Why is My Text File Empty After My Python Script Runs?

You're writing a simple Python script to save some results or log some information to a .txt file. You use the open() function to create the file and the .write() method to add your text. The code seems straightforward, and most importantly, it runs without a single error.

Python

file_handle = open("my_log.txt", "w")
file_handle.write("Log Entry 1: Process started.")
file_handle.write("Log Entry 2: Data processing complete.")
# The script finishes here

You navigate to the folder, eager to see your my_log.txt file. You open it, but your heart sinks. It's completely empty. You run the script again. Still nothing. The code ran perfectly, so where did your data go?

This is a classic "ghost bug" that stumps nearly every new Python programmer. Your data isn't lost; it's just stuck in a temporary holding area, and you forgot the final, crucial step to make it permanent.

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The Problem: The Unfinished Shopping Trip (File Buffering)

To understand what's happening, let's use an analogy. Writing to a file is like a shopping trip.

1. open("file.txt", "w"): This is you grabbing a shopping cart when you enter the store.

2. file.write(...): This is you putting items into your cart. The items are with you, inside the store, but they aren't officially yours yet. To improve performance, your computer does the same thing. It "buffers" the data you write, collecting it in memory (the cart) instead of writing every small change to the disk immediately.

3. Forgetting file.close(): This is like leaving your full shopping cart in an aisle and walking out of the store. You never went through the checkout. The store's inventory system never officially recorded your purchase, and the items are eventually put back on the shelf. Similarly, if your script ends without properly closing the file, the operating system might discard the "buffered" data, and it will never be written to the disk.

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The Solution: Always Use with open() (The Pythonic Way)

While you could simply add file_handle.close() to the end of your script, there is a much safer, cleaner, and more modern way to handle files in Python: the with statement.

The with open(...) as ...: syntax creates a "context manager." This is a fancy term for a special block of code that guarantees a setup and a cleanup step.

When you use a with statement for file I/O:

1. It automatically opens the file for you.

2. It lets you run all your code in the indented block.

3. Crucially, it automatically and reliably closes the file for you the moment you exit the block—no matter what.

Even if your code crashes with an error inside the with block, Python guarantees the file will be closed properly, and your data will be saved.

The Correct, Modern Code:

Python

with open("my_log.txt", "w") as file:
    file.write("Log Entry 1: Process started.\n")
    file.write("Log Entry 2: Data processing complete.\n")

# No need for file.close()! It's handled for you.
# By the time the code gets here, my_log.txt is safely written and closed.
print("Log file has been created successfully.")

This is the universally recommended way to work with files in Python.

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Frequently Asked Questions (FAQs)

1. What does the "w" in open("file.txt", "w") mean?

This is the file "mode." The most common modes are:

• 'w' (Write): Opens the file for writing. Warning: It overwrites the file if it already exists.

• 'a' (Append): Opens the file for writing, but adds new data to the end of the file instead of overwriting it.

• 'r' (Read): Opens the file for reading only (this is the default).

2. Why is with open() safer than just using file.close()?

If you use file.close() manually and an error occurs in your code before that line is reached, your script will crash, and the close() method will never be called, potentially leading to data loss. The with statement guarantees the file is closed even if errors occur.

3. Do I need to use this for reading files too?

Yes. While the risk of data loss isn't there, it's a best practice to always use with open() for reading files as well. It ensures that your program properly releases the file resources back to the operating system.

Conclusion: Check Out Your Shopping Cart

The mystery of the empty file is solved by understanding file buffering. Your data wasn't gone; it was just waiting for you to complete the transaction.

By adopting the with open() pattern as your standard way of handling files, you ensure that your "shopping cart" is always checked out properly, your data is safely written to the disk, and your code is more robust and professional. It's a simple change that solves a frustrating problem and prevents future bugs. For more in-depth information, the official Python Tutorial on Reading and Writing Files is an excellent resource.