dst_file), mode='wt', encoding='utf-8') as f2:
#     res = f1.read()
#     f2.write(res)

# 4.+:不能单独使用，必须配合r,w,a      # 了解
with open('a.txt', mode='rt+', encoding='utf-8') as f:
    f.write('aaa')      # 覆盖原来内容

with open('a.txt', mode='wt+', encoding='utf-8') as f:
    f.write('aaa')

with open('a.txt', mode='at+', encoding='utf-8') as f:
    f.write('aaa')

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