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# -*- coding: utf-8 -*-
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"""Displayhook for IPython.
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This defines a callable class that IPython uses for `sys.displayhook`.
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"""
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# Copyright (c) IPython Development Team.
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# Distributed under the terms of the Modified BSD License.
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import builtins as builtin_mod
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import sys
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import io as _io
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import tokenize
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from traitlets.config.configurable import Configurable
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from traitlets import Instance, Float
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from warnings import warn
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# TODO: Move the various attributes (cache_size, [others now moved]). Some
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# of these are also attributes of InteractiveShell. They should be on ONE object
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# only and the other objects should ask that one object for their values.
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class DisplayHook(Configurable):
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"""The custom IPython displayhook to replace sys.displayhook.
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This class does many things, but the basic idea is that it is a callable
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that gets called anytime user code returns a value.
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"""
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shell = Instance('IPython.core.interactiveshell.InteractiveShellABC',
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allow_none=True)
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exec_result = Instance('IPython.core.interactiveshell.ExecutionResult',
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allow_none=True)
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cull_fraction = Float(0.2)
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def __init__(self, shell=None, cache_size=1000, **kwargs):
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super(DisplayHook, self).__init__(shell=shell, **kwargs)
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cache_size_min = 3
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if cache_size <= 0:
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self.do_full_cache = 0
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cache_size = 0
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elif cache_size < cache_size_min:
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self.do_full_cache = 0
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cache_size = 0
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warn('caching was disabled (min value for cache size is %s).' %
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cache_size_min,stacklevel=3)
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else:
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self.do_full_cache = 1
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self.cache_size = cache_size
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# we need a reference to the user-level namespace
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self.shell = shell
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self._,self.__,self.___ = '','',''
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# these are deliberately global:
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to_user_ns = {'_':self._,'__':self.__,'___':self.___}
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self.shell.user_ns.update(to_user_ns)
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@property
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def prompt_count(self):
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return self.shell.execution_count
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#-------------------------------------------------------------------------
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# Methods used in __call__. Override these methods to modify the behavior
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# of the displayhook.
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#-------------------------------------------------------------------------
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def check_for_underscore(self):
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"""Check if the user has set the '_' variable by hand."""
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# If something injected a '_' variable in __builtin__, delete
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# ipython's automatic one so we don't clobber that. gettext() in
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# particular uses _, so we need to stay away from it.
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if '_' in builtin_mod.__dict__:
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try:
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user_value = self.shell.user_ns['_']
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if user_value is not self._:
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return
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del self.shell.user_ns['_']
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except KeyError:
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pass
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def quiet(self):
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"""Should we silence the display hook because of ';'?"""
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# do not print output if input ends in ';'
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try:
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cell = self.shell.history_manager.input_hist_parsed[-1]
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except IndexError:
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# some uses of ipshellembed may fail here
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return False
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return self.semicolon_at_end_of_expression(cell)
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@staticmethod
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def semicolon_at_end_of_expression(expression):
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"""Parse Python expression and detects whether last token is ';'"""
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sio = _io.StringIO(expression)
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tokens = list(tokenize.generate_tokens(sio.readline))
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for token in reversed(tokens):
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if token[0] in (tokenize.ENDMARKER, tokenize.NL, tokenize.NEWLINE, tokenize.COMMENT):
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continue
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if (token[0] == tokenize.OP) and (token[1] == ';'):
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return True
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else:
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return False
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def start_displayhook(self):
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"""Start the displayhook, initializing resources."""
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pass
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def write_output_prompt(self):
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"""Write the output prompt.
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The default implementation simply writes the prompt to
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``sys.stdout``.
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"""
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# Use write, not print which adds an extra space.
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sys.stdout.write(self.shell.separate_out)
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outprompt = 'Out[{}]: '.format(self.shell.execution_count)
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if self.do_full_cache:
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sys.stdout.write(outprompt)
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def compute_format_data(self, result):
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"""Compute format data of the object to be displayed.
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The format data is a generalization of the :func:`repr` of an object.
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In the default implementation the format data is a :class:`dict` of
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key value pair where the keys are valid MIME types and the values
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are JSON'able data structure containing the raw data for that MIME
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type. It is up to frontends to determine pick a MIME to to use and
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display that data in an appropriate manner.
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This method only computes the format data for the object and should
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NOT actually print or write that to a stream.
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Parameters
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----------
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result : object
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The Python object passed to the display hook, whose format will be
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computed.
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Returns
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-------
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(format_dict, md_dict) : dict
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format_dict is a :class:`dict` whose keys are valid MIME types and values are
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JSON'able raw data for that MIME type. It is recommended that
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all return values of this should always include the "text/plain"
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MIME type representation of the object.
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md_dict is a :class:`dict` with the same MIME type keys
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of metadata associated with each output.
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"""
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return self.shell.display_formatter.format(result)
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# This can be set to True by the write_output_prompt method in a subclass
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prompt_end_newline = False
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def write_format_data(self, format_dict, md_dict=None) -> None:
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"""Write the format data dict to the frontend.
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This default version of this method simply writes the plain text
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representation of the object to ``sys.stdout``. Subclasses should
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override this method to send the entire `format_dict` to the
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frontends.
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Parameters
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----------
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format_dict : dict
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The format dict for the object passed to `sys.displayhook`.
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md_dict : dict (optional)
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The metadata dict to be associated with the display data.
