Python for DevOps

Chapter 2. Automating Files and the Filesystem

One of Python’s most powerful features is its ability to manipulate text and files. In the DevOps world, you are continually parsing, searching, and changing the text in files, whether you’re searching application logs or propagating configuration files. Files are a means of persisting the state of your data, code, and configuration; they are how you look back at what happened in logs and how you control what happens with configuration. With Python, you can create, read, and change files and text in the code that you can use repeatedly. Automating these tasks is indeed one aspect of modern DevOps that separates it from traditional system administration. Rather than keeping a set of instructions that you have to follow manually, you can write code. This diminishes your chances of missing steps or doing them out of order. If you are confident that your system uses the same steps every time you run it, you can have greater understanding and confidence in the process.

Reading and Writing Files

You can use the open function to create a file object that can read and write files. It takes two arguments, the path of the file and the mode (mode optionally defaults to reading). You use the mode to indicate, among other things, if you want to read or write a file and if it is text or binary data. You can open a text file using the mode r to read its contents. The file object has a read method that returns the contents of the file as a string: ...