Some documentations about custom formatters (#14579)

IPython/core/formatters.py

@@ -1,1031 +1,1090
 # -*- coding: utf-8 -*-
 """Display formatters.
 
+This module defines the base instances in order to implement custom
+formatters/mimetypes
+got objects:
+
+As we want to see internal IPython working we are going to use the following
+function to diaply objects instead of the normal print or display method:
+
+    >>> ip = get_ipython()
+    >>> ip.display_formatter.format(...)
+    ({'text/plain': 'Ellipsis'}, {})
+
+This return a tuple with the mimebumdle for the current object, and the
+associated metadata.
+
+
+We can now define our own formatter and register it:
+
+
+    >>> from IPython.core.formatters import BaseFormatter, FormatterABC
+
+
+    >>> class LLMFormatter(BaseFormatter):
+    ...
+    ...     format_type = 'x-vendor/llm'
+    ...     print_method = '_repr_llm_'
+    ...     _return_type = (dict, str)
+
+    >>> llm_formatter = LLMFormatter(parent=ip.display_formatter)
+
+    >>> ip.display_formatter.formatters[LLMFormatter.format_type] = llm_formatter
+
+Now any class that define `_repr_llm_` will return a x-vendor/llm as part of
+it's display data:
+
+    >>> class A:
+    ...
+    ...     def _repr_llm_(self, *kwargs):
+    ...         return 'This a A'
+    ...
+
+    >>> ip.display_formatter.format(A())
+    ({'text/plain': '<IPython.core.formatters.A at ...>', 'x-vendor/llm': 'This a A'}, {})
+
+As usual, you can register methods for third party types (see
+:ref:`third_party_formatting`)
+
+    >>> def llm_int(obj):
+    ...      return 'This is the integer %s, in between %s and %s'%(obj, obj-1, obj+1)
+
+    >>> llm_formatter.for_type(int, llm_int)
+
+    >>> ip.display_formatter.format(42)
+    ({'text/plain': '42', 'x-vendor/llm': 'This is the integer 42, in between 41 and 43'}, {})
+
+
 Inheritance diagram:
 
 .. inheritance-diagram:: IPython.core.formatters
    :parts: 3
 """
 
 # Copyright (c) IPython Development Team.
 # Distributed under the terms of the Modified BSD License.
 
 import abc
 import sys
 import traceback
 import warnings
 from io import StringIO
 
 from decorator import decorator
 
 from traitlets.config.configurable import Configurable
 from .getipython import get_ipython
 from ..utils.sentinel import Sentinel
 from ..utils.dir2 import get_real_method
 from ..lib import pretty
 from traitlets import (
     Bool, Dict, Integer, Unicode, CUnicode, ObjectName, List,
     ForwardDeclaredInstance,
     default, observe,
 )
 
 from typing import Any
 
 
 class DisplayFormatter(Configurable):
 
     active_types = List(Unicode(),
         help="""List of currently active mime-types to display.
         You can use this to set a white-list for formats to display.
-        
+
         Most users will not need to change this value.
-        """).tag(config=True)
+        """,
+    ).tag(config=True)
 
     @default('active_types')
     def _active_types_default(self):
         return self.format_types
 
     @observe('active_types')
     def _active_types_changed(self, change):
         for key, formatter in self.formatters.items():
             if key in change['new']:
                 formatter.enabled = True
             else:
                 formatter.enabled = False
 
     ipython_display_formatter = ForwardDeclaredInstance("FormatterABC")  # type: ignore
 
     @default("ipython_display_formatter")
     def _default_formatter(self):
         return IPythonDisplayFormatter(parent=self)
 
     mimebundle_formatter = ForwardDeclaredInstance("FormatterABC")  # type: ignore
 
     @default("mimebundle_formatter")
     def _default_mime_formatter(self):
         return MimeBundleFormatter(parent=self)
 
     # A dict of formatter whose keys are format types (MIME types) and whose
     # values are subclasses of BaseFormatter.
     formatters = Dict()
 
     @default("formatters")
     def _formatters_default(self):
         """Activate the default formatters."""
         formatter_classes = [
             PlainTextFormatter,
             HTMLFormatter,
             MarkdownFormatter,
             SVGFormatter,
             PNGFormatter,
             PDFFormatter,
             JPEGFormatter,
             LatexFormatter,
             JSONFormatter,
             JavascriptFormatter
         ]
         d = {}
         for cls in formatter_classes:
             f = cls(parent=self)
             d[f.format_type] = f
         return d
 
     def format(self, obj, include=None, exclude=None):
         """Return a format data dict for an object.
 
         By default all format types will be computed.
 
