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# -*- coding: utf-8 -*-
"""Displayhook for IPython.
This defines a callable class that IPython uses for `sys.displayhook`.
* Fernando Perez
* Brian Granger
* Robert Kern
# Copyright (C) 2008-2010 The IPython Development Team
# Copyright (C) 2001-2007 Fernando Perez <>
# Distributed under the terms of the BSD License. The full license is in
# the file COPYING, distributed as part of this software.
# Imports
import __builtin__
from IPython.config.configurable import Configurable
from IPython.core import prompts
import IPython.utils.generics
from IPython.utils.traitlets import Instance, List
from IPython.utils.warn import warn
# Main displayhook class
# TODO: The DisplayHook class should be split into two classes, one that
# manages the prompts and their synchronization and another that just does the
# displayhook logic and calls into the prompt manager.
# TODO: Move the various attributes (cache_size, colors, input_sep,
# output_sep, output_sep2, ps1, ps2, ps_out, pad_left). Some of these are also
# attributes of InteractiveShell. They should be on ONE object only and the
# other objects should ask that one object for their values.
class DisplayHook(Configurable):
"""The custom IPython displayhook to replace sys.displayhook.
This class does many things, but the basic idea is that it is a callable
that gets called anytime user code returns a value.
Currently this class does more than just the displayhook logic and that
extra logic should eventually be moved out of here.
shell = Instance('IPython.core.interactiveshell.InteractiveShellABC')
def __init__(self, shell=None, cache_size=1000,
colors='NoColor', input_sep='\n',
output_sep='\n', output_sep2='',
ps1 = None, ps2 = None, ps_out = None, pad_left=True,
super(DisplayHook, self).__init__(shell=shell, config=config)
cache_size_min = 3
if cache_size <= 0:
self.do_full_cache = 0
cache_size = 0
elif cache_size < cache_size_min:
self.do_full_cache = 0
cache_size = 0
warn('caching was disabled (min value for cache size is %s).' %
self.do_full_cache = 1
self.cache_size = cache_size
self.input_sep = input_sep
# we need a reference to the user-level namespace = shell
# Set input prompt strings and colors
if cache_size == 0:
if ps1.find('%n') > -1 or ps1.find(r'\#') > -1 \
or ps1.find(r'\N') > -1:
ps1 = '>>> '
if ps2.find('%n') > -1 or ps2.find(r'\#') > -1 \
or ps2.find(r'\N') > -1:
ps2 = '... '
self.ps1_str = self._set_prompt_str(ps1,'In [\\#]: ','>>> ')
self.ps2_str = self._set_prompt_str(ps2,' .\\D.: ','... ')
self.ps_out_str = self._set_prompt_str(ps_out,'Out[\\#]: ','')
self.color_table = prompts.PromptColors
self.prompt1 = prompts.Prompt1(self,sep=input_sep,prompt=self.ps1_str,
self.prompt2 = prompts.Prompt2(self,prompt=self.ps2_str,pad_left=pad_left)
self.prompt_out = prompts.PromptOut(self,sep='',prompt=self.ps_out_str,
# Store the last prompt string each time, we need it for aligning
# continuation and auto-rewrite prompts
self.last_prompt = ''
self.output_sep = output_sep
self.output_sep2 = output_sep2
self._,self.__,self.___ = '','',''
# these are deliberately global:
to_user_ns = {'_':self._,'__':self.__,'___':self.___}
def prompt_count(self):
def _set_prompt_str(self,p_str,cache_def,no_cache_def):
if p_str is None:
if self.do_full_cache:
return cache_def
return no_cache_def
return p_str
def set_colors(self, colors):
"""Set the active color scheme and configure colors for the three
prompt subsystems."""
# FIXME: This modifying of the global prompts.prompt_specials needs
# to be fixed. We need to refactor all of the prompts stuff to use
# proper configuration and traits notifications.
if colors.lower()=='nocolor':
prompts.prompt_specials = prompts.prompt_specials_nocolor
prompts.prompt_specials = prompts.prompt_specials_color
# Methods used in __call__. Override these methods to modify the behavior
# of the displayhook.
def check_for_underscore(self):
"""Check if the user has set the '_' variable by hand."""
