POLYGLOT.md

Interop

Interop from Python

You can import the polyglot module to interact with other languages.

import polyglot

You can import a global value from the entire polyglot scope:

imported_polyglot_global = polyglot.import_value("global_name")

This global should then work as expected; accessing attributes assumes it reads from the members namespace; accessing items is supported both with strings and numbers; calling methods on the result tries to do a straight invoke and falls back to reading the member and trying to execute it.

You can evaluate some code in another language:

polyglot.eval(string="1 + 1", language="ruby")

It also works with the path to a file:

polyglot.eval(path="./my_ruby_file.rb", language="ruby")

If you pass a file, you can also try to rely on the file-based language detection:

polyglot.eval(path="./my_ruby_file.rb")

To export something from Python to other Polyglot languages so they can import it:

foo = object()
polyglot.export_value(foo, name="python_foo")

The export function can be used as a decorator, in this case the function name is used as the globally exported name:

@polyglot.export_value
def python_method():
    return "Hello from Python!"

Finally, to interoperate with Java (only when running on the JVM), you can use the java module:

import java
BigInteger = java.type("java.math.BigInteger")
myBigInt = BigInteger(42)
myBigInt.shiftLeft(128)            # public Java methods can just be called
myBigInt["not"]()                  # Java method names that are keywords in
                                   # Python can be accessed using "[]"
byteArray = myBigInt.toByteArray()
print(list(byteArray))             # Java arrays can act like Python lists

For packages under the java package, you can also use the normal Python import syntax:

import java.util.ArrayList
from java.util import ArrayList

# these are the same class
java.util.ArrayList == ArrayList

al = ArrayList()
al.add(1)
al.add(12)
print(al) # prints [1, 12]

In addition to the type builtin method, the java module, exposes the following methods as well:

Builtin	Specification
instanceof(obj, class)	returns True if obj is an instance of class (class must be a foreign object class)
is_function(obj)	returns True if obj is a Java host language function wrapped using Truffle interop
is_object(obj)	returns True if obj if the argument is Java host language object wrapped using Truffle interop
is_symbol(obj)	returns True if obj if the argument is a Java host symbol, representing the constructor and static members of a Java class, as obtained by java.type

import java
ArrayList = java.type('java.util.ArrayList')
my_list = ArrayList()
print(java.is_symbol(ArrayList))    # prints True
print(java.is_symbol(my_list))      # prints False, my_list is not a Java host symbol
print(java.is_object(ArrayList))    # prints True, symbols are also host objects
print(java.is_function(my_list.add))# prints True, the add method of ArrayList
print(java.instanceof(my_list, ArrayList)) # prints True