This recipe discribes how to change the implementation of the _run_child method in Popen3 at runtime.
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# The purpose of this code is to replace the implementation of popen2.popen* such # that you can pass Unicode strings to those functions. The Unicode string will # be converted to a plain string using the UTF-8 encoding. # The more interesting point made here is that it is possible, and reasonably easy, # to change the implementation of a method at runtime import popen2 # This is the replacement routine. All it does in convert the cmd to UTF-8 and pass it # to the original method. The original method is saved as a default argument (this # takes advantage of the fact that default arguments are only evaluated once in # Python). def _run_child_withencoding(self, cmd, old_run_child = popen2.Popen3._run_child): return old_run_child(self, cmd.encode('utf-8')) # Replace the _run_child method in the Popen3 class with out new implementation popen2.Popen3._run_child = _run_child_withencoding # Note that the technique for changing a an method on an instance, instead of a # class, is somewhat different because Python differentiates between bound and # unbound instances. But that's for a different recipe :-)