This number is typically in the thousands.

Operating systems limit the number of open files any single process can have.

Just like how you might use an ID field to get a record from a database, Python provides this number to the operating system every time it reads or writes from a file.

fileno() method on the opened file object will return the integer used by the operating system as a file descriptor. > with open ( 'test_file.txt', mode = 'w' ) as file. fileno() method that you can use to find the file handle: Whenever Python wants to read, write, or close the file, it’ll make another system call, providing the file handle number. Once you have the number associated with the file, you’re ready to do read or write operations. The operating system will then return an unsigned integer called a file handle on Windows and a file descriptor on UNIX-like systems, including Linux and macOS: A Python process making a system call and getting the integer 10 as the file handle When you open a file with open(), you make a system call to the operating system to locate that file on the hard drive and prepare it for reading or writing. The operating system is the mediator between processes, such as Python, and all the system resources, such as the hard drive, RAM, and CPU time. Python delegates file operations to the operating system. In Short: Files Are Resources Limited by the Operating System Free Download: Get a sample chapter from CPython Internals: Your Guide to the Python 3 Interpreter showing you how to unlock the inner workings of the Python language, compile the Python interpreter from source code, and participate in the development of CPython.

Close open files on server