Merge branch 'paste-errmsg'

IPython/core/hooks.py

@@ -1,235 +1,235 b''
 """hooks for IPython.
 
 In Python, it is possible to overwrite any method of any object if you really
 want to.  But IPython exposes a few 'hooks', methods which are _designed_ to
 be overwritten by users for customization purposes.  This module defines the
 default versions of all such hooks, which get used by IPython if not
 overridden by the user.
 
 hooks are simple functions, but they should be declared with 'self' as their
 first argument, because when activated they are registered into IPython as
 instance methods.  The self argument will be the IPython running instance
 itself, so hooks have full access to the entire IPython object.
 
 If you wish to define a new hook and activate it, you need to put the
 necessary code into a python file which can be either imported or execfile()'d
 from within your profile's ipython_config.py configuration.
 
 For example, suppose that you have a module called 'myiphooks' in your
 PYTHONPATH, which contains the following definition:
 
 import os
 from IPython.core import ipapi
 ip = ipapi.get()
 
 def calljed(self,filename, linenum):
     "My editor hook calls the jed editor directly."
     print "Calling my own editor, jed ..."
     if os.system('jed +%d %s' % (linenum,filename)) != 0:
         raise TryNext()
 
 ip.set_hook('editor', calljed)
 
 You can then enable the functionality by doing 'import myiphooks'
 somewhere in your configuration files or ipython command line.
 """
 
 #*****************************************************************************
 #       Copyright (C) 2005 Fernando Perez. <[e-mail]>
 #
 #  Distributed under the terms of the BSD License.  The full license is in
 #  the file COPYING, distributed as part of this software.
 #*****************************************************************************
 
 import os, bisect
 import sys
 
 from IPython.core.error import TryNext
 
 # List here all the default hooks.  For now it's just the editor functions
 # but over time we'll move here all the public API for user-accessible things.
 
 __all__ = ['editor', 'fix_error_editor', 'synchronize_with_editor',
            'input_prefilter', 'shutdown_hook', 'late_startup_hook',
            'generate_prompt', 'show_in_pager','pre_prompt_hook',
            'pre_run_code_hook', 'clipboard_get']
 
 def editor(self,filename, linenum=None):
     """Open the default editor at the given filename and linenumber.
 
     This is IPython's default editor hook, you can use it as an example to
     write your own modified one.  To set your own editor function as the
     new editor hook, call ip.set_hook('editor',yourfunc)."""
 
     # IPython configures a default editor at startup by reading $EDITOR from
     # the environment, and falling back on vi (unix) or notepad (win32).
     editor = self.editor
 
     # marker for at which line to open the file (for existing objects)
     if linenum is None or editor=='notepad':
         linemark = ''
     else:
         linemark = '+%d' % int(linenum)
 
     # Enclose in quotes if necessary and legal
     if ' ' in editor and os.path.isfile(editor) and editor[0] != '"':
         editor = '"%s"' % editor
 
     # Call the actual editor
     if os.system('%s %s %s' % (editor,linemark,filename)) != 0:
         raise TryNext()
 
 import tempfile
 def fix_error_editor(self,filename,linenum,column,msg):
     """Open the editor at the given filename, linenumber, column and
     show an error message. This is used for correcting syntax errors.
     The current implementation only has special support for the VIM editor,
     and falls back on the 'editor' hook if VIM is not used.
 
     Call ip.set_hook('fix_error_editor',youfunc) to use your own function,
     """
     def vim_quickfix_file():
         t = tempfile.NamedTemporaryFile()
         t.write('%s:%d:%d:%s\n' % (filename,linenum,column,msg))
         t.flush()
         return t
     if os.path.basename(self.editor) != 'vim':
         self.hooks.editor(filename,linenum)
         return
     t = vim_quickfix_file()
     try:
         if os.system('vim --cmd "set errorformat=%f:%l:%c:%m" -q ' + t.name):
             raise TryNext()
     finally:
         t.close()
 
 
 def synchronize_with_editor(self, filename, linenum, column):
         pass
 
 
 class CommandChainDispatcher:
     """ Dispatch calls to a chain of commands until some func can handle it
 
     Usage: instantiate, execute "add" to add commands (with optional
     priority), execute normally via f() calling mechanism.
 
