Working with C++ collections from Python package

This article provides an introduction to cross-technology handling of collections. Data structures are one of the essential aspects of every piece of software. Any application constantly process various information, that very often require specific grouping and access strategies. This aspect is addressed by arrays and more advanced collection types. By using the Javonet framework, users gain ability to easily and effectively work with data structures originating from Python package. Every collection from Python package is treated as reference.

Javonet allows you to reference and use modules or packages written in (Java/Kotlin/Groovy/Clojure, C#/VB.NET, Ruby, Perl, Python, JavaScript/TypeScript) like they were created in your technology. If have not yet created your first project check Javonet overview and quick start guides for your technology.

With Javonet you can interact with collections from Python package like they were available in C++ but invocation must be performed through Javonet SDK API.

Working with C++ lists from Python package

Javonet SDK contains various methods to interact with lists and consume the results in C++:

I code in:
// use Activate only once in your app
Javonet::Activate("your-license-key");

// create called runtime context
auto calledRuntime = Javonet::InMemory()->Python();

// get list from built-in types
auto typeList = calledRuntime->GetType("builtins.list")->Execute();

// create instance of list
auto list = typeList->CreateInstance()->Execute();

// invoke instance method
list->InvokeInstanceMethod("extend", std::vector<std::any>{ "one", "two", "three", "four", "five", "six" })->Execute();

// get elements from list
auto element0 = list->GetIndex(0)->Execute();
auto element1 = (*list)[1]->Execute();

auto result0 = std::any_cast<std::string>(element0->GetValue());
auto result1 = std::any_cast<std::string>(element1->GetValue());

// get size of list
auto size = std::any_cast<int>(list->GetSize()->Execute()->GetValue());

// write results to console
std::cout << result0 << std::endl;
std::cout << result1 << std::endl;
std::cout << size << std::endl;

In the snippet above, list specific to called technology framework is created.
Then, some elements are added to the list. Finally, this list can be handled through Javonet SDK, f.e. with getIndex method.

Working with C++ dictionary from Python package

Javonet SDK contains various methods to interact with dictionaries and consume the results in C++:

I code in:
// use Activate only once in your app
Javonet::Activate("your-license-key");

// create called runtime context
auto calledRuntime = Javonet::InMemory()->Python();

// get generic class 
auto typeDictionary = calledRuntime->GetType("builtins.dict")->Execute();

// create instance of generic class
auto dictionary = typeDictionary->CreateInstance()->Execute();

// set elements in dictionary
dictionary->SetIndex("pi", M_PI)->Execute();
dictionary->SetIndex("e", M_E)->Execute();
dictionary->SetIndex("c", 299792458.0)->Execute();

// get elements from dictionary
auto response1 = dictionary->GetIndex("c")->Execute();
auto response2 = (*dictionary)["e"]->Execute();

auto c_value = std::any_cast<double>(response1->GetValue());
auto e_value = std::any_cast<double>(response2->GetValue());

// write results to console
std::cout << c_value << std::endl;
std::cout << e_value << std::endl;

In the snippet above, list specific to called technology framework is created.
Then, some elements are added to the list. Finally, this list can be handled through Javonet SDK, f.e. with getIndex method.

The same operation can be performed remotely by just changing the new Runtime Context invocation from in memory to tcp that will create and interact with your Python package objects on any remote node, container or service that hosts Javonet Code Gateway. This way you can preserve the same logic in your application and instantly switch between monolithic and microservices architecture without the need to implement the integration layer based on web services or other remote invocation methods.

Read more about use cases and software architecture scenarios where Javonet runtime bridging technology can support your development process.

Additional references