How to close a file descriptor in Python
Overview
Everything is considered as a file in Linux. For example, files, directories, and sockets are all files.
Every file has a non-negative integer associated with it. This non-negative integer is called the file descriptor for that particular file. The file descriptors are allocated in sequential order with the lowest possible unallocated positive integer value taking precedence.
Whenever a program is run or executed, the following files are always opened:
- Standard input (
STDIN) with the file descriptor as0. - Standard output (
STDOUT) with the file descriptor as1. - Standard error (
STDERR) with the file descriptor as2.
The os module
The os library in Python provides functions that help us interact with the underlying operating system.
The close method of the os module
The close method of the os module is used to close the given file descriptor.
Note: Refer here to read more about how to close a range of file descriptors.
Syntax
os.close(fd)
fd is the file descriptor that needs to be closed.
Code example
Let’s look at the code below:
import osf_name = "file.txt"fileObject = open(f_name, "r")fd = fileObject.fileno()print("The file descriptor for %s is %s" % (f_name, fd))os.close(fd)
Code explanation
In the code above, we create a file called file.txt.
- Line 1: We import the
osmodule. - Line 3: We define a variable called
f_namethat holds the file name. - Line 4: We create a file object by using the
open()with the read mode (r). - Line 5: The file descriptor for the file is obtained using the
fileno()method. - Line 6: We print the file descriptor.
- Line 8: We close the file descriptor using the
os.close()method.
