322 lines
11 KiB
Markdown
322 lines
11 KiB
Markdown
# wxPython:从任何地方捕捉异常
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> 原文：<https://www.blog.pythonlibrary.org/2014/03/14/wxpython-catching-exceptions-from-anywhere/>
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前几天，wxPython Google Group 正在讨论捕捉 wxPython 中异常的不同方法。如果您经常使用 wxPython，您将很快意识到有些异常很难捕捉。 [wxPython Wiki](http://wiki.wxpython.org/C%2B%2B%20%26%20Python%20Sandwich?action=show&redirect=CppAndPythonSandwich) 解释了原因。无论如何，名单上的人都推荐使用 **sys.excepthook** 。所以我采用了他们提到的一种方法，创建了一个小例子:
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```py
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import sys
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import traceback
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import wx
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########################################################################
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class Panel(wx.Panel):
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""""""
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#----------------------------------------------------------------------
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def __init__(self, parent):
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"""Constructor"""
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wx.Panel.__init__(self, parent)
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btn = wx.Button(self, label="Raise Exception")
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btn.Bind(wx.EVT_BUTTON, self.onExcept)
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#----------------------------------------------------------------------
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def onExcept(self, event):
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"""
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Raise an error
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"""
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1/0
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########################################################################
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class Frame(wx.Frame):
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""""""
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#----------------------------------------------------------------------
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def __init__(self):
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"""Constructor"""
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wx.Frame.__init__(self, None, title="Exceptions")
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sys.excepthook = MyExceptionHook
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panel = Panel(self)
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self.Show()
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########################################################################
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class ExceptionDialog(GMD.GenericMessageDialog):
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""""""
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#----------------------------------------------------------------------
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def __init__(self, msg):
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"""Constructor"""
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GMD.GenericMessageDialog.__init__(self, None, msg, "Exception!",
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wx.OK|wx.ICON_ERROR)
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#----------------------------------------------------------------------
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def MyExceptionHook(etype, value, trace):
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"""
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Handler for all unhandled exceptions.
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:param `etype`: the exception type (`SyntaxError`, `ZeroDivisionError`, etc...);
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:type `etype`: `Exception`
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:param string `value`: the exception error message;
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:param string `trace`: the traceback header, if any (otherwise, it prints the
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standard Python header: ``Traceback (most recent call last)``.
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"""
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frame = wx.GetApp().GetTopWindow()
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tmp = traceback.format_exception(etype, value, trace)
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exception = "".join(tmp)
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dlg = ExceptionDialog(exception)
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dlg.ShowModal()
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dlg.Destroy()
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#----------------------------------------------------------------------
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if __name__ == "__main__":
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app = wx.App(False)
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frame = Frame()
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app.MainLoop()
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```
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在这个例子中，我们创建了一个带有按钮的面板，这个按钮会故意引发一个异常。我们通过将 **sys.excepthook** 重定向到我们的 **MyExceptionHook** 函数来捕获异常。这个函数将格式化异常的回溯，格式化它使它可读，然后显示一个带有异常信息的对话框。wxPython 的创建者 Robin Dunn 认为，如果有人提出一个装饰器，我们可以用它来捕捉异常，然后作为一个例子添加到 [wiki 页面](http://wiki.wxpython.org/C%2B%2B%20%26%20Python%20Sandwich?action=show&redirect=CppAndPythonSandwich)，这将是一件好事。
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我对装潢师的第一个想法如下:
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```py
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import logging
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import wx
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########################################################################
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class ExceptionLogging(object):
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#----------------------------------------------------------------------
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def __init__(self, fn):
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self.fn = fn
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# create logging instance
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self.log = logging.getLogger("wxErrors")
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self.log.setLevel(logging.INFO)
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# create a logging file handler / formatter
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log_fh = logging.FileHandler("error.log")
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formatter = logging.Formatter("%(asctime)s - %(name)s - %(message)s")
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log_fh.setFormatter(formatter)
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self.log.addHandler(log_fh)
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#----------------------------------------------------------------------
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def __call__(self, evt):
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try:
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self.fn(self, evt)
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except Exception, e:
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self.log.exception("Exception")
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########################################################################
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class Panel(wx.Panel):
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""""""
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#----------------------------------------------------------------------
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def __init__(self, parent):
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"""Constructor"""
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wx.Panel.__init__(self, parent)
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btn = wx.Button(self, label="Raise Exception")
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btn.Bind(wx.EVT_BUTTON, self.onExcept)
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#----------------------------------------------------------------------
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@ExceptionLogging
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def onExcept(self, event):
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"""
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Raise an error
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"""
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1/0
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########################################################################
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class Frame(wx.Frame):
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""""""
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#----------------------------------------------------------------------
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def __init__(self):
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"""Constructor"""
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wx.Frame.__init__(self, None, title="Exceptions")
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panel = Panel(self)
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self.Show()
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#----------------------------------------------------------------------
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if __name__ == "__main__":
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app = wx.App(False)
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frame = Frame()
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app.MainLoop()
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```
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在这段代码中，我们创建了一个创建日志实例的类。然后我们覆盖 **__call__** 方法，将方法调用包装在异常处理程序中，这样我们就可以捕捉异常。基本上我们在这里做的是创建一个类装饰器。接下来，我们用异常日志记录类修饰一个事件处理程序。这并不完全是邓恩先生想要的，因为装饰者也需要能够包装其他功能。所以我编辑了一下，做了如下的小调整:
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```py
