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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 if getattr(self, unders) is not self.shell.user_ns.get(unders):
225 update_unders = False
227 self.___ = self.__
228 self.__ = self._
229 self._ = result
231 if ('_' not in builtin_mod.__dict__) and (update_unders):
232 self.shell.push({'_':self._,
233 '__':self.__,
234 '___':self.___}, interactive=False)
236 # hackish access to top-level namespace to create _1,_2... dynamically
237 to_main = {}
238 if self.do_full_cache:
239 new_result = '_%s' % self.prompt_count
240 to_main[new_result] = result
241 self.shell.push(to_main, interactive=False)
242 self.shell.user_ns['_oh'][self.prompt_count] = result
244 def fill_exec_result(self, result):
245 if self.exec_result is not None:
246 self.exec_result.result = result
248 def log_output(self, format_dict):
249 """Log the output."""
250 from .history import HistoryOutput
251 self.shell.history_manager.outputs[self.prompt_count].append(
252 HistoryOutput(output_type="execute_result", bundle=format_dict)
253 )
254 if "text/plain" not in format_dict:
255 # nothing to do
256 return
257 if self.shell.logger.log_output:
258 self.shell.logger.log_write(format_dict['text/plain'], 'output')
259 self.shell.history_manager.output_hist_reprs[self.prompt_count] = \
260 format_dict['text/plain']
262 def finish_displayhook(self):
263 """Finish up all displayhook activities."""
264 sys.stdout.write(self.shell.separate_out2)
265 sys.stdout.flush()
266 self._is_active = False
268 def __call__(self, result=None):
269 """Printing with history cache management.
271 This is invoked every time the interpreter needs to print, and is
272 activated by setting the variable sys.displayhook to it.
273 """
274 self.check_for_underscore()
275 if result is not None and not self.quiet():
276 self.start_displayhook()
277 self.write_output_prompt()
278 format_dict, md_dict = self.compute_format_data(result)
279 self.update_user_ns(result)
280 self.fill_exec_result(result)
281 if format_dict:
282 self.write_format_data(format_dict, md_dict)
283 self.log_output(format_dict)
284 self.finish_displayhook()
286 def cull_cache(self):
287 """Output cache is full, cull the oldest entries"""
288 oh = self.shell.user_ns.get('_oh', {})
289 sz = len(oh)
290 cull_count = max(int(sz * self.cull_fraction), 2)
291 warn('Output cache limit (currently {sz} entries) hit.\n'
292 'Flushing oldest {cull_count} entries.'.format(sz=sz, cull_count=cull_count))
294 for i, n in enumerate(sorted(oh)):
295 if i >= cull_count:
296 break
297 self.shell.user_ns.pop('_%i' % n, None)
298 oh.pop(n, None)
300 def flush(self):
301 if not self.do_full_cache:
302 raise ValueError("You shouldn't have reached the cache flush "
303 "if full caching is not enabled!")
304 # delete auto-generated vars from global namespace
306 for n in range(1,self.prompt_count + 1):
307 key = '_'+repr(n)
308 try:
309 del self.shell.user_ns_hidden[key]
310 except KeyError:
311 pass
312 try:
313 del self.shell.user_ns[key]
314 except KeyError:
315 pass
316 # In some embedded circumstances, the user_ns doesn't have the
317 # '_oh' key set up.
318 oh = self.shell.user_ns.get('_oh', None)
319 if oh is not None:
320 oh.clear()
322 # Release our own references to objects:
323 self._, self.__, self.___ = '', '', ''
325 if '_' not in builtin_mod.__dict__:
326 self.shell.user_ns.update({'_':self._,'__':self.__,'___':self.___})
327 import gc
328 # TODO: Is this really needed?
329 # IronPython blocks here forever
330 if sys.platform != "cli":
331 gc.collect()
334class CapturingDisplayHook:
335 def __init__(self, shell, outputs=None):
336 self.shell = shell
337 if outputs is None:
338 outputs = []
339 self.outputs = outputs
341 def __call__(self, result=None):
342 if result is None:
343 return
344 format_dict, md_dict = self.shell.display_formatter.format(result)
345 self.outputs.append({ 'data': format_dict, 'metadata': md_dict })