# If something injected a '_' variable in __builtin__, delete
# ipython's automatic one so we don't clobber that. gettext() in
# particular uses _, so we need to stay away from it.
if '_' in __builtin__.__dict__:
except KeyError:
def quiet(self):
"""Should we silence the display hook because of ';'?"""
# do not print output if input ends in ';'
cell =[self.prompt_count]
if cell.rstrip().endswith(';'):
return True
except IndexError:
# some uses of ipshellembed may fail here
return False
def start_displayhook(self):
"""Start the displayhook, initializing resources."""
def write_output_prompt(self):
"""Write the output prompt.
The default implementation simply writes the prompt to
# Use write, not print which adds an extra space.
outprompt = str(self.prompt_out)
if self.do_full_cache:
def compute_format_data(self, result):
"""Compute format data of the object to be displayed.
The format data is a generalization of the :func:`repr` of an object.
In the default implementation the format data is a :class:`dict` of
key value pair where the keys are valid MIME types and the values
are JSON'able data structure containing the raw data for that MIME
type. It is up to frontends to determine pick a MIME to to use and
display that data in an appropriate manner.
This method only computes the format data for the object and should
NOT actually print or write that to a stream.
result : object
The Python object passed to the display hook, whose format will be
format_data : dict
A :class:`dict` whose keys are valid MIME types and values are
JSON'able raw data for that MIME type. It is recommended that
all return values of this should always include the "text/plain"
MIME type representation of the object.
def write_format_data(self, format_dict):
"""Write the format data dict to the frontend.
This default version of this method simply writes the plain text
representation of the object to ``io.Term.cout``. Subclasses should
override this method to send the entire `format_dict` to the
format_dict : dict
The format dict for the object passed to `sys.displayhook`.
# We want to print because we want to always make sure we have a
# newline, even if all the prompt separators are ''. This is the
# standard IPython behavior.
result_repr = format_dict['text/plain']
if '\n' in result_repr:
# So that multi-line strings line up with the left column of
# the screen, instead of having the output prompt mess up
# their first line.
# We use the ps_out_str template instead of the expanded prompt
# because the expansion may add ANSI escapes that will interfere
# with our ability to determine whether or not we should add
# a newline.
if self.ps_out_str and not self.ps_out_str.endswith('\n'):
# But avoid extraneous empty lines.
result_repr = '\n' + result_repr
print >>, result_repr
def update_user_ns(self, result):
"""Update user_ns with various things like _, __, _1, etc."""
# Avoid recursive reference when displaying _oh/Out
if result is not['_oh']:
if len(['_oh']) >= self.cache_size and self.do_full_cache:
warn('Output cache limit (currently '+
`self.cache_size`+' entries) hit.\n'
'Flushing cache and resetting history counter...\n'
'The only history variables available will be _,__,___ and _1\n'
'with the current result.')
# Don't overwrite '_' and friends if '_' is in __builtin__ (otherwise
# we cause buggy behavior for things like gettext).
if '_' not in __builtin__.__dict__:
self.___ = self.__
self.__ = self._
self._ = result{'_':self._,
# hackish access to top-level namespace to create _1,_2... dynamically
to_main = {}
if self.do_full_cache:
new_result = '_'+`self.prompt_count`
to_main[new_result] = result['_oh'][self.prompt_count] = result
def log_output(self, format_dict):
"""Log the output."""
if['text/plain'], 'output')[self.prompt_count] = \
def finish_displayhook(self):
"""Finish up all displayhook activities."""
def __call__(self, result=None):
"""Printing with history cache management.
This is invoked everytime the interpreter needs to print, and is
activated by setting the variable sys.displayhook to it.
if result is not None and not self.quiet():
format_dict = self.compute_format_data(result)
def flush(self):
if not self.do_full_cache:
raise ValueError,"You shouldn't have reached the cache flush "\
"if full caching is not enabled!"
# delete auto-generated vars from global namespace
for n in range(1,self.prompt_count + 1):
key = '_'+`n`
except: pass['_oh'].clear()
# Release our own references to objects:
self._, self.__, self.___ = '', '', ''
if '_' not in __builtin__.__dict__:{'_':None,'__':None, '___':None})
import gc
# TODO: Is this really needed?
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