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"""
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if 'text/plain' not in format_dict:
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# nothing to do
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return
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# We want to print because we want to always make sure we have a
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# newline, even if all the prompt separators are ''. This is the
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# standard IPython behavior.
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result_repr = format_dict['text/plain']
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if '\n' in result_repr:
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# So that multi-line strings line up with the left column of
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# the screen, instead of having the output prompt mess up
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# their first line.
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# We use the prompt template instead of the expanded prompt
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# because the expansion may add ANSI escapes that will interfere
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# with our ability to determine whether or not we should add
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# a newline.
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if not self.prompt_end_newline:
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# But avoid extraneous empty lines.
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result_repr = '\n' + result_repr
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try:
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print(result_repr)
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except UnicodeEncodeError:
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# If a character is not supported by the terminal encoding replace
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# it with its \u or \x representation
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print(result_repr.encode(sys.stdout.encoding,'backslashreplace').decode(sys.stdout.encoding))
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def update_user_ns(self, result):
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"""Update user_ns with various things like _, __, _1, etc."""
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# Avoid recursive reference when displaying _oh/Out
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if self.cache_size and result is not self.shell.user_ns['_oh']:
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if len(self.shell.user_ns['_oh']) >= self.cache_size and self.do_full_cache:
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self.cull_cache()
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# Don't overwrite '_' and friends if '_' is in __builtin__
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# (otherwise we cause buggy behavior for things like gettext). and
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# do not overwrite _, __ or ___ if one of these has been assigned
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# by the user.
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update_unders = True
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for unders in ['_'*i for i in range(1,4)]:
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if unders not in self.shell.user_ns:
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continue
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if getattr(self, unders) is not self.shell.user_ns.get(unders):
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update_unders = False
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self.___ = self.__
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self.__ = self._
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self._ = result
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if ('_' not in builtin_mod.__dict__) and (update_unders):
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self.shell.push({'_':self._,
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'__':self.__,
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'___':self.___}, interactive=False)
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# hackish access to top-level namespace to create _1,_2... dynamically
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to_main = {}
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if self.do_full_cache:
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new_result = '_%s' % self.prompt_count
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to_main[new_result] = result
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self.shell.push(to_main, interactive=False)
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self.shell.user_ns['_oh'][self.prompt_count] = result
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def fill_exec_result(self, result):
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if self.exec_result is not None:
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self.exec_result.result = result
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def log_output(self, format_dict):
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"""Log the output."""
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if 'text/plain' not in format_dict:
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# nothing to do
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return
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if self.shell.logger.log_output:
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self.shell.logger.log_write(format_dict['text/plain'], 'output')
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self.shell.history_manager.output_hist_reprs[self.prompt_count] = \
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format_dict['text/plain']
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def finish_displayhook(self):
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"""Finish up all displayhook activities."""
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sys.stdout.write(self.shell.separate_out2)
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sys.stdout.flush()
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def __call__(self, result=None):
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"""Printing with history cache management.
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This is invoked every time the interpreter needs to print, and is
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activated by setting the variable sys.displayhook to it.
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"""
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self.check_for_underscore()
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if result is not None and not self.quiet():
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self.start_displayhook()
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self.write_output_prompt()
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format_dict, md_dict = self.compute_format_data(result)
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self.update_user_ns(result)
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self.fill_exec_result(result)
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if format_dict:
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self.write_format_data(format_dict, md_dict)
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self.log_output(format_dict)
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self.finish_displayhook()
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def cull_cache(self):
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"""Output cache is full, cull the oldest entries"""
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oh = self.shell.user_ns.get('_oh', {})
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sz = len(oh)
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cull_count = max(int(sz * self.cull_fraction), 2)
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warn('Output cache limit (currently {sz} entries) hit.\n'
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'Flushing oldest {cull_count} entries.'.format(sz=sz, cull_count=cull_count))
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for i, n in enumerate(sorted(oh)):
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if i >= cull_count:
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break
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self.shell.user_ns.pop('_%i' % n, None)
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oh.pop(n, None)
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def flush(self):
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if not self.do_full_cache:
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raise ValueError("You shouldn't have reached the cache flush "
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"if full caching is not enabled!")
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# delete auto-generated vars from global namespace
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for n in range(1,self.prompt_count + 1):
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key = '_'+repr(n)
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try:
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del self.shell.user_ns_hidden[key]
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except KeyError:
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pass
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try:
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del self.shell.user_ns[key]
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except KeyError:
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pass
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# In some embedded circumstances, the user_ns doesn't have the
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# '_oh' key set up.
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oh = self.shell.user_ns.get('_oh', None)
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if oh is not None:
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oh.clear()
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# Release our own references to objects:
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self._, self.__, self.___ = '', '', ''
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if '_' not in builtin_mod.__dict__:
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self.shell.user_ns.update({'_':self._,'__':self.__,'___':self.___})
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import gc
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# TODO: Is this really needed?
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# IronPython blocks here forever
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if sys.platform != "cli":
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gc.collect()
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class CapturingDisplayHook(object):
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def __init__(self, shell, outputs=None):
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self.shell = shell
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if outputs is None:
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outputs = []
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self.outputs = outputs
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def __call__(self, result=None):
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if result is None:
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return
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format_dict, md_dict = self.shell.display_formatter.format(result)
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self.outputs.append({ 'data': format_dict, 'metadata': md_dict })
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