python-文件操作

# open() 方法的介绍
open(...)
    open(name[, mode[, buffering]]) -> file object
    
    Open a file using the file() type, returns a file object.  This is the
preferred way to open a file.  See file.__doc__ for further information.
# 查看file.__doc__
>>> print(file.__doc__)
file(name[, mode[, buffering]]) -> file object

Open a file.  The mode can be 'r', 'w' or 'a' for reading (default),
writing or appending.  The file will be created if it doesn't exist
when opened for writing or appending; it will be truncated when
opened for writing.  Add a 'b' to the mode for binary files.
Add a '+' to the mode to allow simultaneous reading and writing.
If the buffering argument is given, 0 means unbuffered, 1 means line
buffered, and larger numbers specify the buffer size.  The preferred way
to open a file is with the builtin open() function.
Add a 'U' to mode to open the file for input with universal newline
support.  Any line ending in the input file will be seen as a '\n'
in Python.  Also, a file so opened gains the attribute 'newlines';
the value for this attribute is one of None (no newline read yet),
'\r', '\n', '\r\n' or a tuple containing all the newline types seen.

'U' cannot be combined with 'w' or '+' mode.
# 文件打开模式对比关系

    r ，只读模式【默认】
    w，只写模式【不可读；不存在则创建；存在则清空内容；】
    x， 只写模式【不可读；不存在则创建，存在则报错】
a， 追加模式【可读；   不存在则创建；存在则只追加内容；】
# 字节的方式打开
1.    只读 rb
2.    只写 wb
3.    追加 ab
# 测试用例
#!/usr/bin/env python
# -*- coding:utf-8 -*- 

if __name__ == '__main__':
    'functions is test open '
    file1 = open('first.py','r+',encoding='utf-8')
    print("打印该文件内容")
    print(file1.read())
    file1.write("This is a test open file function")
    print(file1.read())
    file1.close()
    if file1.closed :
        print("这个文件已经关闭。")
    else:
        file1.close()
# 在Python 3.X 版本以上，open 方法
open(file, mode='r', buffering=-1, encoding=None, errors=None, newline=None, closefd=True, opener=None)
Open file and return a stream.
 
如果是以字节的形式访问
#!/usr/bin/env python
# -*- coding:utf-8 -*- 

if __name__ == '__main__':
    'functions is test open '
    file1 = open("two.py","wb")
    file1.write(bytes("BONC，让数据改变工作和生活",encoding="gbk"))
    file1.close()
    file2 = open("two.py",'r')
    print(file2.read())
file2.close()

## 普通模式打开，Python 内部提供机制将 二进制代码转换为 字符字符串
# 计算机的存储单元是 0 1 
# 文件指针 file.seek, file.tell
# 读文件可以在指针位置读写，写文件一般是在末尾追加，指针移动到末尾。
# w+ 先清空，在写的之后，就可以读了。
# mode a （追加）打开文件的时候已经将文件指针移动到文件尾部。