     """
     def __init__(self,commands=None):
         if commands is None:
             self.chain = []
         else:
             self.chain = commands
 
 
     def __call__(self,*args, **kw):
         """ Command chain is called just like normal func.
 
         This will call all funcs in chain with the same args as were given to this
         function, and return the result of first func that didn't raise
         TryNext """
 
         for prio,cmd in self.chain:
             #print "prio",prio,"cmd",cmd #dbg
             try:
                 return cmd(*args, **kw)
             except TryNext, exc:
                 if exc.args or exc.kwargs:
                     args = exc.args
                     kw = exc.kwargs
         # if no function will accept it, raise TryNext up to the caller
-        raise TryNext
+        raise TryNext(*args, **kw)
 
     def __str__(self):
         return str(self.chain)
 
     def add(self, func, priority=0):
         """ Add a func to the cmd chain with given priority """
         bisect.insort(self.chain,(priority,func))
 
     def __iter__(self):
         """ Return all objects in chain.
 
         Handy if the objects are not callable.
         """
         return iter(self.chain)
 
 
 def input_prefilter(self,line):
     """ Default input prefilter
 
     This returns the line as unchanged, so that the interpreter
     knows that nothing was done and proceeds with "classic" prefiltering
     (%magics, !shell commands etc.).
 
     Note that leading whitespace is not passed to this hook. Prefilter
     can't alter indentation.
 
     """
     #print "attempt to rewrite",line #dbg
     return line
 
 
 def shutdown_hook(self):
     """ default shutdown hook
 
     Typically, shotdown hooks should raise TryNext so all shutdown ops are done
     """
 
     #print "default shutdown hook ok" # dbg
     return
 
 
 def late_startup_hook(self):
     """ Executed after ipython has been constructed and configured
 
     """
     #print "default startup hook ok" # dbg
 
 
 def generate_prompt(self, is_continuation):
     """ calculate and return a string with the prompt to display """
     if is_continuation:
         return str(self.displayhook.prompt2)
     return str(self.displayhook.prompt1)
 
 
 def show_in_pager(self,s):
     """ Run a string through pager """
     # raising TryNext here will use the default paging functionality
     raise TryNext
 
 
 def pre_prompt_hook(self):
     """ Run before displaying the next prompt
 
     Use this e.g. to display output from asynchronous operations (in order
     to not mess up text entry)
     """
 
     return None
 
 
 def pre_run_code_hook(self):
     """ Executed before running the (prefiltered) code in IPython """
     return None
 
 
 def clipboard_get(self):
     """ Get text from the clipboard.
     """
     from IPython.lib.clipboard import (
         osx_clipboard_get, tkinter_clipboard_get,
         win32_clipboard_get
     )
     if sys.platform == 'win32':
         chain = [win32_clipboard_get, tkinter_clipboard_get]
     elif sys.platform == 'darwin':
         chain = [osx_clipboard_get, tkinter_clipboard_get]
     else:
         chain = [tkinter_clipboard_get]
     dispatcher = CommandChainDispatcher()
     for func in chain:
         dispatcher.add(func)
     text = dispatcher()
     return text

IPython/frontend/terminal/interactiveshell.py

@@ -1,639 +1,646 b''
 # -*- coding: utf-8 -*-
 """Subclass of InteractiveShell for terminal based frontends."""
 
 #-----------------------------------------------------------------------------
 #  Copyright (C) 2001 Janko Hauser <[e-mail]>
 #  Copyright (C) 2001-2007 Fernando Perez. <[e-mail]>
 #  Copyright (C) 2008-2010  The IPython Development Team
 #
 #  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__
 import bdb
 import os
 import re
 import sys
 
 try:
     from contextlib import nested
 except:
     from IPython.utils.nested_context import nested
 
 from IPython.core.error import TryNext
 from IPython.core.usage import interactive_usage, default_banner
 from IPython.core.interactiveshell import InteractiveShell, InteractiveShellABC
 from IPython.lib.inputhook import enable_gui
 from IPython.lib.pylabtools import pylab_activate
 from IPython.testing.skipdoctest import skip_doctest
 from IPython.utils import py3compat
 from IPython.utils.terminal import toggle_set_term_title, set_term_title
 from IPython.utils.process import abbrev_cwd
-from IPython.utils.warn import warn
+from IPython.utils.warn import warn, error
 from IPython.utils.text import num_ini_spaces
 from IPython.utils.traitlets import Integer, CBool, Unicode
 
