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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
18from .history import HistoryOutput
20# TODO: Move the various attributes (cache_size, [others now moved]). Some
21# of these are also attributes of InteractiveShell. They should be on ONE object
22# only and the other objects should ask that one object for their values.
24class DisplayHook(Configurable):
25 """The custom IPython displayhook to replace sys.displayhook.
27 This class does many things, but the basic idea is that it is a callable
28 that gets called anytime user code returns a value.
29 """
31 shell = Instance('IPython.core.interactiveshell.InteractiveShellABC',
32 allow_none=True)
33 exec_result = Instance('IPython.core.interactiveshell.ExecutionResult',
34 allow_none=True)
35 cull_fraction = Float(0.2)
37 def __init__(self, shell=None, cache_size=1000, **kwargs):
38 super().__init__(shell=shell, **kwargs)
39 self._is_active = False
40 cache_size_min = 3
41 if cache_size <= 0:
42 self.do_full_cache = 0
43 cache_size = 0
44 elif cache_size < cache_size_min:
45 self.do_full_cache = 0
46 cache_size = 0
47 warn('caching was disabled (min value for cache size is %s).' %
48 cache_size_min,stacklevel=3)
49 else:
50 self.do_full_cache = 1
52 self.cache_size = cache_size
54 # we need a reference to the user-level namespace
55 self.shell = shell
57 self._,self.__,self.___ = '','',''
59 # these are deliberately global:
60 to_user_ns = {'_':self._,'__':self.__,'___':self.___}
61 self.shell.user_ns.update(to_user_ns)
63 @property
64 def prompt_count(self):
65 return self.shell.execution_count - 1
67 #-------------------------------------------------------------------------
68 # Methods used in __call__. Override these methods to modify the behavior
69 # of the displayhook.
70 #-------------------------------------------------------------------------
72 def check_for_underscore(self):
73 """Check if the user has set the '_' variable by hand."""
74 # If something injected a '_' variable in __builtin__, delete
75 # ipython's automatic one so we don't clobber that. gettext() in
76 # particular uses _, so we need to stay away from it.
77 if '_' in builtin_mod.__dict__:
78 try:
79 user_value = self.shell.user_ns['_']
80 if user_value is not self._:
81 return
82 del self.shell.user_ns['_']
83 except KeyError:
84 pass
86 def quiet(self):
87 """Should we silence the display hook because of ';'?"""
88 # do not print output if input ends in ';'
90 try:
91 cell = self.shell.history_manager.input_hist_parsed[-1]
92 except IndexError:
93 # some uses of ipshellembed may fail here
94 return False
96 return self.semicolon_at_end_of_expression(cell)
98 @staticmethod
99 def semicolon_at_end_of_expression(expression):
100 """Parse Python expression and detects whether last token is ';'"""
102 sio = _io.StringIO(expression)
103 tokens = list(tokenize.generate_tokens(sio.readline))
105 for token in reversed(tokens):
106 if token[0] in (tokenize.ENDMARKER, tokenize.NL, tokenize.NEWLINE, tokenize.COMMENT):
107 continue
108 if (token[0] == tokenize.OP) and (token[1] == ';'):
109 return True
110 else:
111 return False
113 def start_displayhook(self):
114 """Start the displayhook, initializing resources."""
115 self._is_active = True
117 @property
118 def is_active(self):
119 return self._is_active
121 def write_output_prompt(self):
122 """Write the output prompt.
124 The default implementation simply writes the prompt to
125 ``sys.stdout``.
126 """
127 # Use write, not print which adds an extra space.
128 sys.stdout.write(self.shell.separate_out)
129 outprompt = f'Out[{self.shell.execution_count - 1}]: '
130 if self.do_full_cache:
131 sys.stdout.write(outprompt)
133 def compute_format_data(self, result):
134 """Compute format data of the object to be displayed.
