刚刚学完文件操作，现学现卖，这就整理起来咯。文件的操作，归根结底就只有两种：打开文件、操作文件
一、打开文件：文件句柄 = open('文件路径', '模式')
python中打开文件有两种方式，即：open(...) 和 file(...)，本质上前者在内部会调用后者来进行文件操作，在这里我们推荐使用open，解释
二、操作文件
操作文件包括了文件的读、写和关闭，首先来谈谈打开方式：当我们执行 文件句柄 = open('文件路径', '模式') 操作的时候，要传递给open方法一个表示模式的参数：
打开文件的模式有：
- r，只读模式（默认）。
- w，只写模式。【不可读；不存在则创建；存在则删除内容；】
- a，追加模式。【可读； 不存在则创建；存在则只追加内容；】
"+" 表示可以同时读写某个文件
- r+，可读写文件。【可读；可写；可追加】
- w+，先写再读。【这个方法打开文件会清空原本文件中的所有内容，将新的内容写进去，之后也可读取已经写入的内容】
- a+，同a
"U"表示在读取时，可以将 \r \n \r\n自动转换成 \n （注意：只能与 r 或 r+ 模式同使用）
- rU
- r+U
- rbU
- rb+U
"b"表示处理二进制文件（如：FTP发送上传ISO镜像文件，linux可忽略，windows处理二进制文件时需标注）
- rb
- wb
- ab
以下是file操作的源码解析：
1 class file(object):
2
3 def close(self): # real signature unknown; restored from __doc__
4 关闭文件
5
6 """close() -> None or (perhaps) an integer. Close the file.
7
8 Sets data attribute .closed to True. A closed file cannot be used for
9 further I/O operations. close() may be called more than once without
10 error. Some kinds of file objects (for example, opened by popen())
11 may return an exit status upon closing.
12 """
13
14 def fileno(self): # real signature unknown; restored from __doc__
15 文件描述符
16
17 """fileno() -> integer "file descriptor".
18
19 This is needed for lower-level file interfaces, such os.read(). """
20
21 return 0
22
23 def flush(self): # real signature unknown; restored from __doc__
24 刷新文件内部缓冲区
25
26 """ flush() -> None. Flush the internal I/O buffer. """
27
28 pass
29
30 def isatty(self): # real signature unknown; restored from __doc__
31 判断文件是否是同意tty设备
32
33 """ isatty() -> true or false. True if the file is connected to a tty device. """
34
35 return False
36
37 def next(self): # real signature unknown; restored from __doc__
38 获取下一行数据，不存在，则报错
39
40 """ x.next() -> the next value, or raise StopIteration """
41
42 pass
43
44
45
46 def read(self, size=None): # real signature unknown; restored from __doc__
47 读取指定字节数据
48
49 """read([size]) -> read at most size bytes, returned as a string.
50
51 If the size argument is negative or omitted, read until EOF is reached.
52 Notice that when in non-blocking mode, less data than what was requested
53 may be returned, even if no size parameter was given."""
54
55 pass
56
57 def readinto(self): # real signature unknown; restored from __doc__
58 读取到缓冲区，不要用，将被遗弃
59
60 """ readinto() -> Undocumented. Don't use this; it may go away. """
61
62 pass
63
64
65 def readline(self, size=None): # real signature unknown; restored from __doc__
66 仅读取一行数据
67 """readline([size]) -> next line from the file, as a string.
68
69 Retain newline. A non-negative size argument limits the maximum
70 number of bytes to return (an incomplete line may be returned then).
71 Return an empty string at EOF. """
72
73 pass
74
75 def readlines(self, size=None): # real signature unknown; restored from __doc__
76 读取所有数据，并根据换行保存值列表
77
78 """readlines([size]) -> list of strings, each a line from the file.
79
80 Call readline() repeatedly and return a list of the lines so read.
81 The optional size argument, if given, is an approximate bound on the
82 total number of bytes in the lines returned. """
83
84 return []
85
86
87
88 def seek(self, offset, whence=None): # real signature unknown; restored from __doc__
89 指定文件中指针位置
90 """seek(offset[, whence]) -> None. Move to new file position.
91
92 Argument offset is a byte count. Optional argument whence defaults to
93 0 (offset from start of file, offset should be >= 0); other values are 1
94 (move relative to current position, positive or negative), and 2 (move
95 relative to end of file, usually negative, although many platforms allow
96 seeking beyond the end of a file). If the file is opened in text mode,
97 only offsets returned by tell() are legal. Use of other offsets causes
98 undefined behavior.
99 Note that not all file objects are seekable. """
100
101 pass
102
103
104
105 def tell(self): # real signature unknown; restored from __doc__
106 获取当前指针位置
107
108 """ tell() -> current file position, an integer (may be a long integer). """
109 pass
110
111
112 def truncate(self, size=None): # real signature unknown; restored from __doc__
113 截断数据，仅保留指定之前数据
114
115 """ truncate([size]) -> None. Truncate the file to at most size bytes.
116
117 Size defaults to the current file position, as returned by tell().“""
118
119 pass
120
121