对文件操作流程
- 打开文件,得到文件句柄并赋值给一个变量
- 通过句柄对文件进行操作
- 关闭文件
基本操作
1.f
=
open
(
'lyrics'
)
#打开文
2.first_line
=
f.readline()
3.print
(
'first line:'
,first_line)
#读一行
4.print
(
'我是分隔线'
.center(
50
,
'-'
))
5.data
=
f.read()
# 读取剩下的所有内容,文件大时不要用
6.print
(data)
#打印文件
7.f.close()
#关闭文件
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+,写读
- a+,同a
"U"表示在读取时,可以将 自动转换成 (与 r 或 r+ 模式同使用)
- rU
- r+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
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
def close(self): # real signature unknown; restored from __doc__ """ Close the file. A closed file cannot be used for further I/O operations. close() may be called more than once without error.#关闭的文件不能用于进一步的I/O操作。()可以被称为一次以上无误。 """ pass def fileno(self, *args, **kwargs): # real signature unknown """ Return the underlying file descriptor (an integer). """#返回文件描述符(一个整数) pass def isatty(self, *args, **kwargs): # real signature unknown """ True if the file is connected to a TTY device. """ pass def read(self, size=-1): # known case of _io.FileIO.read """ 注意,不一定能全读回来 Read at most size bytes, returned as bytes. Only makes one system call, so less data may be returned than requested. In non-blocking mode, returns None if no data is available. Return an empty bytes object at EOF. """ return "" def readable(self, *args, **kwargs): # real signature unknown """ True if file was opened in a read mode. """ pass def readall(self, *args, **kwargs): # real signature unknown """ Read all data from the file, returned as bytes. In non-blocking mode, returns as much as is immediately available, or None if no data is available. Return an empty bytes object at EOF. #从文件中读取所有数据,作为字节返回。 #在非阻塞模式下,返回的值与当前可用的一样多, #或无,如果没有可用的数据。在EOF中返回空字节对象。 """ pass def readinto(self): # real signature unknown; restored from __doc__ """ Same as RawIOBase.readinto(). """ pass #不要用,没人知道它是干嘛用的 def seek(self, *args, **kwargs): # real signature unknown """ Move to new file position and return the file position.#移动到新文件位置并返回文件位置。 Argument offset is a byte count. Optional argument whence defaults to SEEK_SET or 0 (offset from start of file, offset should be >= 0); other values are SEEK_CUR or 1 (move relative to current position, positive or negative), and SEEK_END or 2 (move relative to end of file, usually negative, although many platforms allow seeking beyond the end of a file). Note that not all file objects are seekable. """ pass def seekable(self, *args, **kwargs): # real signature unknown """ True if file supports random-access. """ pass def tell(self, *args, **kwargs): # real signature unknown """ Current file position.#当前文件位置 Can raise OSError for non seekable files. """ pass def truncate(self, *args, **kwargs): # real signature unknown """ Truncate the file to at most size bytes and return the truncated size.#将文件截断到最多大小的字节并返回截断的大小。 Size defaults to the current file position, as returned by tell(). The current file position is changed to the value of size. """ pass def writable(self, *args, **kwargs): # real signature unknown """ True if file was opened in a write mode. """ pass def write(self, *args, **kwargs): # real signature unknown """ Write bytes b to file, return number written. Only makes one system call, so not all of the data may be written. The number of bytes actually written is returned. In non-blocking mode, returns None if the write would block. """ pass
with语句
为了避免打开文件后忘记关闭,可以通过管理上下文,即:
with open('log','r') as f: pass
如此方式,当with代码块执行完毕时,内部会自动关闭并释放文件资源。
在Python 2.7 后,with又支持同时对多个文件的上下文进行管理,即:
with open('log1') as obj1, open('log2') as obj2: pass