         The following MIME types are usually implemented:
 
         * text/plain
         * text/html
         * text/markdown
         * text/latex
         * application/json
         * application/javascript
         * application/pdf
         * image/png
         * image/jpeg
         * image/svg+xml
 
         Parameters
         ----------
         obj : object
             The Python object whose format data will be computed.
         include : list, tuple or set; optional
             A list of format type strings (MIME types) to include in the
             format data dict. If this is set *only* the format types included
             in this list will be computed.
         exclude : list, tuple or set; optional
             A list of format type string (MIME types) to exclude in the format
             data dict. If this is set all format types will be computed,
             except for those included in this argument.
             Mimetypes present in exclude will take precedence over the ones in include
 
         Returns
         -------
         (format_dict, metadata_dict) : tuple of two dicts
             format_dict is a dictionary of key/value pairs, one of each format that was
             generated for the object. The keys are the format types, which
             will usually be MIME type strings and the values and JSON'able
             data structure containing the raw data for the representation in
             that format.
 
             metadata_dict is a dictionary of metadata about each mime-type output.
             Its keys will be a strict subset of the keys in format_dict.
 
         Notes
         -----
             If an object implement `_repr_mimebundle_` as well as various
             `_repr_*_`, the data returned by `_repr_mimebundle_` will take
             precedence and the corresponding `_repr_*_` for this mimetype will
             not be called.
 
         """
         format_dict = {}
         md_dict = {}
-        
+
         if self.ipython_display_formatter(obj):
             # object handled itself, don't proceed
             return {}, {}
 
         format_dict, md_dict = self.mimebundle_formatter(obj, include=include, exclude=exclude)
 
         if format_dict or md_dict:
             if include:
                 format_dict = {k:v for k,v in format_dict.items() if k in include}
                 md_dict = {k:v for k,v in md_dict.items() if k in include}
             if exclude:
                 format_dict = {k:v for k,v in format_dict.items() if k not in exclude}
                 md_dict = {k:v for k,v in md_dict.items() if k not in exclude}
 
         for format_type, formatter in self.formatters.items():
             if format_type in format_dict:
                 # already got it from mimebundle, maybe don't render again.
                 # exception: manually registered per-mime renderer
                 # check priority:
                 # 1. user-registered per-mime formatter
                 # 2. mime-bundle (user-registered or repr method)
                 # 3. default per-mime formatter (e.g. repr method)
                 try:
                     formatter.lookup(obj)
                 except KeyError:
                     # no special formatter, use mime-bundle-provided value
                     continue
             if include and format_type not in include:
                 continue
             if exclude and format_type in exclude:
                 continue
-            
+
             md = None
             try:
                 data = formatter(obj)
             except:
                 # FIXME: log the exception
                 raise
-            
+
             # formatters can return raw data or (data, metadata)
             if isinstance(data, tuple) and len(data) == 2:
                 data, md = data
-            
+
             if data is not None:
                 format_dict[format_type] = data
             if md is not None:
                 md_dict[format_type] = md
         return format_dict, md_dict
 
     @property
     def format_types(self):
         """Return the format types (MIME types) of the active formatters."""
         return list(self.formatters.keys())
 
 
 #-----------------------------------------------------------------------------
 # Formatters for specific format types (text, html, svg, etc.)
 #-----------------------------------------------------------------------------
 
 
 def _safe_repr(obj):
     """Try to return a repr of an object
 
     always returns a string, at least.
     """
     try:
         return repr(obj)
     except Exception as e:
         return "un-repr-able object (%r)" % e
 
 
 class FormatterWarning(UserWarning):
     """Warning class for errors in formatters"""
 
 @decorator
 def catch_format_error(method, self, *args, **kwargs):
     """show traceback on failed format call"""
     try:
         r = method(self, *args, **kwargs)
     except NotImplementedError:
         # don't warn on NotImplementedErrors
         return self._check_return(None, args[0])
     except Exception:
         exc_info = sys.exc_info()
         ip = get_ipython()
         if ip is not None:
             ip.showtraceback(exc_info)
         else:
             traceback.print_exception(*exc_info)
         return self._check_return(None, args[0])
     return self._check_return(r, args[0])
 
 
 class FormatterABC(metaclass=abc.ABCMeta):
     """ Abstract base class for Formatters.
 
     A formatter is a callable class that is responsible for computing the
     raw format data for a particular format type (MIME type). For example,
     an HTML formatter would have a format type of `text/html` and would return
     the HTML representation of the object when called.
     """
 
     # The format type of the data returned, usually a MIME type.
     format_type = 'text/plain'
 
     # Is the formatter enabled...
     enabled = True
-    
+
     @abc.abstractmethod
     def __call__(self, obj):
         """Return a JSON'able representation of the object.
 
         If the object cannot be formatted by this formatter,
         warn and return None.
         """
         return repr(obj)
 
 
 def _mod_name_key(typ):
     """Return a (__module__, __name__) tuple for a type.
 
