grumpy README

The project's README from github.com/google/grumpy. As one markdown file: README.md.

Grumpy: Go running Python

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Overview

Grumpy is a Python to Go source code transcompiler and runtime that is intended to be a near drop-in replacement for CPython 2.7. The key difference is that it compiles Python source code to Go source code which is then compiled to native code, rather than to bytecode. This means that Grumpy has no VM. The compiled Go source code is a series of calls to the Grumpy runtime, a Go library serving a similar purpose to the Python C API (although the API is incompatible with CPython's).

Limitations

Things that will probably never be supported by Grumpy

  1. exec, eval and compile: These dynamic features of CPython are not supported by Grumpy because Grumpy modules consist of statically-compiled Go code. Supporting dynamic execution would require bundling Grumpy programs with the compilation toolchain, which would be unwieldy and impractically slow.

  2. C extension modules: Grumpy has a different API and object layout than CPython and so supporting C extensions would be difficult. In principle it's possible to support them via an API bridge layer like the one that JyNI provides for Jython, but it would be hard to maintain and would add significant overhead when calling into and out of extension modules.

Things that Grumpy will support but doesn't yet

There are three basic categories of incomplete functionality:

  1. Language features: Most language features are implemented with the notable exception of old-style classes. There are also a handful of operators that aren't yet supported.

  2. Builtin functions and types: There are a number of missing functions and types in __builtins__ that have not yet been implemented. There are also a lot of methods on builtin types that are missing.

  3. Standard library: The Python standard library is very large and much of it is pure Python, so as the language features and builtins get filled out, many modules will just work. But there are also a number of libraries in CPython that are C extension modules which will need to be rewritten.

  4. C locale support: Go doesn't support locales in the same way that C does. As such, some functionality that is locale-dependent may not currently work the same as in CPython.

Running Grumpy Programs

Method 1: make run:

The simplest way to execute a Grumpy program is to use make run, which wraps a shell script called grumprun that takes Python code on stdin and builds and runs the code under Grumpy. All of the commands below are assumed to be run from the root directory of the Grumpy source code distribution:

echo "print 'hello, world'" | make run

Method 2: grumpc and grumprun:

For more complicated programs, you'll want to compile your Python source code to Go using grumpc (the Grumpy compiler) and then build the Go code using go build. Since Grumpy programs are statically linked, all the modules in a program must be findable by the Grumpy toolchain on the GOPATH. Grumpy looks for Go packages corresponding to Python modules in the __python__ subdirectory of the GOPATH. By convention, this subdirectory is also used for staging Python source code, making it similar to the PYTHONPATH.

The first step is to set up the shell so that the Grumpy toolchain and libraries can be found. From the root directory of the Grumpy source distribution run:

make
export PATH=$PWD/build/bin:$PATH
export GOPATH=$PWD/build
export PYTHONPATH=$PWD/build/lib/python2.7/site-packages

You will know things are working if you see the expected output from this command:

echo 'import sys; print sys.version' | grumprun

Next, we will write our simple Python module into the __python__ directory:

echo 'def hello(): print "hello, world"' > $GOPATH/src/__python__/hello.py

To build a Go package from our Python script, run the following:

mkdir -p $GOPATH/src/__python__/hello
grumpc -modname=hello $GOPATH/src/__python__/hello.py > \
    $GOPATH/src/__python__/hello/module.go

You should now be able to build a Go program that imports the package "__python__/hello". We can also import this module into Python programs that are built using grumprun:

echo 'from hello import hello; hello()' | grumprun

grumprun is doing a few things under the hood here:

  1. Compiles the given Python code to a dummy Go package, the same way we produced __python__/hello/module.go above
  2. Produces a main Go package that imports the Go package from step 1. and executes it as our __main__ Python package
  3. Executes go run on the main package generated in step 2.

Developing Grumpy

There are three main components and depending on what kind of feature you're writing, you may need to change one or more of these.

grumpc

Grumpy converts Python programs into Go programs and grumpc is the tool responsible for parsing Python code and generating Go code from it. grumpc is written in Python and uses the pythonparser module to accomplish parsing.

The grumpc script itself lives at tools/grumpc. It is supported by a number of Python modules in the compiler subdir.

Grumpy Runtime

The Go code generated by grumpc performs operations on data structures that represent Python objects in running Grumpy programs. These data structures and operations are defined in the grumpy Go library (source is in the runtime subdir of the source distribution). This runtime is analogous to the Python C API and many of the structures and operations defined by grumpy have counterparts in CPython.

Grumpy Standard Library

Much of the Python standard library is written in Python and thus "just works" in Grumpy. These parts of the standard library are copied from CPython 2.7 (possibly with light modifications). For licensing reasons, these files are kept in the third_party subdir.

The parts of the standard library that cannot be written in pure Python, e.g. file and directory operations, are kept in the lib subdir. In CPython these kinds of modules are written as C extensions. In Grumpy they are written in Python but they use native Go extensions to access facilities not otherwise available in Python.

Source Code Overview

Contact

Questions? Comments? Drop us a line at [email protected] or join our Gitter channel

grumpy (google/grumpy)

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10.5K ·GitHub
Grumpy
archived
What is this?Grumpy is Google's Python to Go transcompiler and runtime — a near drop-in replacement for CPython 2.7 that turns Python programs into native executables via generated Go source code.
How is it different from just running Python normally?There is no VM: instead of bytecode, your code becomes statically compiled Go that calls into the Grumpy runtime, a Go library serving a purpose similar to the Python C API, though the API is incompatible with CPython's.
How do I run a Python script with it?From the root of the Grumpy source distribution, run make run — it feeds Python code from stdin through the grumprun script, which builds and executes it under Grumpy.
What do I need to have installed before I can use it?The Go toolchain and the Grumpy source itself: beyond quick tests you compile Python to Go with grumpc and build it with go build, and grumpc is written in Python, so a Python interpreter is needed too.
Which Python features are missing or unsupported?It targets CPython 2.7 only. exec, eval and compile will never be supported and C extension modules cannot be loaded; many builtins, methods and standard library modules are still missing.
What does the generated Go code look like?It is a series of calls into the Grumpy runtime library — the generated Go source manipulates data structures representing Python objects, mirroring how CPython's C API works.
How does the Python standard library work without a VM?Pure-Python modules copied from CPython 2.7, PyPy and the Ouroboros project just work. Modules that need native facilities, like file and directory operations, are written in Python backed by Go extensions.
Can I compile my own modules and reuse them across programs?Yes — grumpc produces Go packages in the python subdirectory of your GOPATH, and because Grumpy programs are statically linked, every module a program uses must be findable there at build time.
Is Grumpy still being developed?No. The GitHub repository has been archived and is read-only, so development has stopped — weigh that before investing time in the toolchain.
What are similar projects?cython, tsx, zig, gopherjs, scriptc, closure-compiler, wire, porffor
Which topics is it in?transpiler, makefile, runtime, code-generation, google, compiler, programming, deprecated, go, command-line-tool, tool, apache-2.0
Creator
google
Size
1.4 MB
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10.5K
Updated
CommitNov 22
Age
9y
Commits · 90 Days