import_all: skip single underscore

skip single underscore
minor restructure

Cython/Build/IpythonMagic.py

@@ -95,15 +95,16 @@ class CythonMagics(Magics):
     def _import_all(self, module):
         mdict = module.__dict__
         if '__all__' in mdict:
-            for k in mdict['__all__']:
-                if k in mdict:
-                    self.shell.push({k:mdict[k]})
+            keys = mdict['__all__']
         else:
-                    raise AttributeError("'module' object has no attribute '%s'" % k)
-        else:
-            for k, v in mdict.items():
-                if not k.startswith('__'):
-                    self.shell.push({k:v})
+            keys = [k for k in mdict if not k.startswith('_')]
+
+        for k in keys:
+            try:
+                self.shell.push({k: mdict[k]})
+            except KeyError:
+                msg = "'module' object has no attribute '%s'" % k
+                raise AttributeError(msg)
 
     @cell_magic
     def cython_inline(self, line, cell):