 #-----------------------------------------------------------------------------
 # Utilities
 #-----------------------------------------------------------------------------
 
 def get_default_editor():
     try:
         ed = os.environ['EDITOR']
     except KeyError:
         if os.name == 'posix':
             ed = 'vi'  # the only one guaranteed to be there!
         else:
             ed = 'notepad' # same in Windows!
     return ed
 
 #-----------------------------------------------------------------------------
 # Main class
 #-----------------------------------------------------------------------------
 
 class TerminalInteractiveShell(InteractiveShell):
 
     autoedit_syntax = CBool(False, config=True,
         help="auto editing of files with syntax errors.")
     banner = Unicode('')
     banner1 = Unicode(default_banner, config=True,
         help="""The part of the banner to be printed before the profile"""
     )
     banner2 = Unicode('', config=True,
         help="""The part of the banner to be printed after the profile"""
     )
     confirm_exit = CBool(True, config=True,
         help="""
         Set to confirm when you try to exit IPython with an EOF (Control-D
         in Unix, Control-Z/Enter in Windows). By typing 'exit' or 'quit',
         you can force a direct exit without any confirmation.""",
     )
     # This display_banner only controls whether or not self.show_banner()
     # is called when mainloop/interact are called.  The default is False
     # because for the terminal based application, the banner behavior
     # is controlled by Global.display_banner, which IPythonApp looks at
     # to determine if *it* should call show_banner() by hand or not.
     display_banner = CBool(False) # This isn't configurable!
     embedded = CBool(False)
     embedded_active = CBool(False)
     editor = Unicode(get_default_editor(), config=True,
         help="Set the editor used by IPython (default to $EDITOR/vi/notepad)."
     )
     pager = Unicode('less', config=True,
         help="The shell program to be used for paging.")
 
     screen_length = Integer(0, config=True,
         help=
         """Number of lines of your screen, used to control printing of very
         long strings.  Strings longer than this number of lines will be sent
         through a pager instead of directly printed.  The default value for
         this is 0, which means IPython will auto-detect your screen size every
         time it needs to print certain potentially long strings (this doesn't
         change the behavior of the 'print' keyword, it's only triggered
         internally). If for some reason this isn't working well (it needs
         curses support), specify it yourself. Otherwise don't change the
         default.""",
     )
     term_title = CBool(False, config=True,
         help="Enable auto setting the terminal title."
     )
 
     def __init__(self, config=None, ipython_dir=None, profile_dir=None, user_ns=None,
                  user_global_ns=None, custom_exceptions=((),None),
                  usage=None, banner1=None, banner2=None,
                  display_banner=None):
 
         super(TerminalInteractiveShell, self).__init__(
             config=config, profile_dir=profile_dir, user_ns=user_ns,
             user_global_ns=user_global_ns, custom_exceptions=custom_exceptions
         )
         # use os.system instead of utils.process.system by default,
         # because piped system doesn't make sense in the Terminal:
         self.system = self.system_raw
 
         self.init_term_title()
         self.init_usage(usage)
         self.init_banner(banner1, banner2, display_banner)
 
     #-------------------------------------------------------------------------
     # Things related to the terminal
     #-------------------------------------------------------------------------
 
     @property
     def usable_screen_length(self):
         if self.screen_length == 0:
             return 0
         else:
             num_lines_bot = self.separate_in.count('\n')+1
             return self.screen_length - num_lines_bot
 
     def init_term_title(self):
         # Enable or disable the terminal title.
         if self.term_title:
             toggle_set_term_title(True)
             set_term_title('IPython: ' + abbrev_cwd())
         else:
             toggle_set_term_title(False)
 
     #-------------------------------------------------------------------------
     # Things related to aliases
     #-------------------------------------------------------------------------
 
     def init_alias(self):
         # The parent class defines aliases that can be safely used with any
         # frontend.
         super(TerminalInteractiveShell, self).init_alias()
 
         # Now define aliases that only make sense on the terminal, because they
         # need direct access to the console in a way that we can't emulate in
         # GUI or web frontend
         if os.name == 'posix':
             aliases = [('clear', 'clear'), ('more', 'more'), ('less', 'less'),
                        ('man', 'man')]
         elif os.name == 'nt':
             aliases = [('cls', 'cls')]
 
 
         for name, cmd in aliases:
             self.alias_manager.define_alias(name, cmd)
 
