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1"""Displayhook for IPython.
3This defines a callable class that IPython uses for `sys.displayhook`.
4"""
6# Copyright (c) IPython Development Team.
7# Distributed under the terms of the Modified BSD License.
9import builtins as builtin_mod
10import sys
11import io as _io
12import tokenize
14from traitlets.config.configurable import Configurable
15from traitlets import Instance, Float
16from warnings import warn
19# TODO: Move the various attributes (cache_size, [others now moved]). Some
20# of these are also attributes of InteractiveShell. They should be on ONE object
21# only and the other objects should ask that one object for their values.
23class DisplayHook(Configurable):
24 """The custom IPython displayhook to replace sys.displayhook.
26 This class does many things, but the basic idea is that it is a callable
27 that gets called anytime user code returns a value.
28 """
30 shell = Instance('IPython.core.interactiveshell.InteractiveShellABC',
31 allow_none=True)
32 exec_result = Instance('IPython.core.interactiveshell.ExecutionResult',
33 allow_none=True)
34 cull_fraction = Float(0.2)
36 def __init__(self, shell=None, cache_size=1000, **kwargs):
37 super().__init__(shell=shell, **kwargs)
38 self._is_active = False
39 cache_size_min = 3
40 if cache_size <= 0:
41 self.do_full_cache = 0
42 cache_size = 0
43 elif cache_size < cache_size_min:
44 self.do_full_cache = 0
45 cache_size = 0
46 warn('caching was disabled (min value for cache size is %s).' %
47 cache_size_min,stacklevel=3)
48 else:
49 self.do_full_cache = 1
51 self.cache_size = cache_size
53 # we need a reference to the user-level namespace
54 self.shell = shell
56 self._,self.__,self.___ = '','',''
58 # these are deliberately global:
59 to_user_ns = {'_':self._,'__':self.__,'___':self.___}
60 self.shell.user_ns.update(to_user_ns)
62 @property
63 def prompt_count(self):
64 return self.shell.execution_count - 1
66 #-------------------------------------------------------------------------
67 # Methods used in __call__. Override these methods to modify the behavior
68 # of the displayhook.
69 #-------------------------------------------------------------------------
71 def check_for_underscore(self):
72 """Check if the user has set the '_' variable by hand."""
73 # If something injected a '_' variable in __builtin__, delete
74 # ipython's automatic one so we don't clobber that. gettext() in
75 # particular uses _, so we need to stay away from it.
76 if '_' in builtin_mod.__dict__:
77 try:
78 user_value = self.shell.user_ns['_']
79 if user_value is not self._:
80 return
81 del self.shell.user_ns['_']
82 except KeyError:
83 pass
85 def quiet(self):
86 """Should we silence the display hook because of ';'?"""
87 # do not print output if input ends in ';'
89 try:
90 cell = self.shell.history_manager.input_hist_parsed[-1]
91 except IndexError:
92 # some uses of ipshellembed may fail here
93 return False
95 return self.semicolon_at_end_of_expression(cell)
97 @staticmethod
98 def semicolon_at_end_of_expression(expression):
99 """Parse Python expression and detects whether last token is ';'"""
101 sio = _io.StringIO(expression)
102 tokens = list(tokenize.generate_tokens(sio.readline))
104 for token in reversed(tokens):
105 if token[0] in (tokenize.ENDMARKER, tokenize.NL, tokenize.NEWLINE, tokenize.COMMENT):
106 continue
107 if (token[0] == tokenize.OP) and (token[1] == ';'):
108 return True
109 else:
110 return False
112 def start_displayhook(self):
113 """Start the displayhook, initializing resources."""
114 self._is_active = True
116 @property
117 def is_active(self):
118 return self._is_active
120 def write_output_prompt(self):
121 """Write the output prompt.
123 The default implementation simply writes the prompt to
124 ``sys.stdout``.
125 """
126 # Use write, not print which adds an extra space.