136 The format data is a generalization of the :func:`repr` of an object.
137 In the default implementation the format data is a :class:`dict` of
138 key value pair where the keys are valid MIME types and the values
139 are JSON'able data structure containing the raw data for that MIME
140 type. It is up to frontends to determine pick a MIME to to use and
141 display that data in an appropriate manner.
143 This method only computes the format data for the object and should
144 NOT actually print or write that to a stream.
146 Parameters
147 ----------
148 result : object
149 The Python object passed to the display hook, whose format will be
150 computed.
152 Returns
153 -------
154 (format_dict, md_dict) : dict
155 format_dict is a :class:`dict` whose keys are valid MIME types and values are
156 JSON'able raw data for that MIME type. It is recommended that
157 all return values of this should always include the "text/plain"
158 MIME type representation of the object.
159 md_dict is a :class:`dict` with the same MIME type keys
160 of metadata associated with each output.
162 """
163 return self.shell.display_formatter.format(result)
165 # This can be set to True by the write_output_prompt method in a subclass
166 prompt_end_newline = False
168 def write_format_data(self, format_dict, md_dict=None) -> None:
169 """Write the format data dict to the frontend.
171 This default version of this method simply writes the plain text
172 representation of the object to ``sys.stdout``. Subclasses should
173 override this method to send the entire `format_dict` to the
174 frontends.
176 Parameters
177 ----------
178 format_dict : dict
179 The format dict for the object passed to `sys.displayhook`.
180 md_dict : dict (optional)
181 The metadata dict to be associated with the display data.
182 """
183 if 'text/plain' not in format_dict:
184 # nothing to do
185 return
186 # We want to print because we want to always make sure we have a
187 # newline, even if all the prompt separators are ''. This is the
188 # standard IPython behavior.
189 result_repr = format_dict['text/plain']
190 if '\n' in result_repr:
191 # So that multi-line strings line up with the left column of
192 # the screen, instead of having the output prompt mess up
193 # their first line.
194 # We use the prompt template instead of the expanded prompt
195 # because the expansion may add ANSI escapes that will interfere
196 # with our ability to determine whether or not we should add
197 # a newline.
198 if not self.prompt_end_newline:
199 # But avoid extraneous empty lines.
200 result_repr = '\n' + result_repr
202 try:
203 print(result_repr)
204 except UnicodeEncodeError:
205 # If a character is not supported by the terminal encoding replace
206 # it with its \u or \x representation
207 print(result_repr.encode(sys.stdout.encoding,'backslashreplace').decode(sys.stdout.encoding))
209 def update_user_ns(self, result):
210 """Update user_ns with various things like _, __, _1, etc."""
212 # Avoid recursive reference when displaying _oh/Out
213 if self.cache_size and result is not self.shell.user_ns['_oh']:
214 if len(self.shell.user_ns['_oh']) >= self.cache_size and self.do_full_cache:
215 self.cull_cache()
217 # Don't overwrite '_' and friends if '_' is in __builtin__
218 # (otherwise we cause buggy behavior for things like gettext). and
219 # do not overwrite _, __ or ___ if one of these has been assigned
220 # by the user.
221 update_unders = True
222 for unders in ['_'*i for i in range(1,4)]:
223 if unders not in self.shell.user_ns:
224 continue
225 if getattr(self, unders) is not self.shell.user_ns.get(unders):
226 update_unders = False
228 self.___ = self.__
229 self.__ = self._
230 self._ = result
232 if ('_' not in builtin_mod.__dict__) and (update_unders):
233 self.shell.push({'_':self._,
234 '__':self.__,
235 '___':self.___}, interactive=False)
237 # hackish access to top-level namespace to create _1,_2... dynamically
238 to_main = {}
239 if self.do_full_cache:
240 new_result = '_%s' % self.prompt_count
241 to_main[new_result] = result
242 self.shell.push(to_main, interactive=False)
243 self.shell.user_ns['_oh'][self.prompt_count] = result
245 def fill_exec_result(self, result):
246 if self.exec_result is not None:
247 self.exec_result.result = result
249 def log_output(self, format_dict):
250 """Log the output."""
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 })