new clawutil.util module containing fullpath_import

src/python/clawutil/util.py

@@ -0,0 +1,66 @@
+r"""
+clawutil.util Module  `$CLAW/clawutil/src/python/clawutil/util.py`
+
+Provides general utility functions.
+
+:Functions:
+
+ - fullpath_import: import a module using its full path
+
+"""
+
+import os, sys, importlib
+from pathlib import Path
+
+
+def fullpath_import(fullpath, verbose=False):
+    """
+    Return a module imported from a full path name, e.g. if you have
+    a personal enhanced version of the geoclaw topotools module at
+    /full/path/to/topotools.py then instead of:
+
+        from clawpack.geoclaw import topotools
+
+    use:
+
+        from clawpack.clawutil.util import fullpath_import
+        topotools = fullpath_import('/full/path/to/topotools.py')
+
+    Relative imports also work, e.g.
+
+        topotools = fullpath_import('../topotools.py')
+
+    To reload the module if you make changes to it, use this function again
+    (rather than using importlib.reload).
+
+    Input `fullpath` can also be a `pathlib.Path` object instead of a string.
+
+    If `fullpath` is a string that starts with `$`, then the path is assumed
+    to start with an environment variable and this is resolved, if possible,
+    from `os.environ`.  For example, this works:
+
+        setrun_file = '$CLAW/amrclaw/examples/advection_2d_swirl/setrun.py'
+        setrun = util.fullpath_import(setrun_file)
+
+    It also expands `~` and `~user` constructs and resolves symlinks.
+    """
+
+    # expand any environment variables:
+    fullpath = os.path.expandvars(fullpath)
+
+    # convert to a Path object if necessary, expand user prefix `~`,
+    # and convert to absolute path, resolving any symlinks:
+    fullPath = Path(fullpath).expanduser().resolve()
+
+    assert fullPath.suffix == '.py', '*** Expecting path to .py file'
+
+    fname = fullPath.name     # should be modname.py
+    modname = fullPath.stem   # without extension
+
+    spec = importlib.util.spec_from_file_location(modname, fullPath)
+    module = importlib.util.module_from_spec(spec)
+    spec.loader.exec_module(module)
+    sys.modules[modname] = module
+    if verbose:
+        print('loaded module from file: ',module.__file__)
+    return module