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# encoding: utf-8
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"""
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Trap stdout/stderr, including at the OS level. Calls a callback with
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the output each time Python tries to write to the stdout or stderr.
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"""
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__docformat__ = "restructuredtext en"
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#-------------------------------------------------------------------------------
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# Copyright (C) 2008 The IPython Development Team
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#
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# Distributed under the terms of the BSD License. The full license is in
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# the file COPYING, distributed as part of this software.
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#-------------------------------------------------------------------------------
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#-------------------------------------------------------------------------------
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# Imports
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#-------------------------------------------------------------------------------
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from fd_redirector import FDRedirector, STDOUT, STDERR
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from IPython.kernel.core.file_like import FileLike
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from IPython.kernel.core.output_trap import OutputTrap
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class RedirectorOutputTrap(OutputTrap):
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""" Object which can trap text sent to stdout and stderr.
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"""
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#------------------------------------------------------------------------
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# OutputTrap interface.
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#------------------------------------------------------------------------
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def __init__(self, out_callback, err_callback):
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"""
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out_callback : callable called when there is output in the stdout
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err_callback : callable called when there is output in the stderr
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"""
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# Callback invoked on write to stdout and stderr
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self.out_callback = out_callback
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self.err_callback = err_callback
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# File descriptor redirectors, to capture non-Python
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# output.
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self.out_redirector = FDRedirector(STDOUT)
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self.err_redirector = FDRedirector(STDERR)
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# Call the base class with file like objects that will trigger
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# our callbacks
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OutputTrap.__init__(self, out=FileLike(self.on_out_write),
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err=FileLike(self.on_err_write), )
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def set(self):
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""" Set the hooks: set the redirectors and call the base class.
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"""
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self.out_redirector.start()
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self.err_redirector.start()
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OutputTrap.set(self)
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def unset(self):
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""" Remove the hooks: call the base class and stop the
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redirectors.
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"""
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OutputTrap.unset(self)
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# Flush the redirectors before stopping them
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self.on_err_write('')
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self.err_redirector.stop()
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self.on_out_write('')
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self.out_redirector.stop()
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#------------------------------------------------------------------------
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# Callbacks for synchronous output
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#------------------------------------------------------------------------
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def on_out_write(self, string):
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""" Callback called when there is some Python output on stdout.
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"""
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try:
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self.out_callback(self.out_redirector.getvalue() + string)
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except:
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# If tracebacks are happening and we can't see them, it is
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# quasy impossible to debug
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self.unset()
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raise
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def on_err_write(self, string):
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""" Callback called when there is some Python output on stderr.
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"""
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try:
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self.err_callback(self.err_redirector.getvalue() + string)
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except:
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# If tracebacks are happening and we can't see them, it is
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# quasy impossible to debug
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self.unset()
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raise
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