Python 3允许从其他异常中引发异常，例如：
try:
raise CustomException()
except CustomException as e:
try:
raise TypeError() from e
except TypeError as e:
print(type(e.__cause__))
CustomException实例存储在异常对象的__cause__属性中。
上面的代码应显示CustomException。
是否有办法捕获原始异常，而不是新引发的异常？
try:
raise CustomException()
except CustomException as e:
try:
raise TypeError() from e
except CustomException as e:
print(type(e)) # should reach here
覆盖__subclasscheck__无效，因为我无权访问该实例，并且无法指定CustomException is a subclass of all classes or of the cause class。
是否有一种方法可以诱使Python认为我们正在捕获的异常属于__cause__类型？
答案 0 :(得分：1)
简单的解决方案：捕获所有异常并需要过滤器：
!SESSION 2019-04-01 11:11:38.525 -----------------------------------------------
eclipse.buildId=M20130204-1200
java.version=1.8.0_144
java.vendor=Oracle Corporation
BootLoader constants: OS=win32, ARCH=x86, WS=win32, NL=en_US
Framework arguments: -product org.eclipse.sdk.ide
Command-line arguments: -product org.eclipse.sdk.ide -data D:\Projects\TestSpec\workspaceMC/../runtime-EclipseApplication -dev file:D:/Projects/TestSpec/workspaceMC/.metadata/.plugins/org.eclipse.pde.core/Eclipse Application/dev.properties -os win32 -ws win32 -arch x86 -consoleLog
!ENTRY org.eclipse.e4.ui.workbench 4 0 2019-04-01 11:11:43.317
!MESSAGE Unable to create class 'org.eclipse.ui.internal.e4.compatibility.CompatibilityView' from bundle '409'
!STACK 0
org.eclipse.e4.core.di.InjectionException: java.lang.NoClassDefFoundError: com/sun/jna/Library
at org.eclipse.e4.core.internal.di.MethodRequestor.execute(MethodRequestor.java:63)
at org.eclipse.e4.core.internal.di.InjectorImpl.processAnnotated(InjectorImpl.java:861)
at org.eclipse.e4.core.internal.di.InjectorImpl.processAnnotated(InjectorImpl.java:841)
at org.eclipse.e4.core.internal.di.InjectorImpl.inject(InjectorImpl.java:113)
at org.eclipse.e4.core.internal.di.InjectorImpl.internalMake(InjectorImpl.java:321)
at org.eclipse.e4.core.internal.di.InjectorImpl.make(InjectorImpl.java:242)
at org.eclipse.e4.core.contexts.ContextInjectionFactory.make(ContextInjectionFactory.java:161)
at org.eclipse.e4.ui.internal.workbench.ReflectionContributionFactory.createFromBundle(ReflectionContributionFactory.java:102)
at org.eclipse.e4.ui.internal.workbench.ReflectionContributionFactory.doCreate(ReflectionContributionFactory.java:71)
at org.eclipse.e4.ui.internal.workbench.ReflectionContributionFactory.create(ReflectionContributionFactory.java:53)
at org.eclipse.e4.ui.workbench.renderers.swt.ContributedPartRenderer.createWidget(ContributedPartRenderer.java:141)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.createWidget(PartRenderingEngine.java:894)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:629)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$6.run(PartRenderingEngine.java:520)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.createGui(PartRenderingEngine.java:505)
at org.eclipse.e4.ui.workbench.renderers.swt.ElementReferenceRenderer.createWidget(ElementReferenceRenderer.java:74)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.createWidget(PartRenderingEngine.java:894)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:629)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:731)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.access$2(PartRenderingEngine.java:702)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$7.run(PartRenderingEngine.java:696)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.createGui(PartRenderingEngine.java:681)
at org.eclipse.e4.ui.workbench.renderers.swt.StackRenderer.showTab(StackRenderer.java:1115)
at org.eclipse.e4.ui.workbench.renderers.swt.LazyStackRenderer.postProcess(LazyStackRenderer.java:98)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:645)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:731)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.access$2(PartRenderingEngine.java:702)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$7.run(PartRenderingEngine.java:696)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.createGui(PartRenderingEngine.java:681)
at org.eclipse.e4.ui.workbench.renderers.swt.SWTPartRenderer.processContents(SWTPartRenderer.java:59)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:641)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:731)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.access$2(PartRenderingEngine.java:702)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$7.run(PartRenderingEngine.java:696)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.createGui(PartRenderingEngine.java:681)
