Defer external dependency check to DilcaDistance init

make function out of external depency checking code

cdcstream/__init__.py

@@ -21,31 +21,5 @@
 __version__ = '0.2.0'
 
 
-import sys
-import logging
-
 from .cdcstream import DriftDetector, CDCStream
 from .dilca_wrapper import DilcaDistance, dilca_workflow
-
-from . import tools
-
-
-logger = logging.getLogger(__name__)
-
-WEKA_DEPENDENCIES = [DilcaDistance]
-
-
-# Check if external dependencies fulfilled
-tools.manage_jvm_start()
-any_installations = False
-for dep in WEKA_DEPENDENCIES:
-    installed = tools.check_package_installed(
-        package_name=dep._weka_package_name, package_version=dep._weka_package_version_min,
-        raise_error=False)
-    if not installed:
-        any_installations = True
-        tools.attempt_install_package(package_name=dep._weka_package_name, defer_application_exit=True)
-if any_installations:
-    logger.warning('An application restart is necessary - exiting.')
-    tools.manage_jvm_stop()
-    sys.exit(0)

cdcstream/dilca_wrapper.py

@@ -82,7 +82,10 @@ def __init__(self, supervised=False, attribute_indices=None):
         tools.manage_jvm_start()
 
         _jobject = DistanceFunction.new_instance('weka.core.' + self._weka_package_name)
-        self.enforce_type(_jobject, 'weka.core.DistanceFunction')
+        try:
+            self.enforce_type(_jobject, 'weka.core.DistanceFunction')
+        except AssertionError:  # does not feel elegant...
+            tools.manage_external_dependencies(weka_depends=[self.__class__])
         super().__init__(jobject=_jobject, options=None)
         self.is_optionhandler = True  # forcefully...
 

cdcstream/tools.py

@@ -1,6 +1,7 @@
 
 import sys
 import logging
+from typing import List
 
 import weka.core.jvm as jvm
 from weka.core import packages
@@ -32,6 +33,26 @@ def manage_jvm_detach():
 def manage_jvm_stop():
     jvm.stop()
 
+def manage_external_dependencies(weka_depends: List[object]) -> None:
+    """Checks whether external WEKA packages associated to passed interfaces are installed.
+
+    Args:
+        weka_depends (List[object]): The interfaces/classes.
+    """
+    manage_jvm_start()
+    any_installations = False
+    for dep in weka_depends:
+        installed = check_package_installed(
+            package_name=dep._weka_package_name, package_version=dep._weka_package_version_min,
+            raise_error=False)
+        if not installed:
+            any_installations = True
+            attempt_install_package(package_name=dep._weka_package_name, defer_application_exit=True)
+    if any_installations:
+        logger.warning('An application restart is necessary - exiting.')
+        manage_jvm_stop()
+        sys.exit(0)
+
 def check_package_installed(package_name, package_version=None, raise_error=False):
     res = packages.is_installed(package_name, version=None)
     if res and package_version: