Reading Text Files
Explore how to read text files in Python with best practices that ensure safety, efficiency, and portability. Learn to use context managers, handle errors like missing files, read large files line by line to conserve memory, and specify UTF-8 encoding to avoid decoding issues. This lesson equips you to work reliably with text data across different operating systems.
Most real-world applications need to store and retrieve data from persistent storage. Common tasks such as loading configuration files, parsing logs, or processing large datasets require programs to interact with the file system. File operations depend on external conditions that the program cannot fully control. A file might be missing, permissions may prevent access, or the text encoding may differ between operating systems. To handle these situations reliably, we need structured error handling and careful file management.
In this lesson, we will learn the idiomatic Python techniques for reading files that prioritize safety, portability, and performance.
The open function
To access a file, we use the built-in function open(). This function opens a file on disk and returns a file object (often called a handle). The returned object provides methods for reading from and writing to the file.
We must specify a mode when opening a file. The most common mode is 'r' (read), which is the default. If the file does not exist, trying to open it in read mode will crash the program with a FileNotFoundError.
While we could strictly use open() and close(), Python provides a safer syntax: the with statement. This context manager automatically closes the file as soon as we exit ...