Added clear kwarg to display()

IPython/core/display_functions.py

@@ -1,367 +1,374 b''
 # -*- coding: utf-8 -*-
 """Top-level display functions for displaying object in different formats."""
 
 # Copyright (c) IPython Development Team.
 # Distributed under the terms of the Modified BSD License.
 
 
 from binascii import b2a_hex
 import os
 import sys
 
 __all__ = ['display', 'clear_output', 'publish_display_data', 'update_display', 'DisplayHandle']
 
 #-----------------------------------------------------------------------------
 # utility functions
 #-----------------------------------------------------------------------------
 
 
 def _merge(d1, d2):
     """Like update, but merges sub-dicts instead of clobbering at the top level.
 
     Updates d1 in-place
     """
 
     if not isinstance(d2, dict) or not isinstance(d1, dict):
         return d2
     for key, value in d2.items():
         d1[key] = _merge(d1.get(key), value)
     return d1
 
 
 #-----------------------------------------------------------------------------
 # Main functions
 #-----------------------------------------------------------------------------
 
 
 # use * to indicate transient is keyword-only
 def publish_display_data(data, metadata=None, source=None, *, transient=None, **kwargs):
     """Publish data and metadata to all frontends.
 
     See the ``display_data`` message in the messaging documentation for
     more details about this message type.
 
     Keys of data and metadata can be any mime-type.
 
     Parameters
     ----------
     data : dict
         A dictionary having keys that are valid MIME types (like
         'text/plain' or 'image/svg+xml') and values that are the data for
         that MIME type. The data itself must be a JSON'able data
         structure. Minimally all data should have the 'text/plain' data,
         which can be displayed by all frontends. If more than the plain
         text is given, it is up to the frontend to decide which
         representation to use.
     metadata : dict
         A dictionary for metadata related to the data. This can contain
         arbitrary key, value pairs that frontends can use to interpret
         the data. mime-type keys matching those in data can be used
         to specify metadata about particular representations.
     source : str, deprecated
         Unused.
     transient : dict, keyword-only
         A dictionary of transient data, such as display_id.
         """
     from IPython.core.interactiveshell import InteractiveShell
 
     display_pub = InteractiveShell.instance().display_pub
 
     # only pass transient if supplied,
     # to avoid errors with older ipykernel.
     # TODO: We could check for ipykernel version and provide a detailed upgrade message.
     if transient:
         kwargs['transient'] = transient
 
     display_pub.publish(
         data=data,
         metadata=metadata,
         **kwargs
     )
 
 
 def _new_id():
     """Generate a new random text id with urandom"""
     return b2a_hex(os.urandom(16)).decode('ascii')
 
 
 def display(*objs, include=None, exclude=None, metadata=None, transient=None, display_id=None, **kwargs):
     """Display a Python object in all frontends.
 
     By default all representations will be computed and sent to the frontends.
     Frontends can decide which representation is used and how.
 
     In terminal IPython this will be similar to using :func:`print`, for use in richer
     frontends see Jupyter notebook examples with rich display logic.
 
     Parameters
     ----------
     *objs : object
         The Python objects to display.
     raw : bool, optional
         Are the objects to be displayed already mimetype-keyed dicts of raw display data,
         or Python objects that need to be formatted before display? [default: False]
     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 strings (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.
     metadata : dict, optional
         A dictionary of metadata to associate with the output.
         mime-type keys in this dictionary will be associated with the individual
         representation formats, if they exist.
     transient : dict, optional
         A dictionary of transient data to associate with the output.
         Data in this dict should not be persisted to files (e.g. notebooks).
     display_id : str, bool optional
         Set an id for the display.
         This id can be used for updating this display area later via update_display.
         If given as `True`, generate a new `display_id`
+    clear : bool, optional
+        Should the output area be cleared before displaying anything? If True,
+        this will wait for additional output before clearing. [default: False]
     kwargs: additional keyword-args, optional
         Additional keyword-arguments are passed through to the display publisher.
 
     Returns
     -------
 
     handle: DisplayHandle
         Returns a handle on updatable displays for use with :func:`update_display`,
         if `display_id` is given. Returns :any:`None` if no `display_id` is given
         (default).
 
     Examples
     --------
 
     >>> class Json(object):
     ...     def __init__(self, json):
     ...         self.json = json
     ...     def _repr_pretty_(self, pp, cycle):
     ...         import json
     ...         pp.text(json.dumps(self.json, indent=2))
     ...     def __repr__(self):
     ...         return str(self.json)
     ...
 
     >>> d = Json({1:2, 3: {4:5}})
 
     >>> print(d)
     {1: 2, 3: {4: 5}}
 
     >>> display(d)
     {
       "1": 2,
       "3": {
         "4": 5
       }
     }
 
     >>> def int_formatter(integer, pp, cycle):
     ...     pp.text('I'*integer)
 
     >>> plain = get_ipython().display_formatter.formatters['text/plain']
     >>> plain.for_type(int, int_formatter)
     <function _repr_pprint at 0x...>
     >>> display(7-5)
     II
 
     >>> del plain.type_printers[int]
     >>> display(7-5)
     2
 
     See Also
     --------
 
     :func:`update_display`
 
     Notes
     -----
 
     In Python, objects can declare their textual representation using the
     `__repr__` method. IPython expands on this idea and allows objects to declare
     other, rich representations including:
 
       - HTML
       - JSON
       - PNG
       - JPEG
       - SVG
       - LaTeX
 
     A single object can declare some or all of these representations; all are
     handled by IPython's display system.
 
