Python file read and write mechanism

Python provides the necessary functions and methods for basic file operation by default

How to open the file:

Open (Name[,mode[buf]])

Name: File path

Mode: Open mode

BUF: Buffer buffering size

File read mode:

Read ([size]): Read file (read size byte, read all by default)

ReadLine ([size]): reads a row

ReadLine ([size]): Read buffer buf (IO. Default_set_buffer), returns the list of each row

ITER: Using an iterator to traverse the Read file F.open (name); iter_f = iter (f); Using the for line in Iter_f Loop iterator

File Write Method:

Write (str): Writes a string to a file

Writelines (sequence_of_strings): Writes multiple lines to a file, with arguments as objects that can be iterated

When write (str) is called, the Python interpreter calls the system call to write the contents to disk, but the Linux kernel has a file caching mechanism, so caches the kernel buffers, and when close () or flush () is called, the content is actually written to the file

or write -in data volume greater than or equal to write cache, write cache will also be synchronized to disk

Purpose of closing the file

1: Write cache sync to disk

The number of open files per process in the 2:linux system is limited

3: If the number of open files to the system limit, the open file will fail

Python file pointer operation:

Seek (Offset[,whence]) move the file pointer

Offset: Offsets, can be a negative number

Whence: Offset relative position

How the Python file pointer is positioned:

Os. Seek_set start position relative to the file 0

Os. Seek_cur relative to the current position of the file 1

Os. Seek_end position relative to end of file 2

Python file properties:

File.fileno (): File descriptor;

File.mode: File open permission;

File.encoding: File encoding method;

File.closed: Whether the file is closed;

Python Standard Files:

Standard input file: Sys.stdin; Read-only descriptor is 0

Standard output file: sys.stdout; Write-only descriptor is 1

Standard error file: Sys.stderr; Write-only descriptor is 2

Python command-line arguments:

The SYS module provides the SYS.ARGV property, which allows you to get command-line arguments. SYS.ARGV is a string sequence that holds the command-line arguments, where sys.argv[0] is the file name and 1~n is the true argument

Python File Encoding method

The default encoding format for Python files is ASCII format, to be written in Chinese you can convert the encoding format

1. A = Unicode.encode (U ' hello ', ' utf-8 ') conversion, a Chinese character occupies 3 bytes in ASCII code and 2 bytes in Unicode.

2. Create a file in utf-8 format directly. Create the specified encoding format file using the methods provided by the codecs module:

Codecs.open (fname, mode, encoding, errors, buffering): Open a file using the specified encoding format

3. You can also create a file in the specified encoding format using the system-provided open () function:

Open (file, mode= ' R ', Buffering=-1, Encoding=none, Errors=none, Newline=none, Closefd=true, Opener=none)

Simple Linux File system

Here is the process for Python action files

Reading these, is not the Python file mechanism has a certain understanding of the ^^!

Andy
Source: http://www.cnblogs.com/onepiece-andy/
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Python file read and write mechanism