127 sys.stdout.write(self.shell.separate_out)
128 outprompt = f'Out[{self.shell.execution_count - 1}]: '
129 if self.do_full_cache:
130 sys.stdout.write(outprompt)
132 def compute_format_data(self, result):
133 """Compute format data of the object to be displayed.
135 The format data is a generalization of the :func:`repr` of an object.
136 In the default implementation the format data is a :class:`dict` of
137 key value pair where the keys are valid MIME types and the values
138 are JSON'able data structure containing the raw data for that MIME
139 type. It is up to frontends to determine pick a MIME to to use and
140 display that data in an appropriate manner.
142 This method only computes the format data for the object and should
143 NOT actually print or write that to a stream.
145 Parameters
146 ----------
147 result : object
148 The Python object passed to the display hook, whose format will be
149 computed.
151 Returns
152 -------
153 (format_dict, md_dict) : dict
154 format_dict is a :class:`dict` whose keys are valid MIME types and values are
155 JSON'able raw data for that MIME type. It is recommended that
156 all return values of this should always include the "text/plain"
157 MIME type representation of the object.
158 md_dict is a :class:`dict` with the same MIME type keys
159 of metadata associated with each output.
161 """
162 return self.shell.display_formatter.format(result)
164 # This can be set to True by the write_output_prompt method in a subclass
165 prompt_end_newline = False
167 def write_format_data(self, format_dict, md_dict=None) -> None:
168 """Write the format data dict to the frontend.
170 This default version of this method simply writes the plain text
171 representation of the object to ``sys.stdout``. Subclasses should
172 override this method to send the entire `format_dict` to the
173 frontends.
175 Parameters
176 ----------
177 format_dict : dict
178 The format dict for the object passed to `sys.displayhook`.
179 md_dict : dict (optional)
180 The metadata dict to be associated with the display data.
181 """
182 if 'text/plain' not in format_dict:
183 # nothing to do
184 return
185 # We want to print because we want to always make sure we have a
186 # newline, even if all the prompt separators are ''. This is the
187 # standard IPython behavior.
188 result_repr = format_dict['text/plain']
189 if '\n' in result_repr:
190 # So that multi-line strings line up with the left column of
191 # the screen, instead of having the output prompt mess up
192 # their first line.
193 # We use the prompt template instead of the expanded prompt
194 # because the expansion may add ANSI escapes that will interfere
195 # with our ability to determine whether or not we should add
196 # a newline.
197 if not self.prompt_end_newline:
198 # But avoid extraneous empty lines.
199 result_repr = '\n' + result_repr
201 try:
202 print(result_repr)
203 except UnicodeEncodeError:
204 # If a character is not supported by the terminal encoding replace
205 # it with its \u or \x representation
206 print(result_repr.encode(sys.stdout.encoding,'backslashreplace').decode(sys.stdout.encoding))
208 def update_user_ns(self, result):
209 """Update user_ns with various things like _, __, _1, etc."""
211 # Avoid recursive reference when displaying _oh/Out
212 if self.cache_size and result is not self.shell.user_ns['_oh']:
213 if len(self.shell.user_ns['_oh']) >= self.cache_size and self.do_full_cache:
214 self.cull_cache()
216 # Don't overwrite '_' and friends if '_' is in __builtin__
217 # (otherwise we cause buggy behavior for things like gettext). and
218 # do not overwrite _, __ or ___ if one of these has been assigned
219 # by the user.