     #-------------------------------------------------------------------------
     # Things related to the banner and usage
     #-------------------------------------------------------------------------
 
     def _banner1_changed(self):
         self.compute_banner()
 
     def _banner2_changed(self):
         self.compute_banner()
 
     def _term_title_changed(self, name, new_value):
         self.init_term_title()
 
     def init_banner(self, banner1, banner2, display_banner):
         if banner1 is not None:
             self.banner1 = banner1
         if banner2 is not None:
             self.banner2 = banner2
         if display_banner is not None:
             self.display_banner = display_banner
         self.compute_banner()
 
     def show_banner(self, banner=None):
         if banner is None:
             banner = self.banner
         self.write(banner)
 
     def compute_banner(self):
         self.banner = self.banner1
         if self.profile and self.profile != 'default':
             self.banner += '\nIPython profile: %s\n' % self.profile
         if self.banner2:
             self.banner += '\n' + self.banner2
 
     def init_usage(self, usage=None):
         if usage is None:
             self.usage = interactive_usage
         else:
             self.usage = usage
 
     #-------------------------------------------------------------------------
     # Mainloop and code execution logic
     #-------------------------------------------------------------------------
 
     def mainloop(self, display_banner=None):
         """Start the mainloop.
 
         If an optional banner argument is given, it will override the
         internally created default banner.
         """
 
         with nested(self.builtin_trap, self.display_trap):
 
             while 1:
                 try:
                     self.interact(display_banner=display_banner)
                     #self.interact_with_readline()
                     # XXX for testing of a readline-decoupled repl loop, call
                     # interact_with_readline above
                     break
                 except KeyboardInterrupt:
                     # this should not be necessary, but KeyboardInterrupt
                     # handling seems rather unpredictable...
                     self.write("\nKeyboardInterrupt in interact()\n")
 
     def _replace_rlhist_multiline(self, source_raw, hlen_before_cell):
         """Store multiple lines as a single entry in history"""
 
         # do nothing without readline or disabled multiline
         if not self.has_readline or not self.multiline_history:
             return hlen_before_cell
 
         # windows rl has no remove_history_item
         if not hasattr(self.readline, "remove_history_item"):
             return hlen_before_cell
 
         # skip empty cells
         if not source_raw.rstrip():
             return hlen_before_cell
 
         # nothing changed do nothing, e.g. when rl removes consecutive dups
         hlen = self.readline.get_current_history_length()
         if hlen == hlen_before_cell:
             return hlen_before_cell
 
         for i in range(hlen - hlen_before_cell):
             self.readline.remove_history_item(hlen - i - 1)
         stdin_encoding = sys.stdin.encoding or "utf-8"
         self.readline.add_history(py3compat.unicode_to_str(source_raw.rstrip(),
                                     stdin_encoding))
         return self.readline.get_current_history_length()
 
     def interact(self, display_banner=None):
         """Closely emulate the interactive Python console."""
 
         # batch run -> do not interact
         if self.exit_now:
             return
 
         if display_banner is None:
             display_banner = self.display_banner
 
         if isinstance(display_banner, basestring):
             self.show_banner(display_banner)
         elif display_banner:
             self.show_banner()
 
         more = False
 
         # Mark activity in the builtins
         __builtin__.__dict__['__IPYTHON__active'] += 1
 
         if self.has_readline:
             self.readline_startup_hook(self.pre_readline)
             hlen_b4_cell = self.readline.get_current_history_length()
         else:
             hlen_b4_cell = 0
         # exit_now is set by a call to %Exit or %Quit, through the
         # ask_exit callback.
 