     Used as key in Formatter.deferred_printers.
     """
     module = getattr(typ, '__module__', None)
     name = getattr(typ, '__name__', None)
     return (module, name)
 
 
 def _get_type(obj):
     """Return the type of an instance (old and new-style)"""
     return getattr(obj, '__class__', None) or type(obj)
 
 
-_raise_key_error = Sentinel('_raise_key_error', __name__, 
-"""
+_raise_key_error = Sentinel(
+    "_raise_key_error",
+    __name__,
+    """
 Special value to raise a KeyError
 
 Raise KeyError in `BaseFormatter.pop` if passed as the default value to `pop`
-""")
+""",
+)
 
 
 class BaseFormatter(Configurable):
     """A base formatter class that is configurable.
 
     This formatter should usually be used as the base class of all formatters.
     It is a traited :class:`Configurable` class and includes an extensible
     API for users to determine how their objects are formatted. The following
     logic is used to find a function to format an given object.
 
     1. The object is introspected to see if it has a method with the name
        :attr:`print_method`. If is does, that object is passed to that method
        for formatting.
     2. If no print method is found, three internal dictionaries are consulted
        to find print method: :attr:`singleton_printers`, :attr:`type_printers`
        and :attr:`deferred_printers`.
 
     Users should use these dictionaries to register functions that will be
     used to compute the format data for their objects (if those objects don't
     have the special print methods). The easiest way of using these
     dictionaries is through the :meth:`for_type` and :meth:`for_type_by_name`
     methods.
 
     If no function/callable is found to compute the format data, ``None`` is
     returned and this format type is not used.
     """
 
     format_type = Unicode("text/plain")
     _return_type: Any = str
 
     enabled = Bool(True).tag(config=True)
 
     print_method = ObjectName('__repr__')
 
     # The singleton printers.
     # Maps the IDs of the builtin singleton objects to the format functions.
     singleton_printers = Dict().tag(config=True)
 
     # The type-specific printers.
     # Map type objects to the format functions.
     type_printers = Dict().tag(config=True)
 
     # The deferred-import type-specific printers.
     # Map (modulename, classname) pairs to the format functions.
     deferred_printers = Dict().tag(config=True)
-    
+
     @catch_format_error
     def __call__(self, obj):
         """Compute the format for an object."""
         if self.enabled:
             # lookup registered printer
             try:
                 printer = self.lookup(obj)
             except KeyError:
                 pass
             else:
                 return printer(obj)
             # Finally look for special method names
             method = get_real_method(obj, self.print_method)
             if method is not None:
                 return method()
             return None
         else:
             return None
-    
+
     def __contains__(self, typ):
         """map in to lookup_by_type"""
         try:
             self.lookup_by_type(typ)
         except KeyError:
             return False
         else:
             return True
-    
+
     def _check_return(self, r, obj):
         """Check that a return value is appropriate
 
         Return the value if so, None otherwise, warning if invalid.
         """
         if r is None or isinstance(r, self._return_type) or \
             (isinstance(r, tuple) and r and isinstance(r[0], self._return_type)):
             return r
         else:
             warnings.warn(
                 "%s formatter returned invalid type %s (expected %s) for object: %s" % \
                 (self.format_type, type(r), self._return_type, _safe_repr(obj)),
                 FormatterWarning
             )
-    
+
     def lookup(self, obj):
         """Look up the formatter for a given instance.
 
         Parameters
         ----------
         obj : object instance
 
         Returns
         -------
         f : callable
             The registered formatting callable for the type.
 
         Raises
         ------
         KeyError if the type has not been registered.
         """
         # look for singleton first
         obj_id = id(obj)
         if obj_id in self.singleton_printers:
             return self.singleton_printers[obj_id]
         # then lookup by type
         return self.lookup_by_type(_get_type(obj))
-    
+
     def lookup_by_type(self, typ):
         """Look up the registered formatter for a type.
 
         Parameters
         ----------
         typ : type or '__module__.__name__' string for a type
 
         Returns
         -------
         f : callable
             The registered formatting callable for the type.
 
         Raises
         ------
         KeyError if the type has not been registered.
         """
         if isinstance(typ, str):
             typ_key = tuple(typ.rsplit('.',1))
             if typ_key not in self.deferred_printers:
                 # We may have it cached in the type map. We will have to
                 # iterate over all of the types to check.
                 for cls in self.type_printers:
                     if _mod_name_key(cls) == typ_key:
                         return self.type_printers[cls]
             else:
                 return self.deferred_printers[typ_key]
         else:
             for cls in pretty._get_mro(typ):
                 if cls in self.type_printers or self._in_deferred_types(cls):
                     return self.type_printers[cls]
-        
+
         # If we have reached here, the lookup failed.
         raise KeyError("No registered printer for {0!r}".format(typ))
 
     def for_type(self, typ, func=None):
         """Add a format function for a given type.
 
