Скачать или смотреть Resolving Python's Compressed file ended before end-of-stream Error with LZMA Files

Learn how to troubleshoot and fix the `Compressed file ended before end-of-stream` error in Python when working with LZMA compressed files.
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Resolving Python's Compressed file ended before end-of-stream Error with LZMA Files

When working with compressed files in Python, you may come across the frustrating error: Compressed file ended before the end-of-stream marker was reached. This can be particularly perplexing when the file you are attempting to access works perfectly when extracted manually using tools like 7-Zip.

In this guide, we will explore common pitfalls that can lead to this error and how to fix them effectively, ensuring that you can handle LZMA files smoothly in your Python projects.

Understanding the Problem

The core issue arises when you attempt to read a compressed file after writing to it without properly closing the file. When a file is opened and modified but not closed, the data may still reside in user mode buffers, making it invisible to other processes or code segments. This lack of visibility can cause problems when you try to extract or read files, leading to the error mentioned above.

The user in our example tried to download an LZMA file and decompress it via Python but ran into issues. Specifically, they faced two approaches:

Using the built-in lzma library

Using the py7zr library

Both resulted in errors due to file handling mistakes. Let’s look into how to fix these issues.

Solution: Properly Handling Files in Python

Always Close Files

The very first step in avoiding errors when dealing with files is to ensure they are closed properly after operations. In Python, using close() is essential, but it is more efficient and safer to use a with statement that automatically handles opening and closing files.

Here's how you can adjust your file download code:

[[See Video to Reveal this Text or Code Snippet]]

Key Points:

Use with Statements: This ensures that files are closed promptly, even if an error occurs during processing.

Use Raw Strings for Windows Paths: Prefixing the path with r allows you to avoid issues with escape characters.

Reworking the Decompression

When it comes to decompressing the LZMA file, ensure that you correctly handle the reading of the file. For instance, ensure that you are using the readline() function correctly, as shown below:

[[See Video to Reveal this Text or Code Snippet]]

Avoiding Common Mistakes

Ensure you call readline() with parentheses to execute the function.

Make sure you are not introducing any unwanted data by skipping necessary file bytes that can break decompression.

Fixing the Use of py7zr

If you opt to use the py7zr library, make sure you are opening the file in the correct mode. If you intend to read from the archive, you should open it in read mode ('r'):

[[See Video to Reveal this Text or Code Snippet]]

Final Thoughts

By ensuring that you properly manage file closing and access modes, you can avoid the common pitfalls that lead to the cryptic LZMA error messages in Python. Proper file handling is crucial not just for reading but also for writing data to avoid data loss or corruption.

With these changes, you should be able to work with LZMA compressed files without any issues. Happy coding!