What does python fd mean?

What does python fd mean?

In Python, you can read and write files through coding. However, it must be clear that the program's file reading and writing functions are actually provided by the operating system, because ordinary programs cannot directly operate them. disk.

When performing a file operation, Python will request the operating system to open an object—this object is usually called a file descriptor (fd for short), which corresponds to the file object to be operated later— —Then read and write data to the file object through the interface provided by the operating system, which is commonly known as "reading files" and "writing files".

The operation steps for file reading and writing are basically as follows:

1. Open the file-get the file descriptor.
2. Read and write files - operate file descriptors.
3. Close file - close the file descriptor.

In other words, the program's various operations on files actually refer to the file descriptors returned by the system.

In Python, the open() function is used to request the operating system to return a file object, and then other methods can be used to read and write data on the file object and other operations.

The open() function is used to return a file object (File Object), most commonly used with these two parameters: open(filename, mode). For example:

>>> f = open('sample.txt', 'w')

The first parameter filename is a string used to specify the name of the file to be opened, and the path can also be specified. If you do not specify the path where the file is located, Python will look for the file in the current folder and open it. If the file cannot be opened, an OSError exception will be thrown.

The file object is a path-like object in Python (can be translated as a class path object, or can be understood directly in English without translation), that is, an object that represents the system path of a file. It provides the path name of a file to be opened, which can be an absolute path or a path relative to the current working folder, or it provides a file descriptor to be encapsulated.

The system kernel (kernel) uses file descriptors (fd for short) to access files. That is to say, when actually using the open() function to open an existing file, the kernel returns a file description. symbol. When reading and writing files, you also need to use a file descriptor to specify the file to be read and written. The file descriptor is a non-negative integer in form, but is actually an index value.

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