         Parameters
         ----------
         typ : type or '__module__.__name__' string for a type
             The class of the object that will be formatted using `func`.
 
         func : callable
             A callable for computing the format data.
             `func` will be called with the object to be formatted,
             and will return the raw data in this formatter's format.
             Subclasses may use a different call signature for the
             `func` argument.
 
             If `func` is None or not specified, there will be no change,
             only returning the current value.
 
         Returns
         -------
         oldfunc : callable
             The currently registered callable.
             If you are registering a new formatter,
             this will be the previous value (to enable restoring later).
         """
         # if string given, interpret as 'pkg.module.class_name'
         if isinstance(typ, str):
             type_module, type_name = typ.rsplit('.', 1)
             return self.for_type_by_name(type_module, type_name, func)
-        
+
         try:
             oldfunc = self.lookup_by_type(typ)
         except KeyError:
             oldfunc = None
-        
+
         if func is not None:
             self.type_printers[typ] = func
-        
+
         return oldfunc
 
     def for_type_by_name(self, type_module, type_name, func=None):
         """Add a format function for a type specified by the full dotted
         module and name of the type, rather than the type of the object.
 
         Parameters
         ----------
         type_module : str
             The full dotted name of the module the type is defined in, like
             ``numpy``.
 
         type_name : str
             The name of the type (the class name), like ``dtype``
 
         func : callable
             A callable for computing the format data.
             `func` will be called with the object to be formatted,
             and will return the raw data in this formatter's format.
             Subclasses may use a different call signature for the
             `func` argument.
 
             If `func` is None or unspecified, there will be no change,
             only returning the current value.
 
         Returns
         -------
         oldfunc : callable
             The currently registered callable.
             If you are registering a new formatter,
             this will be the previous value (to enable restoring later).
         """
         key = (type_module, type_name)
-        
+
         try:
             oldfunc = self.lookup_by_type("%s.%s" % key)
         except KeyError:
             oldfunc = None
-        
+
         if func is not None:
             self.deferred_printers[key] = func
         return oldfunc
-    
+
     def pop(self, typ, default=_raise_key_error):
         """Pop a formatter for the given type.
 
         Parameters
         ----------
         typ : type or '__module__.__name__' string for a type
         default : object
             value to be returned if no formatter is registered for typ.
 
         Returns
         -------
         obj : object
             The last registered object for the type.
 
         Raises
         ------
         KeyError if the type is not registered and default is not specified.
         """
-        
+
         if isinstance(typ, str):
             typ_key = tuple(typ.rsplit('.',1))
             if typ_key not in self.deferred_printers:
                 # We may have it cached in the type map. We will have to
                 # iterate over all of the types to check.
                 for cls in self.type_printers:
                     if _mod_name_key(cls) == typ_key:
                         old = self.type_printers.pop(cls)
                         break
                 else:
                     old = default
             else:
                 old = self.deferred_printers.pop(typ_key)
         else:
             if typ in self.type_printers:
                 old = self.type_printers.pop(typ)
             else:
                 old = self.deferred_printers.pop(_mod_name_key(typ), default)
         if old is _raise_key_error:
             raise KeyError("No registered value for {0!r}".format(typ))
         return old
 
     def _in_deferred_types(self, cls):
         """
         Check if the given class is specified in the deferred type registry.
 
         Successful matches will be moved to the regular type registry for future use.
         """
         mod = getattr(cls, '__module__', None)
         name = getattr(cls, '__name__', None)
         key = (mod, name)
         if key in self.deferred_printers:
             # Move the printer over to the regular registry.
             printer = self.deferred_printers.pop(key)
             self.type_printers[cls] = printer
             return True
         return False
 
 
 class PlainTextFormatter(BaseFormatter):
     """The default pretty-printer.
 
     This uses :mod:`IPython.lib.pretty` to compute the format data of
     the object. If the object cannot be pretty printed, :func:`repr` is used.
     See the documentation of :mod:`IPython.lib.pretty` for details on
     how to write pretty printers.  Here is a simple example::
 
         def dtype_pprinter(obj, p, cycle):
             if cycle:
                 return p.text('dtype(...)')
             if hasattr(obj, 'fields'):
                 if obj.fields is None:
                     p.text(repr(obj))
                 else:
                     p.begin_group(7, 'dtype([')
                     for i, field in enumerate(obj.descr):
                         if i > 0:
                             p.text(',')
                             p.breakable()
                         p.pretty(field)
                     p.end_group(7, '])')
     """
 
