500× faster: Four different ways to speed up your code

A Python function for counting letter frequencies in a book is optimized using multiple performance practices. The initial implementation is improved through efficiency measures like reducing redundant calculations and using appropriate data structures. Switching to Rust for compilation yields further speed gains. Parallelism is then applied to utilize multiple CPU cores. Through these combined practices, the final version achieves a 500x speedup compared to the original. The importance of proper measurement and testing throughout the optimization process is emphasized.