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# encoding: utf-8
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"""
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IO related utilities.
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"""
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#-----------------------------------------------------------------------------
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# Copyright (C) 2008-2011 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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from __future__ import print_function
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#-----------------------------------------------------------------------------
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# Imports
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#-----------------------------------------------------------------------------
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import codecs
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import os
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import sys
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import tempfile
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from StringIO import StringIO
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from .py3compat import PY3
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#-----------------------------------------------------------------------------
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# Code
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#-----------------------------------------------------------------------------
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class IOStream:
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def __init__(self,stream, fallback=None):
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if not hasattr(stream,'write') or not hasattr(stream,'flush'):
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if fallback is not None:
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stream = fallback
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else:
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raise ValueError("fallback required, but not specified")
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self.stream = stream
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self._swrite = stream.write
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# clone all methods not overridden:
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def clone(meth):
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return not hasattr(self, meth) and not meth.startswith('_')
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for meth in filter(clone, dir(stream)):
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setattr(self, meth, getattr(stream, meth))
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def write(self,data):
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try:
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self._swrite(data)
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except:
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try:
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# print handles some unicode issues which may trip a plain
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# write() call. Emulate write() by using an empty end
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# argument.
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print(data, end='', file=self.stream)
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except:
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# if we get here, something is seriously broken.
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print('ERROR - failed to write data to stream:', self.stream,
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file=sys.stderr)
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def writelines(self, lines):
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if isinstance(lines, basestring):
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lines = [lines]
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for line in lines:
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self.write(line)
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# This class used to have a writeln method, but regular files and streams
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# in Python don't have this method. We need to keep this completely
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# compatible so we removed it.
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@property
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def closed(self):
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return self.stream.closed
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def close(self):
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pass
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# setup stdin/stdout/stderr to sys.stdin/sys.stdout/sys.stderr
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devnull = open(os.devnull, 'a')
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stdin = IOStream(sys.stdin, fallback=devnull)
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stdout = IOStream(sys.stdout, fallback=devnull)
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stderr = IOStream(sys.stderr, fallback=devnull)
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class IOTerm:
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""" Term holds the file or file-like objects for handling I/O operations.
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These are normally just sys.stdin, sys.stdout and sys.stderr but for
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Windows they can can replaced to allow editing the strings before they are
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displayed."""
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# In the future, having IPython channel all its I/O operations through
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# this class will make it easier to embed it into other environments which
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# are not a normal terminal (such as a GUI-based shell)
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def __init__(self, stdin=None, stdout=None, stderr=None):
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mymodule = sys.modules[__name__]
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self.stdin = IOStream(stdin, mymodule.stdin)
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self.stdout = IOStream(stdout, mymodule.stdout)
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self.stderr = IOStream(stderr, mymodule.stderr)
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class Tee(object):
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"""A class to duplicate an output stream to stdout/err.
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This works in a manner very similar to the Unix 'tee' command.
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When the object is closed or deleted, it closes the original file given to
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it for duplication.
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"""
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# Inspired by:
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# http://mail.python.org/pipermail/python-list/2007-May/442737.html
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def __init__(self, file_or_name, mode="w", channel='stdout'):
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"""Construct a new Tee object.
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Parameters
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----------
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file_or_name : filename or open filehandle (writable)
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File that will be duplicated
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mode : optional, valid mode for open().
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If a filename was give, open with this mode.
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channel : str, one of ['stdout', 'stderr']
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"""
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if channel not in ['stdout', 'stderr']:
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raise ValueError('Invalid channel spec %s' % channel)
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if hasattr(file_or_name, 'write') and hasattr(file_or_name, 'seek'):
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self.file = file_or_name
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else:
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self.file = open(file_or_name, mode)
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self.channel = channel
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self.ostream = getattr(sys, channel)
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setattr(sys, channel, self)
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self._closed = False
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def close(self):
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"""Close the file and restore the channel."""
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self.flush()
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setattr(sys, self.channel, self.ostream)
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self.file.close()
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self._closed = True
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def write(self, data):
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"""Write data to both channels."""
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self.file.write(data)
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self.ostream.write(data)
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self.ostream.flush()
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def flush(self):
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"""Flush both channels."""
