This is a Pyston mirror, for NumPy support.

Pyston Build Status Gitter

Pyston is a performance-oriented Python implementation built using LLVM and modern JIT techniques. For a high-level description of how it works, please check out our technical overview or our FAQ for some more details.

We have a small website pyston.org, which for now just hosts the blog. We have two mailing lists: pyston-dev@ for development-related discussions, and pyston-announce@ which is for wider announcements (new releases, major project changes). We also have a gitter chat room where most discussion takes place.

Current state

Pyston should be considered in alpha: it "works" in that it can successfully run Python code, but it is still quite far from being useful for end-users.

Currently, Pyston targets Python 2.7, only runs on x86_64 platforms, and only has been tested on Ubuntu. Support for more platforms -- along with Python 3 compatibility -- is desired but deferred until we feel successful on our initial platform. Pyston does not currently work on Mac OSX, and it is not clear when it will.


Pyston welcomes any kind of contribution; please see CONTRIBUTING.md for details.

tl;dr: You will need to sign the Dropbox CLA and run the tests.

We have some documentation for those interested in contributing: see our Development Guide and development tips.


v0.5: Coming soon
  • Focus is on being ready to run Dropbox's production services. Initial plan:
    • Support for a final few esoteric Python features
    • Better stability and performance (but particularly for the Dropbox servers)
v0.4: released 11/3/2015
  • Many new features and better language support
    • Passes most of the tests of several famous python libraries
    • Unicode support
    • GC finalizer
    • much improved C API support
  • Better performance
    • Custom C++ exception handler
    • Object Cache (improves startup time)
    • Baseline JIT
v0.3: released 2/24/2015
  • Better language support
    • Can self-host all of our internal Python scripts
  • Better performance
    • Match CPython's performance on our small benchmark suite
v0.2: released 9/11/2014
  • Focus was on improving language compatibility to the point that we can start running "real code" in the form of existing benchmarks.
  • Many new features:
    • Exceptions
    • Class inheritance, metaclasses
    • Basic native C API support
    • Closures, generators, lambdas, generator expressions
    • Default arguments, keywords, *args, **kwargs
    • Longs, and integer promotion
    • Multithreading support
  • We have allowed performance to regress, sometimes considerably, but (hopefully) in places that allow for more efficient implementations as we have time.
v0.1: released 4/2/2014
  • Focus was on building and validating the core Python-to-LLVM JIT infrastructure.
  • Many core parts of the language were missing.

Trying it out

We have some build instructions at INSTALLING.md. If you have any issues, please feel free to file an issue in the issue tracker, or mention it via email or gitter.

Once you've followed those instructions, you should be able to do

$ make check

And see that hopefully all of the tests pass. (If they don't, please let us know.)

All pull requests are built and tested by travis-ci.org running Ubuntu 12.04. See travis-ci.org/dropbox/pyston/builds.

Running Pyston

Pyston builds in a few different configurations; right now there is pyston_dbg, which is the debug configuration and contains assertions and debug symbols, and pyston_release, the release configuration which has no assertions or debug symbols, and has full optimizations. You can build them by saying make pyston_dbg or make pyston_release, respectively. If you are interested in seeing how fast Pyston can go, you should try the release configuration, but there is a good chance that it will crash, in which case you can run the debug configuration to see what is happening.

There are a number of other configurations useful for development: "pyston_debug" contains full LLVM debug information, but will weigh in at a few hundred MB. "pyston_prof" contains gprof-style profiling instrumentation; gprof can't profile JIT'd code, reducing it's usefulness in this case, but the configuration has stuck around since it gets compiled with gcc, and can expose issues with the normal clang-based build.

You can get a simple REPL by simply typing make run; it is not very robust right now, and only supports single-line statements, but can give you an interactive view into how Pyston works. To get more functionality, you can do ./pyston_dbg -i [your_source_file.py], which will go into the REPL after executing the given file, letting you access all the variables you had defined.

Makefile targets

  • make pyston_release: to compile in release mode and generate the pyston_release executable
  • make check: run the tests
  • make run: run the REPL
  • make format: run clang-format over the codebase

For more, see development tips

Pyston command-line options:

Pyston-specific flags:

Set verbosity to 0
Increase verbosity by 1
Print out the internal stats at exit.
Disable the Pyston interpreter. This is mostly used for debugging, to force the use of higher compilation tiers in situations they wouldn't typically be used.
Force Pyston to always run at the highest compilation tier. This doesn't always produce the fastest running time due to the lack of type recording from lower compilation tiers, but similar to -n can help test the code generator.
Force always using the Pyston interpreter. This is mostly used for debugging / testing. (Takes precedence over -n and -O)
Use a stripped stdlib. When running pyston_dbg, the default is to use a stdlib with full debugging symbols enabled. Passing -r changes this behavior to load a slimmer, stripped stdlib.
Disable the pypa parser.
Standard Python flags:
Go into the repl after executing the given script.

There are also some lesser-used flags; see src/jit.cpp for more details.