Luke Lee

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Resource allocation of Python tuples

I'm currently reading the early release of High Performance Python. The book is pretty rough around the edges since it's not even officially published. However, I have high hopes for the final product. There's already a lot of useful information in this early stage.

For example, did you know this about CPython tuples?

Another benefit of the static nature of tuples is something python does in the back‐ ground: resource caching. Python is garbage collected, which means that when a vari‐ able isn’t used anymore python frees the use of the memory back to the operating system for use in other applications (or other variables).

For tuples of sizes 1-20, when they are no longer used the space isn’t immediately given back to the system but rather saved for future use. This makes it so that when a new tuple of that size is needed in the future we don’t need to communicate with the operating system to find a region in memory to put the data since we have a reserve of free memory already.

That's neat, but the book didn't cite any proof. So, I did my own research in the source of Python 2.7.7. Sure enough, the book's authors were exactly right. The proof is right at the top of the tuple C implementation, and you can read the source to see the full extent of the optimization.

Published: 06-13-2014 20:53:02

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