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self.file.flush()
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self.ostream.flush()
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def __del__(self):
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if not self._closed:
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self.close()
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def ask_yes_no(prompt,default=None):
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"""Asks a question and returns a boolean (y/n) answer.
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If default is given (one of 'y','n'), it is used if the user input is
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empty. Otherwise the question is repeated until an answer is given.
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An EOF is treated as the default answer. If there is no default, an
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exception is raised to prevent infinite loops.
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Valid answers are: y/yes/n/no (match is not case sensitive)."""
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answers = {'y':True,'n':False,'yes':True,'no':False}
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ans = None
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while ans not in answers.keys():
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try:
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ans = raw_input(prompt+' ').lower()
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if not ans: # response was an empty string
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ans = default
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except KeyboardInterrupt:
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pass
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except EOFError:
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if default in answers.keys():
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ans = default
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print()
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else:
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raise
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return answers[ans]
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def temp_pyfile(src, ext='.py'):
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"""Make a temporary python file, return filename and filehandle.
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Parameters
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----------
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src : string or list of strings (no need for ending newlines if list)
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Source code to be written to the file.
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ext : optional, string
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Extension for the generated file.
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Returns
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-------
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(filename, open filehandle)
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It is the caller's responsibility to close the open file and unlink it.
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"""
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fname = tempfile.mkstemp(ext)[1]
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f = open(fname,'w')
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f.write(src)
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f.flush()
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return fname, f
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def raw_print(*args, **kw):
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"""Raw print to sys.__stdout__, otherwise identical interface to print()."""
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print(*args, sep=kw.get('sep', ' '), end=kw.get('end', '\n'),
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file=sys.__stdout__)
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sys.__stdout__.flush()
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def raw_print_err(*args, **kw):
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"""Raw print to sys.__stderr__, otherwise identical interface to print()."""
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print(*args, sep=kw.get('sep', ' '), end=kw.get('end', '\n'),
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file=sys.__stderr__)
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sys.__stderr__.flush()
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# Short aliases for quick debugging, do NOT use these in production code.
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rprint = raw_print
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rprinte = raw_print_err
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class CapturedIO(object):
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"""Simple object for containing captured stdout/err StringIO objects"""
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def __init__(self, stdout, stderr):
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self._stdout = stdout
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self._stderr = stderr
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def __str__(self):
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return self.stdout
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@property
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def stdout(self):
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if not self._stdout:
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return ''
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return self._stdout.getvalue()
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@property
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def stderr(self):
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if not self._stderr:
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return ''
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return self._stderr.getvalue()
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def show(self):
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"""write my output to sys.stdout/err as appropriate"""
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sys.stdout.write(self.stdout)
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sys.stderr.write(self.stderr)
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sys.stdout.flush()
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sys.stderr.flush()
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__call__ = show
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class capture_output(object):
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"""context manager for capturing stdout/err"""
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stdout = True
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stderr = True
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def __init__(self, stdout=True, stderr=True):
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self.stdout = stdout
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self.stderr = stderr
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def __enter__(self):
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self.sys_stdout = sys.stdout
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self.sys_stderr = sys.stderr
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stdout = stderr = False
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if self.stdout:
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stdout = sys.stdout = StringIO()
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if self.stderr:
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stderr = sys.stderr = StringIO()
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return CapturedIO(stdout, stderr)
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def __exit__(self, exc_type, exc_value, traceback):
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sys.stdout = self.sys_stdout
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sys.stderr = self.sys_stderr
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def unicode_std_stream(stream='stdout'):
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u"""Get a wrapper to write unicode to stdout/stderr as UTF-8.
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This ignores environment variables and default encodings, to reliably write
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unicode to stdout or stderr.
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::
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unicode_std_stream().write(u'ł@e¶ŧ←')
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"""
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assert stream in ('stdout', 'stderr')
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stream = getattr(sys, stream)
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if PY3:
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try:
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stream_b = stream.buffer
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except AttributeError:
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# sys.stdout has been replaced - use it directly
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return stream
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else:
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stream_b = stream
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return codecs.getwriter('utf-8')(stream_b)
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