     # The format type of data returned.
     format_type = Unicode('text/plain')
 
     # This subclass ignores this attribute as it always need to return
     # something.
     enabled = Bool(True).tag(config=False)
-    
+
     max_seq_length = Integer(pretty.MAX_SEQ_LENGTH,
         help="""Truncate large collections (lists, dicts, tuples, sets) to this size.
-        
+
         Set to 0 to disable truncation.
-        """
+        """,
     ).tag(config=True)
-    
+
     # Look for a _repr_pretty_ methods to use for pretty printing.
     print_method = ObjectName('_repr_pretty_')
 
     # Whether to pretty-print or not.
     pprint = Bool(True).tag(config=True)
 
     # Whether to be verbose or not.
     verbose = Bool(False).tag(config=True)
 
     # The maximum width.
     max_width = Integer(79).tag(config=True)
 
     # The newline character.
     newline = Unicode('\n').tag(config=True)
 
     # format-string for pprinting floats
     float_format = Unicode('%r')
     # setter for float precision, either int or direct format-string
     float_precision = CUnicode('').tag(config=True)
 
     @observe('float_precision')
     def _float_precision_changed(self, change):
         """float_precision changed, set float_format accordingly.
 
         float_precision can be set by int or str.
         This will set float_format, after interpreting input.
         If numpy has been imported, numpy print precision will also be set.
 
         integer `n` sets format to '%.nf', otherwise, format set directly.
 
         An empty string returns to defaults (repr for float, 8 for numpy).
 
         This parameter can be set via the '%precision' magic.
         """
         new = change['new']
         if '%' in new:
             # got explicit format string
             fmt = new
             try:
                 fmt%3.14159
             except Exception as e:
                 raise ValueError("Precision must be int or format string, not %r"%new) from e
         elif new:
             # otherwise, should be an int
             try:
                 i = int(new)
                 assert i >= 0
             except ValueError as e:
                 raise ValueError("Precision must be int or format string, not %r"%new) from e
             except AssertionError as e:
                 raise ValueError("int precision must be non-negative, not %r"%i) from e
 
             fmt = '%%.%if'%i
             if 'numpy' in sys.modules:
                 # set numpy precision if it has been imported
                 import numpy
                 numpy.set_printoptions(precision=i)
         else:
             # default back to repr
             fmt = '%r'
             if 'numpy' in sys.modules:
                 import numpy
                 # numpy default is 8
                 numpy.set_printoptions(precision=8)
         self.float_format = fmt
 
     # Use the default pretty printers from IPython.lib.pretty.
     @default('singleton_printers')
     def _singleton_printers_default(self):
         return pretty._singleton_pprinters.copy()
 
     @default('type_printers')
     def _type_printers_default(self):
         d = pretty._type_pprinters.copy()
         d[float] = lambda obj,p,cycle: p.text(self.float_format%obj)
         # if NumPy is used, set precision for its float64 type
         if "numpy" in sys.modules:
             import numpy
 
             d[numpy.float64] = lambda obj, p, cycle: p.text(self.float_format % obj)
         return d
 
     @default('deferred_printers')
     def _deferred_printers_default(self):
         return pretty._deferred_type_pprinters.copy()
 
     #### FormatterABC interface ####
 
     @catch_format_error
     def __call__(self, obj):
         """Compute the pretty representation of the object."""
         if not self.pprint:
             return repr(obj)
         else:
             stream = StringIO()
             printer = pretty.RepresentationPrinter(stream, self.verbose,
                 self.max_width, self.newline,
                 max_seq_length=self.max_seq_length,
                 singleton_pprinters=self.singleton_printers,
                 type_pprinters=self.type_printers,
                 deferred_pprinters=self.deferred_printers)
             printer.pretty(obj)
             printer.flush()
             return stream.getvalue()
 
 
 class HTMLFormatter(BaseFormatter):
     """An HTML formatter.
 
     To define the callables that compute the HTML representation of your
     objects, define a :meth:`_repr_html_` method or use the :meth:`for_type`
     or :meth:`for_type_by_name` methods to register functions that handle
     this.
 
     The return value of this formatter should be a valid HTML snippet that
     could be injected into an existing DOM. It should *not* include the
     ```<html>`` or ```<body>`` tags.
     """
     format_type = Unicode('text/html')
 
     print_method = ObjectName('_repr_html_')
 
 
 class MarkdownFormatter(BaseFormatter):
     """A Markdown formatter.
 
     To define the callables that compute the Markdown representation of your
     objects, define a :meth:`_repr_markdown_` method or use the :meth:`for_type`
     or :meth:`for_type_by_name` methods to register functions that handle
     this.
 
     The return value of this formatter should be a valid Markdown.
     """
     format_type = Unicode('text/markdown')
 
     print_method = ObjectName('_repr_markdown_')
 
 class SVGFormatter(BaseFormatter):
     """An SVG formatter.
 
