Tweedledum
Tweedledum is a library for synthesis, compilation, and optimization of quantum circuits. The library is written to be scalable up to problem sizes in which quantum circuits outperform classical ones. Also, it is meant to be used both independently and alongside established tools.
Its design is guided by three mantras:
Gotta run fast: execution-time performance is a priority.
Your compiler, your rules. You know better. At least, Tweedledum hopes so! The library provides a standard set of operators that can be easily extended (thanks to some type-erasure black magic). However, the library will leave your operators completely alone if you don't write passes that specifically manipulate them. Furthermore, Tweedledum will rarely take any decision in your behalf, i.e., it does not provide generic methods to optimize or synthesize circuits, you need to specifically call the algorithms you want.