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import logging
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import wx
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class ExceptionLogging(object):
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def __init__(self, fn, *args, **kwargs):
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self.fn = fn
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# create logging instance
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self.log = logging.getLogger("wxErrors")
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self.log.setLevel(logging.INFO)
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# create a logging file handler / formatter
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log_fh = logging.FileHandler("error.log")
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formatter = logging.Formatter("%(asctime)s - %(name)s - %(message)s")
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log_fh.setFormatter(formatter)
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self.log.addHandler(log_fh)
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def __call__(self, *args, **kwargs):
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try:
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self.fn(self, *args, **kwargs)
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except Exception, e:
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self.log.exception("Exception")
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########################################################################
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class Panel(wx.Panel):
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""""""
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#----------------------------------------------------------------------
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def __init__(self, parent):
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"""Constructor"""
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wx.Panel.__init__(self, parent)
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btn = wx.Button(self, label="Raise Exception")
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btn.Bind(wx.EVT_BUTTON, self.onExcept)
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#----------------------------------------------------------------------
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@ExceptionLogging
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def onExcept(self, event):
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"""
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Raise an error
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"""
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1/0
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########################################################################
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class Frame(wx.Frame):
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""""""
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#----------------------------------------------------------------------
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def __init__(self):
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"""Constructor"""
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wx.Frame.__init__(self, None, title="Exceptions")
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panel = Panel(self)
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self.Show()
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#----------------------------------------------------------------------
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if __name__ == "__main__":
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app = wx.App(False)
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frame = Frame()
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app.MainLoop()
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```
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这一次， **__call__** 方法可以接受任意数量的参数或关键字参数，这给了它更多的灵活性。这仍然不是罗宾·邓恩想要的，所以他写了下面的例子:
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```py
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from __future__ import print_function
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import logging
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import wx
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print(wx.version())
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def exceptionLogger(func, loggerName=''):
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"""
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A simple decorator that will catch and log any exceptions that may occur
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to the root logger.
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"""
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assert callable(func)
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mylogger = logging.getLogger(loggerName)
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# wrap a new function around the callable
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def logger_func(*args, **kw):
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try:
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if not kw:
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return func(*args)
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return func(*args, **kw)
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except Exception:
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mylogger.exception('Exception in %s:', func.__name__)
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logger_func.__name__ = func.__name__
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logger_func.__doc__ = func.__doc__
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if hasattr(func, '__dict__'):
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logger_func.__dict__.update(func.__dict__)
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return logger_func
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def exceptionLog2Logger(loggerName):
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"""
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A decorator that will catch and log any exceptions that may occur
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to the named logger.
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"""
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import functools
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return functools.partial(exceptionLogger, loggerName=loggerName)
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########################################################################
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class Panel(wx.Panel):
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""""""
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#----------------------------------------------------------------------
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def __init__(self, parent):
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"""Constructor"""
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wx.Panel.__init__(self, parent)
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btn = wx.Button(self, label="Raise Exception")
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btn.Bind(wx.EVT_BUTTON, self.onExcept)
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#----------------------------------------------------------------------
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@exceptionLog2Logger('testLogger')
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def onExcept(self, event):
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"""
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Raise an error
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"""
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print(self, event)
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print(isinstance(self, wx.Panel))
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#trigger an exception
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1/0
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########################################################################
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class Frame(wx.Frame):
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""""""
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#----------------------------------------------------------------------
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def __init__(self):
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"""Constructor"""
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wx.Frame.__init__(self, None, title="Exceptions")
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panel = Panel(self)
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self.Show()
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#----------------------------------------------------------------------
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if __name__ == "__main__":
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# set up the default logger
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log = logging.getLogger('testLogger')
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log.setLevel(logging.INFO)
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# create a logging file handler / formatter
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log_fh = logging.FileHandler("error.log")
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formatter = logging.Formatter("%(asctime)s - %(name)s - %(message)s")
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log_fh.setFormatter(formatter)
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log.addHandler(log_fh)
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app = wx.App(False)
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frame = Frame()
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app.MainLoop()
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```
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这展示了几个不同的装饰器示例。这个例子展示了更传统的装饰器构造方法。虽然它有更多的元编程。第一个示例检查以确保传递给它的内容实际上是可调用的。然后，它创建一个记录器，并用一个异常处理程序包装可调用的。在它返回包装的函数之前，包装的函数被修改，以便它与传递给它的原始函数具有相同的名称和 docstring。我相信你可以放弃它，使用 [functools.wraps](http://docs.python.org/2/library/functools.html#functools.wraps) 来代替，但是在教程中明确一点可能更好。
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* * *
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### 包扎
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现在你知道如何用几种不同的方法捕捉异常了。希望这对您自己的应用程序设计有所帮助。玩得开心！ |