Merge pull request numpy#16064 from keremh/fix-exception-raise

ENH: Fix exception causes in four .py files

Author: charris

numpy/lib/histograms.py

@@ -417,9 +417,9 @@ def _get_bin_edges(a, bins, range, weights):
     elif np.ndim(bins) == 0:
         try:
             n_equal_bins = operator.index(bins)
-        except TypeError:
+        except TypeError as e:
             raise TypeError(
-                '`bins` must be an integer, a string, or an array')
+                '`bins` must be an integer, a string, or an array') from e
         if n_equal_bins < 1:
             raise ValueError('`bins` must be positive, when an integer')
 

numpy/lib/index_tricks.py

@@ -368,8 +368,10 @@ def __getitem__(self, key):
                         if len(vec) == 3:
                             trans1d = int(vec[2])
                         continue
-                    except Exception:
-                        raise ValueError("unknown special directive")
+                    except Exception as e:
+                        raise ValueError(
+                            "unknown special directive {!r}".format(item)
+                        ) from e
                 try:
                     axis = int(item)
                     continue

numpy/lib/shape_base.py

@@ -372,8 +372,10 @@ def apply_along_axis(func1d, axis, arr, *args, **kwargs):
     # invoke the function on the first item
     try:
         ind0 = next(inds)
-    except StopIteration:
-        raise ValueError('Cannot apply_along_axis when any iteration dimensions are 0')
+    except StopIteration as e:
+        raise ValueError(
+            'Cannot apply_along_axis when any iteration dimensions are 0'
+        ) from None
     res = asanyarray(func1d(inarr_view[ind0], *args, **kwargs))
 
     # build a buffer for storing evaluations of func1d.

numpy/lib/ufunclike.py

@@ -188,9 +188,9 @@ def isposinf(x, out=None):
     is_inf = nx.isinf(x)
     try:
         signbit = ~nx.signbit(x)
-    except TypeError:
+    except TypeError as e:
         raise TypeError('This operation is not supported for complex values '
-                        'because it would be ambiguous.')
+                        'because it would be ambiguous.') from e
     else:
         return nx.logical_and(is_inf, signbit, out)
 
@@ -259,8 +259,8 @@ def isneginf(x, out=None):
     is_inf = nx.isinf(x)
     try:
         signbit = nx.signbit(x)
-    except TypeError:
+    except TypeError as e:
         raise TypeError('This operation is not supported for complex values '
-                        'because it would be ambiguous.')
+                        'because it would be ambiguous.') from e
     else:
         return nx.logical_and(is_inf, signbit, out)