220 update_unders = True
221 for unders in ['_'*i for i in range(1,4)]:
222 if unders not in self.shell.user_ns:
223 continue
224 user_value = self.shell.user_ns[unders]
225 if unders in self.shell.user_ns_hidden:
226 if self.shell.user_ns_hidden[unders] is user_value:
227 continue
228 elif getattr(self, unders) is user_value:
229 continue
230 update_unders = False
232 self.___ = self.__
233 self.__ = self._
234 self._ = result
236 if ('_' not in builtin_mod.__dict__) and (update_unders):
237 self.shell.push({'_':self._,
238 '__':self.__,
239 '___':self.___}, interactive=False)
241 # hackish access to top-level namespace to create _1,_2... dynamically
242 to_main = {}
243 if self.do_full_cache:
244 new_result = '_%s' % self.prompt_count
245 to_main[new_result] = result
246 self.shell.push(to_main, interactive=False)
247 self.shell.user_ns['_oh'][self.prompt_count] = result
249 def fill_exec_result(self, result):
250 if self.exec_result is not None:
251 self.exec_result.result = result
253 def log_output(self, format_dict):
254 """Log the output."""
255 from .history import HistoryOutput
256 self.shell.history_manager.outputs[self.prompt_count].append(
257 HistoryOutput(output_type="execute_result", bundle=format_dict)
258 )
259 if "text/plain" not in format_dict:
260 # nothing to do
261 return
262 if self.shell.logger.log_output:
263 self.shell.logger.log_write(format_dict['text/plain'], 'output')
264 self.shell.history_manager.output_hist_reprs[self.prompt_count] = \
265 format_dict['text/plain']
267 def finish_displayhook(self):
268 """Finish up all displayhook activities."""
269 sys.stdout.write(self.shell.separate_out2)
270 sys.stdout.flush()
271 self._is_active = False
273 def __call__(self, result=None):
274 """Printing with history cache management.
276 This is invoked every time the interpreter needs to print, and is
277 activated by setting the variable sys.displayhook to it.
278 """
279 self.check_for_underscore()
280 if result is not None and not self.quiet():
281 self.start_displayhook()
282 self.write_output_prompt()
283 format_dict, md_dict = self.compute_format_data(result)
284 self.update_user_ns(result)
285 self.fill_exec_result(result)
286 if format_dict:
287 self.write_format_data(format_dict, md_dict)
288 self.log_output(format_dict)
289 self.finish_displayhook()
291 def cull_cache(self):
292 """Output cache is full, cull the oldest entries"""
293 oh = self.shell.user_ns.get('_oh', {})
294 sz = len(oh)
295 cull_count = max(int(sz * self.cull_fraction), 2)
296 warn('Output cache limit (currently {sz} entries) hit.\n'
297 'Flushing oldest {cull_count} entries.'.format(sz=sz, cull_count=cull_count))
299 for i, n in enumerate(sorted(oh)):
300 if i >= cull_count:
301 break
302 self.shell.user_ns.pop('_%i' % n, None)
303 oh.pop(n, None)
305 def flush(self):
306 if not self.do_full_cache:
307 raise ValueError("You shouldn't have reached the cache flush "
308 "if full caching is not enabled!")
309 # delete auto-generated vars from global namespace
311 for n in range(1,self.prompt_count + 1):
312 key = '_'+repr(n)
313 try:
314 del self.shell.user_ns_hidden[key]
315 except KeyError:
316 pass
317 try:
318 del self.shell.user_ns[key]
319 except KeyError:
320 pass
321 # In some embedded circumstances, the user_ns doesn't have the
322 # '_oh' key set up.
323 oh = self.shell.user_ns.get('_oh', None)
324 if oh is not None:
325 oh.clear()
327 # Release our own references to objects:
328 self._, self.__, self.___ = '', '', ''
330 if '_' not in builtin_mod.__dict__:
331 self.shell.user_ns.update({'_':self._,'__':self.__,'___':self.___})
332 import gc
333 # TODO: Is this really needed?
334 # IronPython blocks here forever
335 if sys.platform != "cli":
336 gc.collect()
339class CapturingDisplayHook:
340 def __init__(self, shell, outputs=None):
341 self.shell = shell
342 if outputs is None:
343 outputs = []
344 self.outputs = outputs
346 def __call__(self, result=None):
347 if result is None:
348 return
349 format_dict, md_dict = self.shell.display_formatter.format(result)
350 self.outputs.append({ 'data': format_dict, 'metadata': md_dict })