Python: Text Input/Output Fundamentals
2026-02-21 23:42 Diff
https://hexlet.io/courses/python-io/lessons/about/theory_unit

Every programmer constantly encounters the need to read something from a file and write something to a file. At first glance, files may seem so simple!

A bit of theory

Modern operating systems have complex file input/output structures. Most operating systems do not allow programs to work directly with the disk to ensure maximum efficiency of file reading and writing and to control the security of this process. They cannot do it physically: one program cannot include an understanding of all the file systems — ways of storing data in files on a disk.

In addition to supporting different file systems, a modern operating system also deals with caching disk operations, checking access rights, and other administrative tasks.

The operating system provides specific objects for programs — file descriptors. With a file descriptor, you can write and read data without worrying about the file system, caching, and other low-level entities.

And here lies the catch: file descriptors are convenient, but creating each one consumes many resources.

Therefore, the operating system has a limit on the number of file descriptors used simultaneously. Moreover, each program is additionally restricted — it has its limit. When a program exhausts the available descriptors, the next attempt to open another file will result in an error. So programmers keep track of how many files the program opened at any given time and whether it closed them promptly.

Monitoring file closure is essential because simultaneous work on the same file can lead to unpredictable results. Moreover, improperly closed files can be saved incorrectly to the disk, resulting in data loss.

No need to panic

The above description may frighten someone with its complexity. However, Python is a modern programming language. It allows you to avoid many problems that arise when working with files. In this course, you will learn how to work with text files. However, you will learn to apply the essential techniques and tools to files with any content.

How to prepare for this course

Before taking this course, it is worth reviewing the basics of the language and refreshing your skills in working with collections:

You can find the correct sequence of courses in the Python Developer.