Improve python API, use import edm4hep instead of `from edm4hep imp…

…ort edm4hep` (#207)

README.md

@@ -78,7 +78,7 @@ the clases individually (for working with collections podio has its own
 bindings). Make sure that `<CMAKE_INSTALL_PREFIX>/lib` is in `LD_LIBRARY_PATH`,
 `<CMAKE_PREFIX_PATH>/python` is in `PYTHONPATH` and `<CMAKE_INSTALL_PREFIX>/include` is in `ROOT_INCLUDE_PATH`:
 ```python
-from edm4hep import edm4hep
+import edm4hep
 particle = edm4hep.MCParticle() # default initialized particle
 particle.getCharge() # 0.0
 
@@ -92,6 +92,9 @@ mc.setPDG(2212)
 mc.getPDG() # 2212
 ```
 
+In an interactive session (with `python` or `ipython`, for example) it's
+possible to see all the classes by typing `edm4hep.` and then pressing TAB.
+
 ## Contributing
 
 Contributions and bug reports are welcome! See our [contributing

python/edm4hep/__init__.py

@@ -1,6 +1,27 @@
 """Python module for the EDM4HEP datamodel and utilities."""
+import sys
 
-from .datamodel import Datamodel, Utils
 from .__version__ import __version__
-edm4hep = Datamodel()
-utils = Utils()
+import ROOT
+res = ROOT.gSystem.Load('libedm4hepDict.so')
+if res < 0:
+    raise RuntimeError('Failed to load libedm4hepDict.so')
+
+res = ROOT.gSystem.Load('libedm4hepRDF.so')
+if res < 0:
+    raise RuntimeError('Failed to load libedm4hepRDF.so')
+
+res = ROOT.gInterpreter.LoadFile('edm4hep/utils/kinematics.h')
+if res != 0:
+    raise RuntimeError('Failed to load kinematics.h')
+
+res = ROOT.gInterpreter.LoadFile('edm4hep/utils/dataframe.h')
+if res != 0:
+    raise RuntimeError('Failed to load dataframe.h')
+from ROOT import edm4hep
+
+# Make TAB completion work for utils
+setattr(edm4hep, 'utils', edm4hep.utils)
+
+# Make `import edm4hep` work
+sys.modules['edm4hep'] = edm4hep

test/test_rdf.py

@@ -1,7 +1,7 @@
 #!/usr/bin/env python3
 
 import ROOT
-from edm4hep import edm4hep
+import edm4hep
 
 ROOT.EnableImplicitMT()
 

test/utils/test_kinematics.py

@@ -3,7 +3,7 @@
 import unittest
 import cppyy
 
-from edm4hep import edm4hep
+import edm4hep
 
 # A few shorthands for slightly easier to read tests below
 p4 = edm4hep.utils.p4