     To define the callables that compute the SVG representation of your
     objects, define a :meth:`_repr_svg_` method or use the :meth:`for_type`
     or :meth:`for_type_by_name` methods to register functions that handle
     this.
 
     The return value of this formatter should be valid SVG enclosed in
     ```<svg>``` tags, that could be injected into an existing DOM. It should
     *not* include the ```<html>`` or ```<body>`` tags.
     """
     format_type = Unicode('image/svg+xml')
 
     print_method = ObjectName('_repr_svg_')
 
 
 class PNGFormatter(BaseFormatter):
     """A PNG formatter.
 
     To define the callables that compute the PNG representation of your
     objects, define a :meth:`_repr_png_` method or use the :meth:`for_type`
     or :meth:`for_type_by_name` methods to register functions that handle
     this.
 
     The return value of this formatter should be raw PNG data, *not*
     base64 encoded.
     """
     format_type = Unicode('image/png')
 
     print_method = ObjectName('_repr_png_')
-    
+
     _return_type = (bytes, str)
 
 
 class JPEGFormatter(BaseFormatter):
     """A JPEG formatter.
 
     To define the callables that compute the JPEG representation of your
     objects, define a :meth:`_repr_jpeg_` method or use the :meth:`for_type`
     or :meth:`for_type_by_name` methods to register functions that handle
     this.
 
     The return value of this formatter should be raw JPEG data, *not*
     base64 encoded.
     """
     format_type = Unicode('image/jpeg')
 
     print_method = ObjectName('_repr_jpeg_')
 
     _return_type = (bytes, str)
 
 
 class LatexFormatter(BaseFormatter):
     """A LaTeX formatter.
 
     To define the callables that compute the LaTeX representation of your
     objects, define a :meth:`_repr_latex_` method or use the :meth:`for_type`
     or :meth:`for_type_by_name` methods to register functions that handle
     this.
 
     The return value of this formatter should be a valid LaTeX equation,
     enclosed in either ```$```, ```$$``` or another LaTeX equation
     environment.
     """
     format_type = Unicode('text/latex')
 
     print_method = ObjectName('_repr_latex_')
 
 
 class JSONFormatter(BaseFormatter):
     """A JSON string formatter.
 
     To define the callables that compute the JSONable representation of
     your objects, define a :meth:`_repr_json_` method or use the :meth:`for_type`
     or :meth:`for_type_by_name` methods to register functions that handle
     this.
 
     The return value of this formatter should be a JSONable list or dict.
     JSON scalars (None, number, string) are not allowed, only dict or list containers.
     """
     format_type = Unicode('application/json')
     _return_type = (list, dict)
 
     print_method = ObjectName('_repr_json_')
-    
+
     def _check_return(self, r, obj):
         """Check that a return value is appropriate
 
         Return the value if so, None otherwise, warning if invalid.
         """
         if r is None:
             return
         md = None
         if isinstance(r, tuple):
             # unpack data, metadata tuple for type checking on first element
             r, md = r
 
         assert not isinstance(
             r, str
         ), "JSON-as-string has been deprecated since IPython < 3"
 
         if md is not None:
             # put the tuple back together
             r = (r, md)
         return super(JSONFormatter, self)._check_return(r, obj)
 
 
 class JavascriptFormatter(BaseFormatter):
     """A Javascript formatter.
 
     To define the callables that compute the Javascript representation of
     your objects, define a :meth:`_repr_javascript_` method or use the
     :meth:`for_type` or :meth:`for_type_by_name` methods to register functions
     that handle this.
 
     The return value of this formatter should be valid Javascript code and
     should *not* be enclosed in ```<script>``` tags.
     """
     format_type = Unicode('application/javascript')
 
     print_method = ObjectName('_repr_javascript_')
 
 
 class PDFFormatter(BaseFormatter):
     """A PDF formatter.
 
     To define the callables that compute the PDF representation of your
     objects, define a :meth:`_repr_pdf_` method or use the :meth:`for_type`
     or :meth:`for_type_by_name` methods to register functions that handle
     this.
 
     The return value of this formatter should be raw PDF data, *not*
     base64 encoded.
     """
     format_type = Unicode('application/pdf')
 
     print_method = ObjectName('_repr_pdf_')
 
     _return_type = (bytes, str)
 
 class IPythonDisplayFormatter(BaseFormatter):
     """An escape-hatch Formatter for objects that know how to display themselves.
-    
+
     To define the callables that compute the representation of your
     objects, define a :meth:`_ipython_display_` method or use the :meth:`for_type`
     or :meth:`for_type_by_name` methods to register functions that handle
     this. Unlike mime-type displays, this method should not return anything,
     instead calling any appropriate display methods itself.
-    
+
     This display formatter has highest priority.
     If it fires, no other display formatter will be called.
 
