diff --git a/hydpy/__init__.py b/hydpy/__init__.py
index <HASH>..<HASH> 100644
--- a/hydpy/__init__.py
+++ b/hydpy/__init__.py
@@ -180,6 +180,8 @@ from hydpy.exe.servertools import (
 )
 
 
+__version__ = "4.0a18"
+
 pub.options = optiontools.Options()
 pub.indexer = indextools.Indexer()
 pub.config = configutils.Config()
Make HydPy's version number programmatically available via a __version__ attribute following PEP <I>.

First step to solve issue hydpy-dev/OpenDA#3.