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Learn how to efficiently copy files from one directory to another in Python 3, ensuring that only new files are transferred, avoiding duplicates in the destination folder.
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This video is based on the question https://stackoverflow.com/q/64164861/ asked by the user 'UnarmedElk' ( https://stackoverflow.com/u/13333745/ ) and on the answer https://stackoverflow.com/a/64164939/ provided by the user 'Daniel Walker' ( https://stackoverflow.com/u/8075540/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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How to Copy Files if They Don't Exist in the Destination Folder Using Python 3

When working with files in Python, there are times when you need to transfer files from one location to another without creating duplicates. Suppose you work with a collection of PDFs and want to consolidate them into one folder for easier access. However, frequent copying can lead to frustration when the same files keep getting copied over, even when they already exist in the destination. In this post, we will explore a solution to copy files while ensuring that files already present in the destination are not duplicated.

The Problem

You might find yourself in a scenario where:

You have a source folder containing multiple subfolders with files you need to move.

Your goal is to copy only the files that do not already exist in the destination folder.

This process can become complicated without the right checks in place. Let’s take a look at a sample code to better understand the issue:

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

Despite having a check for existing files, the code may end up copying files that already exist. This is due to incorrect usage of the os.path.exists and os.walk functions.

The Solution

To address the problem effectively, we need to modify the code. Let's break down the updated approach:

Understanding Key Functions

os.path.exists: This function returns a Boolean indicating whether the specified path exists.

os.walk: This generates a directory tree and can output tuples containing the directory path, subdirectories, and files.

Updated Code Structure

With the understanding of these functions, here’s an updated version of the code that performs the desired file copying operation correctly:

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

Key Improvements

Correct File Check: The code now checks if the file is present in the list of files returned by os.listdir(dest_folder). This ensures that we are only copying files that are truly absent in the destination.

Simplified Logic: The previous redundancies are eliminated, making the logic straightforward and efficient.

Conclusion

With these adjustments, you can effectively copy files from a source directory to a destination directory while avoiding duplicates. This approach simplifies file management in Python and ensures seamless workflow, especially when handling large batches of files.

Now you can focus on what truly matters—organizing your PDFs without worrying about unnecessary duplicates. Happy coding!