Use Python package enum type in Perl app

This article provides an introduction to cross-technology handling of enum type. In programming, an enum (short for enumeration) type is a special data type that enables for a variable to be a set of predefined constants. The variable must be equal to one of the values that have been predefined for it. Enums are used to create our own data types, just like classes. They are particularly useful when we want to represent a fixed set of constants, such as days of the week, states, colors, directions, and more. This makes the code more readable and less prone to errors.

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 enum types from Python package as if they were available in Perl, but interaction must be performed through the Javonet SDK API. This allows you to handle and manipulate enum values, pass them to methods, and return them from methods, all while maintaining the type safety and readability of your Perl code.

Custom Python package with enum type

With Javonet it is possible to reference any custom Python package and interact with its methods declared on types defined within that module almost the same as with any other Perl library.

Snippet below represents the sample code from Python package which contains enum type.

import threading
import time

class TestClass:
    def __init__(self, public_value, private_value):
        self.public_value = public_value
        self.private_value = private_value
        

    from enum import Enum
    class Fruit(Enum):
        Apple = 1
        Banana = 2
        Orange = 3
        Mango = 4
    
    Fruits = []
    
    @staticmethod
    def add_fruits_to_list(fruits):
        TestClass.Fruits.extend(fruits)
        return "{0} fruits on the list".format(len(TestClass.Fruits))
from enum import Enum
class Fruit(Enum):
    Apple = 1
    Banana = 2
    Orange = 3
    Mango = 4

Fruits = []

@staticmethod
def add_fruits_to_list(fruits):
    TestClass.Fruits.extend(fruits)
    return "{0} fruits on the list".format(len(TestClass.Fruits))

Javonet SDK contains various methods to interact with enums and consume the results in Perl:

use strict;
use warnings;
use Nice::Try;
use aliased 'Javonet::Javonet' => 'Javonet';

my $resources_directory = ".";

# use activate only once in your app
Javonet->activate("your-license-key");

# create Jvm runtime context
my $called_runtime = Javonet->in_memory()->python();

# set up variables
my $library_path = "$resources_directory";
my $class_name = "TestClass.TestClass";

# load jvm custom library
$called_runtime->load_library($library_path);

# get type from the runtime
my $called_runtime_type = $called_runtime->get_type($class_name)->execute();

# get enum's items
my $fruit_1 = $called_runtime->get_enum_item($called_runtime_type, "Fruit", "Mango");
my $fruit_2 = $called_runtime->get_enum_item($called_runtime_type, "Fruit", "Orange");

# get items' names and values
my $fruit_1_name = $fruit_1->get_enum_name()->execute()->get_value();
my $fruit_1_value = $fruit_1->get_enum_value()->execute()->get_value();
my $fruit_2_name = $fruit_2->get_enum_name()->execute()->get_value();
my $fruit_2_value = $fruit_2->get_enum_value()->execute()->get_value();

# write result to console
my $result = "$fruit_1_name: $fruit_1_value, $fruit_2_name: $fruit_2_value";
print("$result\n");
import threading
import time

class TestClass:
    def __init__(self, public_value, private_value):
        self.public_value = public_value
        self.private_value = private_value
        

    from enum import Enum
    class Fruit(Enum):
        Apple = 1
        Banana = 2
        Orange = 3
        Mango = 4
    
    Fruits = []
    
    @staticmethod
    def add_fruits_to_list(fruits):
        TestClass.Fruits.extend(fruits)
        return "{0} fruits on the list".format(len(TestClass.Fruits))
# use activate only once in your app
Javonet->activate("your-license-key");

# create Jvm runtime context
my $called_runtime = Javonet->in_memory()->python();

# set up variables
my $library_path = "$resources_directory";
my $class_name = "TestClass.TestClass";

# load jvm custom library
$called_runtime->load_library($library_path);

# get type from the runtime
my $called_runtime_type = $called_runtime->get_type($class_name)->execute();

# get enum's items
my $fruit_1 = $called_runtime->get_enum_item($called_runtime_type, "Fruit", "Mango");
my $fruit_2 = $called_runtime->get_enum_item($called_runtime_type, "Fruit", "Orange");

# get items' names and values
my $fruit_1_name = $fruit_1->get_enum_name()->execute()->get_value();
my $fruit_1_value = $fruit_1->get_enum_value()->execute()->get_value();
my $fruit_2_name = $fruit_2->get_enum_name()->execute()->get_value();
my $fruit_2_value = $fruit_2->get_enum_value()->execute()->get_value();

# write result to console
my $result = "$fruit_1_name: $fruit_1_value, $fruit_2_name: $fruit_2_value";
print("$result\n");

This snippet uses in memory runtime bridging to load the Python package and next retrieves reference to specific enum type. Then two enum items are created. Their values and names are checked.

Enum items can be passed to Python package method:

This snippet doesn't support selected combination of technologies.

In this example, two enum items are created, too. Then array of enums is created and passed to method which adds enum items to list.

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.