This library provides the features to directly call and partially interoperate with Python from the Ruby language. You can import arbitrary Python modules into Ruby modules, call Python functions with automatic type conversion from Ruby to Python.
Supported Ruby versions
pycall.rb supports Ruby version 2.3 or higher.
Supported Python versions
pycall.rb supports Python version 2.7 or higher.
Note that in Python 2.7 old-style class, that is defined without a super class, is not fully supported in pycall.rb.
Note for pyenv users
pycall.rb requires Python's shared library (e.g.
libpython3.7m.so). pyenv does not build the shared library in default, so you need to specify
--enable-shared option at the installation like below:
$ env PYTHON_CONFIGURE_OPTS='--enable-shared' pyenv install 3.7.2
Add this line to your application's Gemfile:
And then execute:
Or install it yourself as:
$ gem install --pre pycall
Here is a simple example to call Python's
math.sin function and compare it to the
Math.sin in Ruby:
require 'pycall/import' include PyCall::Import pyimport :math math.sin(math.pi / 4) - Math.sin(Math::PI / 4) # => 0.0
Type conversions from Ruby to Python are automatically performed for numeric, boolean, string, arrays, and hashes.
Releasing the RubyVM GVL during Python function calls
You may want to release the RubyVM GVL when you call a Python function that takes very long runtime. PyCall provides
PyCall.without_gvl method for such purpose. When PyCall performs python function call, PyCall checks the current context, and then it releases the RubyVM GVL when the current context is in a
PyCall.without_gvl do # In this block, all Python function calls are performed without # the GVL acquisition. pyobj.long_running_function() end # Outside of PyCall.without_gvl block, # all Python function calls are performed with the GVL acquisition. pyobj.long_running_function()
Debugging python finder
When you encounter
PyCall::PythonNotFound error, you can investigate PyCall's python finder by setting
PYCALL_DEBUG_FIND_LIBPYTHON environment variable to
1. You can see the log like below:
$ PYCALL_DEBUG_FIND_LIBPYTHON=1 ruby -rpycall -ePyCall.builtins DEBUG(find_libpython) find_libpython(nil) DEBUG(find_libpython) investigate_python_config("python3") DEBUG(find_libpython) libs: ["Python.framework/Versions/3.7/Python", "Python", "libpython3.7m", "libpython3.7", "libpython"] DEBUG(find_libpython) libpaths: ["/opt/brew/opt/python/Frameworks/Python.framework/Versions/3.7/lib", "/opt/brew/opt/python/lib", "/opt/brew/opt/python/Frameworks", "/opt/brew/Cellar/python/3.7.2_1/Frameworks/Python.framework/Versions/3.7", "/opt/brew/Cellar/python/3.7.2_1/Frameworks/Python.framework/Versions/3.7/lib"] DEBUG(find_libpython) Unable to find /opt/brew/opt/python/Frameworks/Python.framework/Versions/3.7/lib/Python.framework/Versions/3.7/Python DEBUG(find_libpython) Unable to find /opt/brew/opt/python/Frameworks/Python.framework/Versions/3.7/lib/Python.framework/Versions/3.7/Python.dylib DEBUG(find_libpython) Unable to find /opt/brew/opt/python/Frameworks/Python.framework/Versions/3.7/lib/darwin/Python.framework/Versions/3.7/Python DEBUG(find_libpython) Unable to find /opt/brew/opt/python/Frameworks/Python.framework/Versions/3.7/lib/darwin/Python.framework/Versions/3.7/Python.dylib DEBUG(find_libpython) Unable to find /opt/brew/opt/python/lib/Python.framework/Versions/3.7/Python DEBUG(find_libpython) Unable to find /opt/brew/opt/python/lib/Python.framework/Versions/3.7/Python.dylib DEBUG(find_libpython) Unable to find /opt/brew/opt/python/lib/darwin/Python.framework/Versions/3.7/Python DEBUG(find_libpython) Unable to find /opt/brew/opt/python/lib/darwin/Python.framework/Versions/3.7/Python.dylib DEBUG(find_libpython) dlopen("/opt/brew/opt/python/Frameworks/Python.framework/Versions/3.7/Python") = #<Fiddle::Handle:0x00007fc012048650>
PyCall object system
PyCall wraps pointers of Python objects in
PyCall::PyPtr class has two subclasses,
PyCall::PyTypePtr is specialized for type (and classobj in 2.7) objects, and
PyCall::PyRubyPtr is for the objects that wraps pointers of Ruby objects.
PyCall::PyPtr objects are used mainly in PyCall infrastructure. Instead, we usually treats the instances of
Module, or other classes that are extended by
PyCall::PyObjectWrapper is a mix-in module for objects that wraps Python objects. A wrapper object should have
PyCall::PyPtr object in its instance variable
PyCall::PyObjectWrapper assumes the existance of
@__pyptr__, and provides general translation mechanisms between Ruby object system and Python object system. For example,
PyCall::PyObjectWrapper translates Ruby's coerce system into Python's swapped operation protocol.
Specifying the Python version
If you want to use a specific version of Python instead of the default, you can change the Python version by setting the
PYTHON environment variable to the path of the
After checking out the repo, run
bin/setup to install dependencies. Then, run
rake spec to run the tests. You can also run
bin/console for an interactive prompt that will allow you to experiment.
To install this gem onto your local machine, run
bundle exec rake install. To release a new version, update the version number in
version.rb, and then run
bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the
.gem file to rubygems.org.
Bug reports and pull requests are welcome on GitHub at https://github.com/mrkn/pycall.rb.
PyCall.jl is referred too many times to implement this library.
The gem is available as open source under the terms of the MIT License.