Why Is It Important to Close Files in Python?

At some point in your Python coding journey, you learn that you should use a context manager to open files. Python context managers make it easy to close your files once you’re done with them:

with open("hello.txt", mode="w") as file:
    file.write("Hello, World!")

The with statement initiates a context manager. In this example, the context manager opens the file hello.txt and manages the file resource as long as the context is active. In general, all the code in the indented block depends on the file object being open. Once the indented block either ends or raises an exception, then the file will close.

If you’re not using a context manager or you’re working in a different language, then you might explicitly close files with the try … finally approach:

try:
    file = open("hello.txt", mode="w")
    file.write("Hello, World!")
finally:
    file.close()

The finally block that closes the file runs unconditionally, whether the try block succeeds or fails. While this syntax effectively closes the file, the Python context manager offers less verbose and more intuitive syntax. Additionally, it’s a bit more flexible than simply wrapping your code with try … finally.

You probably use context managers to manage files already, but have you ever wondered why most tutorials and four out of five dentists recommend doing this? In short, why is it important to close files in Python?

In this tutorial, you’ll dive into that very question. First, you’ll learn about how file handles are a limited resource. Then you’ll experiment with the consequences of not closing your files.