tst40.py

from __future__ import print_function

import ROOT

ROOT.gROOT.ProcessLine("""
#include <string>
class  A
{
  public:
  
   A ( int a )
   : m_a ( a ) 
   {} ;
   virtual ~A(){};
   virtual int num () const { return m_a   ; } 
   std::string line () const
   { return std::to_string ( this->num() ) ; }
  private:
  
    int m_a {0};
    
};
""")

class B (ROOT.A) :

    def __init__  ( self , b ) :
        ROOT.A.__init__ ( self , b ) 
    
    def a (self ) : return 10 



a = ROOT.A ( 5 )
print ('A-line', a.line() )

b = B  ( 6 )

print ('B-line', b.line() )  



"""
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
/afs/cern.ch/user/i/ibelyaev/cmtuser/RELEASE/ostap/build/tst40.py in <module>()
     35 print ('A-line', a.line() )
     36 
---> 37 b = B  ( 6 )
     38 
     39 print ('B-line', b.line() )

/afs/cern.ch/user/i/ibelyaev/cmtuser/RELEASE/ostap/build/tst40.py in __init__(self, b)
     26 
     27     def __init__  ( self , b ) :
---> 28         ROOT.A.__init__ ( self , b )
     29 
     30     def a (self ) : return 10

TypeError: none of the 2 overloaded methods succeeded. Full details:
  no constructor available for 'A'
  A::A(A&) =>
    TypeError: could not convert argument 1


"""