at org.eclipse.e4.ui.workbench.renderers.swt.SWTPartRenderer.processContents(SWTPartRenderer.java:59)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:641)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:731)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.access$2(PartRenderingEngine.java:702)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$7.run(PartRenderingEngine.java:696)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.createGui(PartRenderingEngine.java:681)
at org.eclipse.e4.ui.workbench.renderers.swt.SWTPartRenderer.processContents(SWTPartRenderer.java:59)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:641)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:731)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.access$2(PartRenderingEngine.java:702)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$7.run(PartRenderingEngine.java:696)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.createGui(PartRenderingEngine.java:681)
at org.eclipse.e4.ui.workbench.renderers.swt.SWTPartRenderer.processContents(SWTPartRenderer.java:59)
at org.eclipse.e4.ui.workbench.renderers.swt.PerspectiveRenderer.processContents(PerspectiveRenderer.java:59)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:641)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:731)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.access$2(PartRenderingEngine.java:702)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$7.run(PartRenderingEngine.java:696)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.createGui(PartRenderingEngine.java:681)
at org.eclipse.e4.ui.workbench.renderers.swt.PerspectiveStackRenderer.showTab(PerspectiveStackRenderer.java:103)
at org.eclipse.e4.ui.workbench.renderers.swt.LazyStackRenderer.postProcess(LazyStackRenderer.java:98)
at org.eclipse.e4.ui.workbench.renderers.swt.PerspectiveStackRenderer.postProcess(PerspectiveStackRenderer.java:77)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:645)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:731)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.access$2(PartRenderingEngine.java:702)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$7.run(PartRenderingEngine.java:696)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.createGui(PartRenderingEngine.java:681)
at org.eclipse.e4.ui.workbench.renderers.swt.SWTPartRenderer.processContents(SWTPartRenderer.java:59)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:641)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:731)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.access$2(PartRenderingEngine.java:702)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$7.run(PartRenderingEngine.java:696)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.createGui(PartRenderingEngine.java:681)
at org.eclipse.e4.ui.workbench.renderers.swt.SWTPartRenderer.processContents(SWTPartRenderer.java:59)
at org.eclipse.e4.ui.workbench.renderers.swt.WBWRenderer.processContents(WBWRenderer.java:644)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:641)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.safeCreateGui(PartRenderingEngine.java:731)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.access$2(PartRenderingEngine.java:702)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$7.run(PartRenderingEngine.java:696)
at org.eclipse.core.runtime.SafeRunner.run(SafeRunner.java:42)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.createGui(PartRenderingEngine.java:681)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine$9.run(PartRenderingEngine.java:987)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
at org.eclipse.e4.ui.internal.workbench.swt.PartRenderingEngine.run(PartRenderingEngine.java:942)
at org.eclipse.e4.ui.internal.workbench.E4Workbench.createAndRunUI(E4Workbench.java:86)
at org.eclipse.ui.internal.Workbench$5.run(Workbench.java:588)
at org.eclipse.core.databinding.observable.Realm.runWithDefault(Realm.java:332)
at org.eclipse.ui.internal.Workbench.createAndRunWorkbench(Workbench.java:543)
at org.eclipse.ui.PlatformUI.createAndRunWorkbench(PlatformUI.java:149)
at org.eclipse.ui.internal.ide.application.IDEApplication.start(IDEApplication.java:124)
at org.eclipse.equinox.internal.app.EclipseAppHandle.run(EclipseAppHandle.java:196)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.runApplication(EclipseAppLauncher.java:110)
at org.eclipse.core.runtime.internal.adaptor.EclipseAppLauncher.start(EclipseAppLauncher.java:79)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:353)
at org.eclipse.core.runtime.adaptor.EclipseStarter.run(EclipseStarter.java:180)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.eclipse.equinox.launcher.Main.invokeFramework(Main.java:629)
