ENH: ensure yt.utils.funcs.ensure_numpy_array consistently returns a copy

Author: neutrinoceros

yt/funcs.py

@@ -85,16 +85,9 @@ def ensure_numpy_array(obj):
     """
     This function ensures that *obj* is a numpy array. Typically used to
     convert scalar, list or tuple argument passed to functions using Cython.
+    Always return a copy of the input data.
     """
-    if isinstance(obj, np.ndarray):
-        if obj.shape == ():
-            return np.array([obj])
-        # We cast to ndarray to catch ndarray subclasses
-        return np.array(obj)
-    elif isinstance(obj, (list, tuple)):
-        return np.asarray(obj)
-    else:
-        return np.asarray([obj])
+    return np.atleast_1d(np.array(obj))
 
 
 def read_struct(f, fmt):