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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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from __future__ import absolute_import
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#-----------------------------------------------------------------------------
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# Imports
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#-----------------------------------------------------------------------------
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import codecs
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from contextlib import contextmanager
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import io
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import os
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import shutil
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import stat
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import sys
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import tempfile
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from .capture import CapturedIO, capture_output
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from .py3compat import string_types, input, 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 __repr__(self):
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cls = self.__class__
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tpl = '{mod}.{cls}({args})'
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return tpl.format(mod=cls.__module__, cls=cls.__name__, args=self.stream)
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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, string_types):
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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, 'w')
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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, interrupt=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. If interrupt is given (one of 'y','n'), it is used if the user
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presses Ctrl-C. Otherwise the question is repeated until an answer is
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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 = 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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if interrupt:
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ans = interrupt
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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 _copy_metadata(src, dst):
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"""Copy the set of metadata we want for atomic_writing.
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Permission bits and flags. We'd like to copy file ownership as well, but we
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can't do that.
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"""
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shutil.copymode(src, dst)
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st = os.stat(src)
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if hasattr(os, 'chflags') and hasattr(st, 'st_flags'):
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os.chflags(dst, st.st_flags)
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@contextmanager
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def atomic_writing(path, text=True, encoding='utf-8', **kwargs):
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"""Context manager to write to a file only if the entire write is successful.
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This works by creating a temporary file in the same directory, and renaming
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it over the old file if the context is exited without an error. If other
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file names are hard linked to the target file, this relationship will not be
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preserved.
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On Windows, there is a small chink in the atomicity: the target file is
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deleted before renaming the temporary file over it. This appears to be
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unavoidable.
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Parameters
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----------
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path : str
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The target file to write to.
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text : bool, optional
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Whether to open the file in text mode (i.e. to write unicode). Default is
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True.
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encoding : str, optional
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The encoding to use for files opened in text mode. Default is UTF-8.
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**kwargs
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Passed to :func:`io.open`.
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"""
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# realpath doesn't work on Windows: http://bugs.python.org/issue9949
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# Luckily, we only need to resolve the file itself being a symlink, not
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# any of its directories, so this will suffice:
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if os.path.islink(path):
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path = os.path.join(os.path.dirname(path), os.readlink(path))
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dirname, basename = os.path.split(path)
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handle, tmp_path = tempfile.mkstemp(prefix=basename, dir=dirname)
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if text:
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fileobj = io.open(handle, 'w', encoding=encoding, **kwargs)
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else:
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fileobj = io.open(handle, 'wb', **kwargs)
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try:
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yield fileobj
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except:
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fileobj.close()
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os.remove(tmp_path)
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raise
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# Flush to disk
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fileobj.flush()
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os.fsync(fileobj.fileno())
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# Written successfully, now rename it
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fileobj.close()
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# Copy permission bits, access time, etc.
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try:
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_copy_metadata(path, tmp_path)
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except OSError:
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# e.g. the file didn't already exist. Ignore any failure to copy metadata
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pass
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if os.name == 'nt' and os.path.exists(path):
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# Rename over existing file doesn't work on Windows
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os.remove(path)
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os.rename(tmp_path, path)
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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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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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