Fix Python lib issue with sympy solver (#1165)

* Fix for Python sympy solver

* Add corresponding test

* Update requirements

---------

Co-authored-by: Luc Grosheintz <luc.grosheintz@gmail.com>

nmodl/__init__.py

@@ -1,7 +1,41 @@
+import os
+import sys
+
+if sys.version_info >= (3, 9):
+    from importlib.resources import files
+else:
+    from importlib_resources import files
+
+from find_libpython import find_libpython
+
+# try to add libpython*.so path to environment if not already set
+try:
+    os.environ["NMODL_PYLIB"] = os.environ.get(
+        "NMODL_PYLIB",
+        find_libpython(),
+    )
+except TypeError as exc:
+    raise RuntimeError(
+        "find_libpython was unable to find the Python library on this platform; "
+        "please make sure that the Python library is installed correctly\n"
+        "You can also try to manually set the NMODL_PYLIB environmental variable "
+        "to the Python library"
+    ) from exc
+
+# add nmodl home to environment (i.e. necessary for nrnunits.lib) if not
+# already set
+# `files` will automatically raise a `ModuleNotFoundError`
+os.environ["NMODLHOME"] = os.environ.get(
+    "NMODLHOME",
+    str(files("nmodl") / ".data"),
+)
+
+
 try:
     # Try importing but catch exception in case bindings are not available
     from ._nmodl import NmodlDriver, to_json, to_nmodl  # noqa
     from ._nmodl import __version__
+
     __all__ = ["NmodlDriver", "to_json", "to_nmodl"]
 except ImportError:
     print("[NMODL] [warning] :: Python bindings are not available")

requirements.txt

@@ -6,3 +6,4 @@ sympy
 numpy
 find_libpython
 scikit-build
+importlib_resources;python_version<"3.9"

setup.py

@@ -76,7 +76,8 @@ def run(self, *args, **kwargs):
 install_requirements = [
     "PyYAML>=3.13",
     "sympy>=1.3",
-    "find_libpython"
+    "find_libpython",
+    "importlib_resources;python_version<'3.9'",
 ]
 
 

test/unit/pybind/test_visitor.py

@@ -109,3 +109,18 @@ def visit_range_var(self, node):
 }
 """
     assert str(modast) == one_var_after
+
+
+def test_sympy_conductance_visitor():
+    """
+    Make sure NMODL sets the correct env variables to be able to run the sympy visitor
+    """
+    program = """NEURON {
+        USEION na READ ena WRITE ina
+        RANGE gna
+    }
+    BREAKPOINT {
+        ina = gna*(v - ena)
+    }"""
+    driver = nmodl.NmodlDriver()
+    visitor.SympyConductanceVisitor().visit_program(driver.parse_string(program))