     The main idea of the first approach is that you have to implement special
     display methods when you define your class, one for each representation you
     want to use. Here is a list of the names of the special methods and the
     values they must return:
 
       - `_repr_html_`: return raw HTML as a string, or a tuple (see below).
       - `_repr_json_`: return a JSONable dict, or a tuple (see below).
       - `_repr_jpeg_`: return raw JPEG data, or a tuple (see below).
       - `_repr_png_`: return raw PNG data, or a tuple (see below).
       - `_repr_svg_`: return raw SVG data as a string, or a tuple (see below).
       - `_repr_latex_`: return LaTeX commands in a string surrounded by "$",
                         or a tuple (see below).
       - `_repr_mimebundle_`: return a full mimebundle containing the mapping
                              from all mimetypes to data.
                              Use this for any mime-type not listed above.
 
     The above functions may also return the object's metadata alonside the
     data.  If the metadata is available, the functions will return a tuple
     containing the data and metadata, in that order.  If there is no metadata
     available, then the functions will return the data only.
 
     When you are directly writing your own classes, you can adapt them for
     display in IPython by following the above approach. But in practice, you
     often need to work with existing classes that you can't easily modify.
 
     You can refer to the documentation on integrating with the display system in
     order to register custom formatters for already existing types
     (:ref:`integrating_rich_display`).
 
     .. versionadded:: 5.4 display available without import
     .. versionadded:: 6.1 display available without import
 
     Since IPython 5.4 and 6.1 :func:`display` is automatically made available to
     the user without import. If you are using display in a document that might
     be used in a pure python context or with older version of IPython, use the
     following import at the top of your file::
 
         from IPython.display import display
 
     """
     from IPython.core.interactiveshell import InteractiveShell
 
     if not InteractiveShell.initialized():
         # Directly print objects.
         print(*objs)
         return
 
-    raw = kwargs.pop('raw', False)
+    raw = kwargs.pop("raw", False)
+    clear = kwargs.pop("clear", False)
     if transient is None:
         transient = {}
     if metadata is None:
         metadata={}
     if display_id:
         if display_id is True:
             display_id = _new_id()
         transient['display_id'] = display_id
     if kwargs.get('update') and 'display_id' not in transient:
         raise TypeError('display_id required for update_display')
     if transient:
         kwargs['transient'] = transient
 
     if not objs and display_id:
         # if given no objects, but still a request for a display_id,
         # we assume the user wants to insert an empty output that
         # can be updated later
         objs = [{}]
         raw = True
 
     if not raw:
         format = InteractiveShell.instance().display_formatter.format
 
+    if clear:
+        clear_output(wait=True)
+
     for obj in objs:
         if raw:
             publish_display_data(data=obj, metadata=metadata, **kwargs)
         else:
             format_dict, md_dict = format(obj, include=include, exclude=exclude)
             if not format_dict:
                 # nothing to display (e.g. _ipython_display_ took over)
                 continue
             if metadata:
                 # kwarg-specified metadata gets precedence
                 _merge(md_dict, metadata)
             publish_display_data(data=format_dict, metadata=md_dict, **kwargs)
     if display_id:
         return DisplayHandle(display_id)
 
 
 # use * for keyword-only display_id arg
 def update_display(obj, *, display_id, **kwargs):
     """Update an existing display by id
 
     Parameters
     ----------
 
     obj:
         The object with which to update the display
     display_id: keyword-only
         The id of the display to update
 
     See Also
     --------
 
     :func:`display`
     """
     kwargs['update'] = True
     display(obj, display_id=display_id, **kwargs)
 
 
 class DisplayHandle(object):
     """A handle on an updatable display
 
     Call `.update(obj)` to display a new object.
 
     Call `.display(obj`) to add a new instance of this display,
     and update existing instances.
 
     See Also
     --------
 
         :func:`display`, :func:`update_display`
 
     """
 
     def __init__(self, display_id=None):
         if display_id is None:
             display_id = _new_id()
         self.display_id = display_id
 
     def __repr__(self):
         return "<%s display_id=%s>" % (self.__class__.__name__, self.display_id)
 
     def display(self, obj, **kwargs):
         """Make a new display with my id, updating existing instances.
 
         Parameters
         ----------
 
         obj:
             object to display
         **kwargs:
             additional keyword arguments passed to display
         """
         display(obj, display_id=self.display_id, **kwargs)
 
     def update(self, obj, **kwargs):
         """Update existing displays with my id
 
         Parameters
         ----------
 
         obj:
             object to display
         **kwargs:
             additional keyword arguments passed to update_display
         """
         update_display(obj, display_id=self.display_id, **kwargs)
 
 
 def clear_output(wait=False):
     """Clear the output of the current cell receiving output.
 
     Parameters
     ----------
     wait : bool [default: false]
         Wait to clear the output until new output is available to replace it."""
     from IPython.core.interactiveshell import InteractiveShell
     if InteractiveShell.initialized():
         InteractiveShell.instance().display_pub.clear_output(wait)
     else:
         print('\033[2K\r', end='')
         sys.stdout.flush()
         print('\033[2K\r', end='')
         sys.stderr.flush()