at org.eclipse.equinox.launcher.Main.basicRun(Main.java:584)
at org.eclipse.equinox.launcher.Main.run(Main.java:1438)
at org.eclipse.equinox.launcher.Main.main(Main.java:1414)
Caused by: java.lang.NoClassDefFoundError: com/sun/jna/Library
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(Unknown Source)
at org.eclipse.osgi.internal.baseadaptor.DefaultClassLoader.defineClass(DefaultClassLoader.java:188)
at org.eclipse.osgi.baseadaptor.loader.ClasspathManager.defineClassHoldingLock(ClasspathManager.java:632)
at org.eclipse.osgi.baseadaptor.loader.ClasspathManager.defineClass(ClasspathManager.java:607)
at org.eclipse.osgi.baseadaptor.loader.ClasspathManager.findClassImpl(ClasspathManager.java:568)
at org.eclipse.osgi.baseadaptor.loader.ClasspathManager.findLocalClassImpl(ClasspathManager.java:492)
at org.eclipse.osgi.baseadaptor.loader.ClasspathManager.findLocalClass(ClasspathManager.java:465)
at org.eclipse.osgi.internal.baseadaptor.DefaultClassLoader.findLocalClass(DefaultClassLoader.java:216)
at org.eclipse.osgi.internal.loader.BundleLoader.findLocalClass(BundleLoader.java:395)
at org.eclipse.osgi.internal.loader.BundleLoader.findClassInternal(BundleLoader.java:464)
at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:421)
at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:412)
at org.eclipse.osgi.internal.baseadaptor.DefaultClassLoader.loadClass(DefaultClassLoader.java:107)
at java.lang.ClassLoader.loadClass(Unknown Source)
at DLLs.Release.test.testParser(test.java:23)
at mc_view.views.SampleView$ViewContentProvider.initialize(SampleView.java:162)
at mc_view.views.SampleView$ViewContentProvider.getElements(SampleView.java:115)
at org.eclipse.jface.viewers.StructuredViewer.getRawChildren(StructuredViewer.java:1010)
at org.eclipse.jface.viewers.ColumnViewer.getRawChildren(ColumnViewer.java:703)
at org.eclipse.jface.viewers.AbstractTreeViewer.getRawChildren(AbstractTreeViewer.java:1351)
at org.eclipse.jface.viewers.TreeViewer.getRawChildren(TreeViewer.java:391)
at org.eclipse.jface.viewers.StructuredViewer.getFilteredChildren(StructuredViewer.java:917)
at org.eclipse.jface.viewers.AbstractTreeViewer.getSortedChildren(AbstractTreeViewer.java:620)
at org.eclipse.jface.viewers.AbstractTreeViewer$1.run(AbstractTreeViewer.java:820)
at org.eclipse.swt.custom.BusyIndicator.showWhile(BusyIndicator.java:70)
at org.eclipse.jface.viewers.AbstractTreeViewer.createChildren(AbstractTreeViewer.java:797)
at org.eclipse.jface.viewers.TreeViewer.createChildren(TreeViewer.java:644)
at org.eclipse.jface.viewers.AbstractTreeViewer.createChildren(AbstractTreeViewer.java:768)
at org.eclipse.jface.viewers.AbstractTreeViewer.internalInitializeTree(AbstractTreeViewer.java:1548)
at org.eclipse.jface.viewers.TreeViewer.internalInitializeTree(TreeViewer.java:833)
at org.eclipse.jface.viewers.AbstractTreeViewer$5.run(AbstractTreeViewer.java:1532)
at org.eclipse.jface.viewers.StructuredViewer.preservingSelection(StructuredViewer.java:1443)
at org.eclipse.jface.viewers.TreeViewer.preservingSelection(TreeViewer.java:403)
at org.eclipse.jface.viewers.StructuredViewer.preservingSelection(StructuredViewer.java:1404)
at org.eclipse.jface.viewers.AbstractTreeViewer.inputChanged(AbstractTreeViewer.java:1525)
at org.eclipse.jface.viewers.ContentViewer.setInput(ContentViewer.java:280)
at org.eclipse.jface.viewers.StructuredViewer.setInput(StructuredViewer.java:1690)
at mc_view.views.SampleView.createPartControl(SampleView.java:197)
at org.eclipse.ui.internal.e4.compatibility.CompatibilityPart.createPartControl(CompatibilityPart.java:138)
at org.eclipse.ui.internal.e4.compatibility.CompatibilityView.createPartControl(CompatibilityView.java:155)
at org.eclipse.ui.internal.e4.compatibility.CompatibilityPart.create(CompatibilityPart.java:313)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.eclipse.e4.core.internal.di.MethodRequestor.execute(MethodRequestor.java:56)
... 106 more
Caused by: java.lang.ClassNotFoundException: com.sun.jna.Library
at org.eclipse.osgi.internal.loader.BundleLoader.findClassInternal(BundleLoader.java:501)
at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:421)
at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:412)
at org.eclipse.osgi.internal.baseadaptor.DefaultClassLoader.loadClass(DefaultClassLoader.java:107)
at java.lang.ClassLoader.loadClass(Unknown Source)
... 153 more
答案 1 :(得分：1)
如果您可以控制引发的异常，则可以使其成为引发的异常的子类：
try:
raise TypeError()
except TypeError as e:
try:
class CustomException(TypeError.__class__):
pass
raise CustomException() from e
except TypeError as e:
print(type(e)) # Reaches here
这就是说，“捉迷藏”机制旨在隐藏原始异常，以便以后的代码不依赖于实现细节。