Fix handling of generate_plot() in pynml module

examples/LeakConductance.mod

@@ -3,9 +3,9 @@ TITLE Mod file for component: Component(id=LeakConductance type=ionChannelHH)
 COMMENT
 
     This NEURON file has been generated by org.neuroml.export (see https://github.com/NeuroML/org.neuroml.export)
-         org.neuroml.export  v1.9.1
-         org.neuroml.model   v1.9.1
-         jLEMS               v0.10.8
+         org.neuroml.export  v1.10.0
+         org.neuroml.model   v1.10.0
+         jLEMS               v0.11.0
 
 ENDCOMMENT
 

pyneuroml/pynml.py

@@ -53,23 +53,54 @@
     if "matplotlib" in k:
         matplotlib_imported = True
         break
+
 if matplotlib_imported is True:
     # to maintain API compatibility:
     # so that existing scripts that use: from pynml import generate_plot
     # continue to work
     from pyneuroml.plot import generate_plot, generate_interactive_plot  # noqa
 else:
-    logger.warning("Matplotlib has not been imported, not importing plotting functions")
-    logger.warning("Please import these explicitly from pyneuroml.plot")
-    warnings.warn(
-        """
-        Please note that these plotting methods will be removed from the pynml
-        module in the future. Please import plotting methods expliclitly from
-        the pyneuroml.plot sub module.
-        """,
-        FutureWarning,
-        stacklevel=2,
-    )
+    # Define a new method, which only gets called if a user explicitly tries to 
+    # run generate_plot (and so requires matplotlib). If it's never called, matplotlib
+    # doesn't get imported
+
+    def generate_plot(*args, **kwargs):
+        try:
+            import matplotlib
+            from pyneuroml.plot import generate_plot as gp
+            return gp(*args, **kwargs)
+
+        except Exception as e:
+
+            logger.error("Matplotlib not found!")
+            warnings.warn(
+                """
+                Please note that these plotting methods will be removed from the pynml
+                module in the future. Please import plotting methods explicitly from
+                the pyneuroml.plot sub module.
+                """,
+                FutureWarning,
+                stacklevel=2,
+            )
+
+    def generate_interactive_plot(*args, **kwargs):
+        try:
+            import matplotlib
+            from pyneuroml.plot import generate_interactive_plot as gp
+            return gp(*args, **kwargs)
+
+        except Exception as e:
+
+            logger.error("Matplotlib not found!")
+            warnings.warn(
+                """
+                Please note that these plotting methods will be removed from the pynml
+                module in the future. Please import plotting methods explicitly from
+                the pyneuroml.plot sub module.
+                """,
+                FutureWarning,
+                stacklevel=2,
+            )
 
 DEFAULTS = {
     "v": False,