     Prior to IPython 6.1, `_ipython_display_` was the only way to display custom mime-types
     without registering a new Formatter.
-    
+
     IPython 6.1 introduces `_repr_mimebundle_` for displaying custom mime-types,
     so `_ipython_display_` should only be used for objects that require unusual
     display patterns, such as multiple display calls.
     """
     print_method = ObjectName('_ipython_display_')
     _return_type = (type(None), bool)
 
     @catch_format_error
     def __call__(self, obj):
         """Compute the format for an object."""
         if self.enabled:
             # lookup registered printer
             try:
                 printer = self.lookup(obj)
             except KeyError:
                 pass
             else:
                 printer(obj)
                 return True
             # Finally look for special method names
             method = get_real_method(obj, self.print_method)
             if method is not None:
                 method()
                 return True
 
 
 class MimeBundleFormatter(BaseFormatter):
     """A Formatter for arbitrary mime-types.
 
     Unlike other `_repr_<mimetype>_` methods,
     `_repr_mimebundle_` should return mime-bundle data,
     either the mime-keyed `data` dictionary or the tuple `(data, metadata)`.
     Any mime-type is valid.
 
     To define the callables that compute the mime-bundle representation of your
     objects, define a :meth:`_repr_mimebundle_` method or use the :meth:`for_type`
     or :meth:`for_type_by_name` methods to register functions that handle
     this.
 
     .. versionadded:: 6.1
     """
     print_method = ObjectName('_repr_mimebundle_')
     _return_type = dict
-    
+
     def _check_return(self, r, obj):
         r = super(MimeBundleFormatter, self)._check_return(r, obj)
         # always return (data, metadata):
         if r is None:
             return {}, {}
         if not isinstance(r, tuple):
             return r, {}
         return r
 
     @catch_format_error
     def __call__(self, obj, include=None, exclude=None):
         """Compute the format for an object.
 
         Identical to parent's method but we pass extra parameters to the method.
 
         Unlike other _repr_*_ `_repr_mimebundle_` should allow extra kwargs, in
         particular `include` and `exclude`.
         """
         if self.enabled:
             # lookup registered printer
             try:
                 printer = self.lookup(obj)
             except KeyError:
                 pass
             else:
                 return printer(obj)
             # Finally look for special method names
             method = get_real_method(obj, self.print_method)
 
             if method is not None:
                 return method(include=include, exclude=exclude)
             return None
         else:
             return None
 
 
 FormatterABC.register(BaseFormatter)
 FormatterABC.register(PlainTextFormatter)
 FormatterABC.register(HTMLFormatter)
 FormatterABC.register(MarkdownFormatter)
 FormatterABC.register(SVGFormatter)
 FormatterABC.register(PNGFormatter)
 FormatterABC.register(PDFFormatter)
 FormatterABC.register(JPEGFormatter)
 FormatterABC.register(LatexFormatter)
 FormatterABC.register(JSONFormatter)
 FormatterABC.register(JavascriptFormatter)
 FormatterABC.register(IPythonDisplayFormatter)
 FormatterABC.register(MimeBundleFormatter)
 
 
 def format_display_data(obj, include=None, exclude=None):
     """Return a format data dict for an object.
 
     By default all format types will be computed.
 
     Parameters
     ----------
     obj : object
         The Python object whose format data will be computed.
 
     Returns
     -------
     format_dict : dict
         A dictionary of key/value pairs, one or each format that was
         generated for the object. The keys are the format types, which
         will usually be MIME type strings and the values and JSON'able
         data structure containing the raw data for the representation in
         that format.
     include : list or tuple, optional
         A list of format type strings (MIME types) to include in the
         format data dict. If this is set *only* the format types included
         in this list will be computed.
     exclude : list or tuple, optional
         A list of format type string (MIME types) to exclude in the format
         data dict. If this is set all format types will be computed,
         except for those included in this argument.
     """
     from .interactiveshell import InteractiveShell
 
     return InteractiveShell.instance().display_formatter.format(
         obj,
         include,
         exclude
     )

docs/source/config/integrating.rst

@@ -1,184 +1,186
 .. _integrating:
 
 =====================================
 Integrating your objects with IPython
 =====================================
 
 Tab completion
 ==============
 
 To change the attributes displayed by tab-completing your object, define a
 ``__dir__(self)`` method for it. For more details, see the documentation of the
-built-in `dir() function <http://docs.python.org/library/functions.html#dir>`_.
+built-in :external+python:py:func:`dir`
 
 You can also customise key completions for your objects, e.g. pressing tab after
 ``obj["a``. To do so, define a method ``_ipython_key_completions_()``, which
 returns a list of objects which are possible keys in a subscript expression
 ``obj[key]``.
 
