查看内置函数open详细说明
help(open)
dir(open)
函数实现
Open file and return a stream. Raise IOError upon failure.
open(file, mode='r', buffering=-1, encoding=None, errors=None, newline=None, closefd=True, opener=None)
Character Meaning
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'r' open for reading (default)
文件不存在，抛出异常
'w' open for writing, truncating the file first
文件不存在，创建文件；文件存在，打开并清空内容
'x' create a new file and open it for writing
文件不存在，创建文件；文件存在，报错
'a' open for writing, appending to the end of the file if it exists
追加模式：文件不存在则创建；存在则只追加内容
'b' binary mode 字节模式：读写都必须为字节
't' text mode (default)
'+' open a disk file for updating (reading and writing)
'U' universal newline mode (deprecated)
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The default mode is 'rt' (open for reading text). For binary random access, the mode 'w+b' opens and truncates the file to 0 bytes, while 'r+b' opens the file without truncation. The 'x' mode implies 'w' and raises an `FileExistsError` if the file already exists
读写模式区别：
r+ 读完文件后从头部覆盖写入
w+ 清空文件后写入
a+ 从尾部追加写入
x+ 新建文件后写入
查看文件详细说明
f = open('/xx/test.txt','r')
help(f)
dir(f)
文件常用方法