make qcodes version lazy

Author: jenshnielsen

src/qcodes/__init__.py

@@ -12,15 +12,11 @@
 
 from typing_extensions import deprecated
 
-import qcodes._version
 import qcodes.configuration as qcconfig
 from qcodes.logger.logger import conditionally_start_all_logging
 from qcodes.utils import QCoDeSDeprecationWarning
 from qcodes.utils.spyder_utils import add_to_spyder_UMR_excludelist
 
-__version__ = qcodes._version.__version__
-
-
 config: qcconfig.Config = qcconfig.Config()
 
 conditionally_start_all_logging()
@@ -107,3 +103,23 @@ def test(**kwargs: Any) -> int:
 del deprecated
 
 test.__test__ = False  # type: ignore[attr-defined] # Don't try to run this method as a test
+
+
+def __getattr__(name: str) -> Any:
+    """
+    Getting __version__ is slow in an editable install since we have shell out to run git describe.
+    Here we only do it lazily if required.
+
+    TODO this means that the type of __version__ is Any, which is not ideal.
+    __version__ is also not listed by dir(qcodes) that could be fixed by overwrting __dir__.
+    see https://peps.python.org/pep-0562/
+    """
+    if name == "__version__":
+        import qcodes._version
+
+        __version__ = qcodes._version.__version__
+        return __version__
+    raise AttributeError(f"module {__name__!r} has no attribute {name!r}")
+
+
+__all__ = ["__version___", "config"]