README.md in pycall-1.3.1 vs README.md in pycall-1.4.0
- old
+ new
@@ -4,21 +4,20 @@
</div>
# PyCall: Calling Python functions from the Ruby language
[](https://github.com/mrkn/pycall.rb/actions?query=workflow%3ACI)
-[](https://travis-ci.org/mrkn/pycall.rb)
[](https://ci.appveyor.com/project/mrkn/pycall-rb/branch/master)
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.
+pycall.rb supports Ruby version 2.4 or higher.
## Supported Python versions
pycall.rb supports Python version 2.7 or higher.
@@ -31,10 +30,16 @@
```
$ env PYTHON_CONFIGURE_OPTS='--enable-shared' pyenv install 3.7.2
```
+## Note for Windows users
+
+Currently, pycall.rb does not support Windows. Please try to use pycall.rb on WSL2 environment.
+
+On Windows, the error "[BUG] object allocation during garbage collection phase" is occurred at unpredictable timings.
+
## Installation
Add this line to your application's Gemfile:
```ruby
@@ -60,10 +65,37 @@
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.
+### Calling a constructor
+
+In Python, we call the constructor of a class by `classname(x, y, z)` syntax. Pycall.rb maps this syntax to `classname.new(x, y, z)`.
+
+### Calling a callable object
+
+In Python, we can call the callable object by `obj(x, y, z)` syntax. PyCall.rb maps this syntax to `obj.(x, y, z)`.
+
+### Passing keyword arguments
+
+In Python, we can pass keyword arguments by `func(x=1, y=2, z=3)` syntax. In pycallrb, we should rewrite `x=1` to `x: 1`.
+
+### The callable attribute of an object
+
+Pycall.rb maps the callable attribute of an object to the instance method of the corresponding wrapper object. So, we can write a Python expression `obj.meth(x, y, z=1)` as `obj.meth(x, y, z: 1)` in Ruby. This mapping allows us to call these attributes naturally as Ruby's manner.
+
+But, unfortunately, this mapping prohibits us to get the callable attributes. We need to write `PyCall.getattr(obj, :meth)` in Ruby to get `obj.meth` object while we can write `obj.meth` in Python.
+
+### 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 `python` executable.
+
+When `PYTHON` is not specified, pycall.rb tries to use `python3` first,
+and then tries to use `python`.
+
### 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`'s block.
@@ -99,10 +131,24 @@
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>
```
+## Special notes for specific libraries
+
+### matplotlib
+
+Use [mrkn/matplotlib.rb](https://github.com/mrkn/matplotlib.rb) instead of just importing it by `PyCall.import_module("matplotlib")`.
+
+### numpy
+
+Use [mrkn/numpy.rb](https://github.com/mrkn/numpy.rb) instead of just importing it by `PyCall.import_module("numpy")`.
+
+### pandas
+
+Use [mrkn/pandas.rb](https://github.com/mrkn/pandas.rb) instead of just importing it by `PyCall.import_module("pandas")`.
+
## PyCall object system
PyCall wraps pointers of Python objects in `PyCall::PyPtr` objects.
`PyCall::PyPtr` class has two subclasses, `PyCall::PyTypePtr` and
`PyCall::PyRubyPtr`. `PyCall::PyTypePtr` is specialized for type (and classobj
@@ -118,14 +164,74 @@
variable `@__pyptr__`. `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
+## Deploying on Heroku
-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 `python` executable.
+Heroku's default version of Python is not compiled with the `--enabled-shared`
+option and can't be accessed by PyCall. Alternative [buildpacks](https://devcenter.heroku.com/articles/buildpacks) are available,
+including these that have been reported to work with PyCall:
+
+https://github.com/richgong/heroku-buildpack-python
+https://github.com/dsounded/heroku-buildpack-python
+https://github.com/ReforgeHQ/heroku-buildpack-python
+
+These community-developed buildpacks are not supported by Heroku, so it's
+worth examining the source to make sure the buildpack you use suits your
+needs. For instance, 'ReforgeHQ' works well with Python 3.8.1, but has not
+been configured to work with other versions and may not be as generally
+useful as the 'dsounded' or 'richgong' buildpacks.
+
+The buildpack will expect to find both a `runtime.txt` and a `requirements.txt`
+file in the root of your project. You will need to add these to specify the
+version of Python and any packages to be installed via `pip`, _e.g_ to use
+version Python 3.8.1 and version 2.5 of the 'networkx' package:
+
+ $ echo "python-3.8.1" >> runtime.txt
+ $ echo "networkx==2.5" >> requirements.txt
+
+Commit these two files into project's repository. You'll use these to manage
+your Python environment in much the same way you use the `Gemfile` to manage
+Ruby.
+
+Heroku normally detects which buildpacks to use, but you will want to override
+this behavior. It's probably best to clear out existing buildpacks and specify
+exactly which buildpacks from scratch.
+
+First, take stock of your existing buildpacks:
+
+ $ heroku buildpack [-a YOUR_APP_NAME]
+
+For a Ruby/Rails application this will typically report the stock `heroku/ruby`
+buildpack, or possibly both `heroku/ruby` and `heroku/nodejs`.
+
+Clear the list and progressively add back your buildpacks, starting with the Python
+community-developed buildpack. For example, if `ruby` and `nodejs` buildpacks were
+previously installed, and chosing the 'ReforgeHQ' buildback, your setup process will
+be similar to this:
+
+ $ heroku buildpacks:clear
+ $ heroku buildpacks:add https://github.com/ReforgeHQ/heroku-buildpack-python -i 1
+ $ heroku buildpacks:add heroku/nodejs -i 2
+ # heroku buildpacks:add heroku/ruby -i 3
+
+If you have multiple applications on Heroku you will need to append each of these
+with application's identifier (_e.g._ `heroku buildpacks:clear -a YOUR_APP_NAME`).
+
+With each buildpack we are registering its index (the `-i` switch) in order to
+specify the order Heroku will load runtimes and execute bootstrapping code. It's
+important for the Python environment to be engaged first, as PyCall will need to
+be able to find it when Ruby-based processes start.
+
+Once you have set up your buildpacks, and have commited both `requirements.txt` and
+`runtime.txt` files to git, deploy your Heroku application as your normally would.
+The Python bootstrapping process will appear in the log first, followed by the Ruby
+and so on. PyCall should now be able to successfully call Python functions from
+within the Heroku environment.
+
+NB It is also possible to specify buildpacks within Docker images on Heroku.
+See Heroku's [documentation on using Docker Images](https://devcenter.heroku.com/articles/build-docker-images-heroku-yml).
## Development
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`