[Python] Use local imports to delay pythonization library loading

This should fix errors on Windows where the `libROOTPythonizations` is
attempted to be loaded before the DLL directory is set correctly in
`ROOT/__init__.py`.

Author: guitargeek

bindings/pyroot/pythonizations/python/ROOT/_facade.py

@@ -7,10 +7,6 @@
 import cppyy
 import cppyy.ll
 
-from ._application import PyROOTApplication
-from ._numbadeclare import _NumbaDeclareDecorator
-from ._pythonization import pythonization
-
 
 class PyROOTConfiguration(object):
     """Class for configuring PyROOT"""
@@ -57,6 +53,8 @@ class ROOTFacade(types.ModuleType):
     """Facade class for ROOT module"""
 
     def __init__(self, module, is_ipython):
+        from ._pythonization import pythonization
+
         types.ModuleType.__init__(self, module.__name__)
 
         self.module = module
@@ -181,6 +179,8 @@ def _register_converters_and_executors(self):
             CPyCppyyRegisterExecutorAlias(name, target)
 
     def _finalSetup(self):
+        from ._application import PyROOTApplication
+
         # Prevent this method from being re-entered through the gROOT wrapper
         self.__dict__["gROOT"] = cppyy.gbl.ROOT.GetROOT()
 
@@ -443,6 +443,8 @@ def TMVA(self):
     # Create and overload Numba namespace
     @property
     def Numba(self):
+        from ._numbadeclare import _NumbaDeclareDecorator
+
         cppyy.cppdef("namespace Numba {}")
         ns = self._fallback_getattr("Numba")
         ns.Declare = staticmethod(_NumbaDeclareDecorator)

bindings/pyroot/pythonizations/python/ROOT/_pythonization/__init__.py

@@ -14,8 +14,6 @@
 
 import cppyy
 
-from ._generic import pythonize_generic
-
 # \cond INTERNALS
 gbl_namespace = cppyy.gbl
 # \endcond
@@ -70,6 +68,7 @@ def pythonization(class_name, ns="::", is_prefix=False):
 
         def passes_filter(class_name):
             return any(class_name.startswith(prefix) for prefix in target)
+
     else:
 
         def passes_filter(class_name):
@@ -114,6 +113,7 @@ def cppyy_pythonizor(klass, name):
                 name (string): name of the class that is the current candidate
                     to be pythonized.
             """
+            from ._generic import pythonize_generic
 
             fqn = klass.__cpp_name__
 

bindings/pyroot/pythonizations/python/ROOT/_pythonization/_generic.py

@@ -8,7 +8,6 @@
 # For the list of contributors see $ROOTSYS/README/CREDITS.                    #
 ################################################################################
 
-from ROOT.libROOTPythonizations import AddPrettyPrintingPyz
 
 def _add_getitem_checked(klass):
     # Parameters:
@@ -27,25 +26,28 @@ def getitem_checked(o, i):
         if i >= 0 and i < len(o):
             return o._getitem__unchecked(i)
         else:
-            raise IndexError('index out of range')
+            raise IndexError("index out of range")
 
     klass._getitem__unchecked = klass.__getitem__
     klass.__getitem__ = getitem_checked
 
+
 # Generic pythonizor for pretty printing that is applied to (almost) all classes
 def pythonize_generic(klass, name):
+    from ROOT.libROOTPythonizations import AddPrettyPrintingPyz
+
     # Parameters:
     # klass: class to be pythonized
     # name: string containing the name of the class
 
     # Add pretty printing via setting the __str__ special function
 
     # Exclude classes which have the method __str__ already defined in C++
-    m = getattr(klass, '__str__', None)
-    has_cpp_str = True if m is not None and type(m).__name__ == 'CPPOverload' else False
+    m = getattr(klass, "__str__", None)
+    has_cpp_str = True if m is not None and type(m).__name__ == "CPPOverload" else False
 
     # Exclude std::string with its own pythonization from cppyy
-    exclude = [ 'std::string' ]
+    exclude = ["std::string"]
 
     if name not in exclude and not has_cpp_str:
         AddPrettyPrintingPyz(klass)