interp: print a more informative message on SO loading failureHEADmaster

1 files changed, 13 insertions, 2 deletions

diff --git a/interp.py b/interp.py
index 6ba20bc..c7c6f64 100644
--- a/interp.py
+++ b/interp.py
@@ -1,4 +1,5 @@
 import ctypes
+from errno import ENOENT
 
 import numpy as np
 
@@ -75,6 +76,14 @@ def interp2d(src_start, src_step, src_val, dst_coords, stencil):
 
 _doubleptr = ctypes.POINTER(ctypes.c_double)
 
+class LibError(Exception):
+    _errmsg = """
+    Cannot load the interpolation library. Make sure you've built it (run 'make')
+    and the dynamic loader can locate it (e.g. add the directory to LD_LIBRARY_PATH).
+    """
+    def __init__(self):
+        super().__init__(self._errmsg)
+
 class Interp2D_C:
     _lib    = None
     _interp_func = None
@@ -93,8 +102,10 @@ class Interp2D_C:
     _ret_c = None
 
     def __init__(self, src_start, src_step, src_val, stencil):
-        self._lib = ctypes.CDLL('lib_interp_c.so')
-
+        try:
+            self._lib = ctypes.CDLL('lib_interp_c.so')
+        except OSError as e:
+            raise LibError
 
         func = getattr(self._lib, 'interp2d_%d' % stencil)
         func.argtypes = [_doubleptr, _doubleptr, _doubleptr,