 .. versionadded:: 5.0
    Custom key completions
 
 .. _integrating_rich_display:
 
 Rich display
 ============
 
 Custom methods
-----------------------
+--------------
 
 IPython can display richer representations of objects.
 To do this, you can define ``_ipython_display_()``, or any of a number of
 ``_repr_*_()`` methods.
 Note that these are surrounded by single, not double underscores.
 
 
 .. list-table:: Supported ``_repr_*_`` methods
    :widths: 20 15 15 15
    :header-rows: 1
 
    * - Format
      - REPL
      - Notebook
      - Qt Console
    * - ``_repr_pretty_``
      - yes
      - yes
      - yes
    * - ``_repr_svg_``
      - no
      - yes
      - yes
    * - ``_repr_png_``
      - no
      - yes
      - yes
    * - ``_repr_jpeg_``
      - no
      - yes
      - yes
    * - ``_repr_html_``
      - no
      - yes
      - no
    * - ``_repr_javascript_``
      - no
      - yes
      - no
    * - ``_repr_markdown_``
      - no
      - yes
      - no
    * - ``_repr_latex_``
      - no
      - yes
      - no
    * - ``_repr_mimebundle_``
      - no
      - ?
      - ?
 
 If the methods don't exist, the standard ``repr()`` is used.
 If a method exists and returns ``None``, it is treated the same as if it does not exist.
 In general, *all* available formatters will be called when an object is displayed,
 and it is up to the UI to select which to display.
 A given formatter should not generally change its output based on what other formats are available -
 that should be handled at a different level, such as the :class:`~.DisplayFormatter`, or configuration.
 
 ``_repr_*_`` methods should *return* data of the expected format and have no side effects.
 For example, ``_repr_html_`` should return HTML as a `str` and ``_repr_png_`` should return PNG data as `bytes`.
 
 If you wish to take control of display via your own side effects, use ``_ipython_display_()``.
 
 For example::
 
     class Shout(object):
         def __init__(self, text):
             self.text = text
 
         def _repr_html_(self):
             return "<h1>" + self.text + "</h1>"
 
 
 Special methods
 ^^^^^^^^^^^^^^^
 
 Pretty printing
 """""""""""""""
 
 To customize how your object is pretty-printed, add a ``_repr_pretty_`` method
 to the class.
 The method should accept a pretty printer, and a boolean that indicates whether
 the printer detected a cycle.
 The method should act on the printer to produce your customized pretty output.
 Here is an example::
 
     class MyObject(object):
 
         def _repr_pretty_(self, p, cycle):
             if cycle:
                 p.text('MyObject(...)')
             else:
                 p.text('MyObject[...]')
 
 For details on how to use the pretty printer, see :py:mod:`IPython.lib.pretty`.
 
 More powerful methods
 """""""""""""""""""""
 
 .. class:: MyObject
 
    .. method:: _repr_mimebundle_(include=None, exclude=None)
 
      Should return a dictionary of multiple formats, keyed by mimetype, or a tuple
      of two dictionaries: *data, metadata* (see :ref:`Metadata`).
      If this returns something, other ``_repr_*_`` methods are ignored.
      The method should take keyword arguments ``include`` and ``exclude``, though
      it is not required to respect them.
 
    .. method:: _ipython_display_()
 
       Displays the object as a side effect; the return value is ignored. If this
       is defined, all other display methods are ignored.
 
 
 Metadata
 ^^^^^^^^
 
 We often want to provide frontends with guidance on how to display the data. To
 support this, ``_repr_*_()`` methods (except ``_repr_pretty_``?) can also return a ``(data, metadata)``
 tuple where ``metadata`` is a dictionary containing arbitrary key-value pairs for
 the frontend to interpret. An example use case is ``_repr_jpeg_()``, which can
 be set to return a jpeg image and a ``{'height': 400, 'width': 600}`` dictionary
 to inform the frontend how to size the image.
 
 
 
+.. _third_party_formatting:
+
 Formatters for third-party types
 --------------------------------
 
 The user can also register formatters for types without modifying the class::
 
     from bar.baz import Foo
 
     def foo_html(obj):
         return '<marquee>Foo object %s</marquee>' % obj.name
 
     html_formatter = get_ipython().display_formatter.formatters['text/html']
     html_formatter.for_type(Foo, foo_html)
 
     # Or register a type without importing it - this does the same as above:
     html_formatter.for_type_by_name('bar.baz', 'Foo', foo_html)
 
 Custom exception tracebacks
 ===========================
 
 Rarely, you might want to display a custom traceback when reporting an
 exception. To do this, define the custom traceback using
 `_render_traceback_(self)` method which returns a list of strings, one string
 for each line of the traceback. For example, the `ipyparallel
 <https://ipyparallel.readthedocs.io/>`__ a parallel computing framework for
 IPython, does this to display errors from multiple engines.
 
 Please be conservative in using this feature; by replacing the default traceback
 you may hide important information from the user.