         while not self.exit_now:
             self.hooks.pre_prompt_hook()
             if more:
                 try:
                     prompt = self.hooks.generate_prompt(True)
                 except:
                     self.showtraceback()
                 if self.autoindent:
                     self.rl_do_indent = True
 
             else:
                 try:
                     prompt = self.hooks.generate_prompt(False)
                 except:
                     self.showtraceback()
             try:
                 line = self.raw_input(prompt)
                 if self.exit_now:
                     # quick exit on sys.std[in|out] close
                     break
                 if self.autoindent:
                     self.rl_do_indent = False
 
             except KeyboardInterrupt:
                 #double-guard against keyboardinterrupts during kbdint handling
                 try:
                     self.write('\nKeyboardInterrupt\n')
                     source_raw = self.input_splitter.source_raw_reset()[1]
                     hlen_b4_cell = \
                         self._replace_rlhist_multiline(source_raw, hlen_b4_cell)
                     more = False
                 except KeyboardInterrupt:
                     pass
             except EOFError:
                 if self.autoindent:
                     self.rl_do_indent = False
                     if self.has_readline:
                         self.readline_startup_hook(None)
                 self.write('\n')
                 self.exit()
             except bdb.BdbQuit:
                 warn('The Python debugger has exited with a BdbQuit exception.\n'
                      'Because of how pdb handles the stack, it is impossible\n'
                      'for IPython to properly format this particular exception.\n'
                      'IPython will resume normal operation.')
             except:
                 # exceptions here are VERY RARE, but they can be triggered
                 # asynchronously by signal handlers, for example.
                 self.showtraceback()
             else:
                 self.input_splitter.push(line)
                 more = self.input_splitter.push_accepts_more()
                 if (self.SyntaxTB.last_syntax_error and
                     self.autoedit_syntax):
                     self.edit_syntax_error()
                 if not more:
                     source_raw = self.input_splitter.source_raw_reset()[1]
                     self.run_cell(source_raw, store_history=True)
                     hlen_b4_cell = \
                         self._replace_rlhist_multiline(source_raw, hlen_b4_cell)
 
         # We are off again...
         __builtin__.__dict__['__IPYTHON__active'] -= 1
 
         # Turn off the exit flag, so the mainloop can be restarted if desired
         self.exit_now = False
 
     def raw_input(self, prompt=''):
         """Write a prompt and read a line.
 
         The returned line does not include the trailing newline.
         When the user enters the EOF key sequence, EOFError is raised.
 
         Optional inputs:
 
           - prompt(''): a string to be printed to prompt the user.
 
           - continue_prompt(False): whether this line is the first one or a
           continuation in a sequence of inputs.
         """
         # Code run by the user may have modified the readline completer state.
         # We must ensure that our completer is back in place.
 
         if self.has_readline:
             self.set_readline_completer()
 
         try:
             line = py3compat.str_to_unicode(self.raw_input_original(prompt))
         except ValueError:
             warn("\n********\nYou or a %run:ed script called sys.stdin.close()"
                  " or sys.stdout.close()!\nExiting IPython!")
             self.ask_exit()
             return ""
 
         # Try to be reasonably smart about not re-indenting pasted input more
         # than necessary.  We do this by trimming out the auto-indent initial
         # spaces, if the user's actual input started itself with whitespace.
         if self.autoindent:
             if num_ini_spaces(line) > self.indent_current_nsp:
                 line = line[self.indent_current_nsp:]
                 self.indent_current_nsp = 0
 
         return line
 
     #-------------------------------------------------------------------------
     # Methods to support auto-editing of SyntaxErrors.
     #-------------------------------------------------------------------------
 
     def edit_syntax_error(self):
         """The bottom half of the syntax error handler called in the main loop.
 
         Loop until syntax error is fixed or user cancels.
         """
 
         while self.SyntaxTB.last_syntax_error:
             # copy and clear last_syntax_error
             err = self.SyntaxTB.clear_err_state()
             if not self._should_recompile(err):
                 return
             try:
                 # may set last_syntax_error again if a SyntaxError is raised
                 self.safe_execfile(err.filename,self.user_ns)
             except:
                 self.showtraceback()
             else:
                 try:
                     f = file(err.filename)
                     try:
                         # This should be inside a display_trap block and I
                         # think it is.
                         sys.displayhook(f.read())
                     finally:
                         f.close()
                 except:
                     self.showtraceback()
 
     def _should_recompile(self,e):
         """Utility routine for edit_syntax_error"""
 
         if e.filename in ('<ipython console>','<input>','<string>',
                           '<console>','<BackgroundJob compilation>',
                           None):
 
             return False
         try:
             if (self.autoedit_syntax and
                 not self.ask_yes_no('Return to editor to correct syntax error? '
                               '[Y/n] ','y')):
                 return False
         except EOFError:
             return False
 
         def int0(x):
             try:
                 return int(x)
             except TypeError:
                 return 0
         # always pass integer line and offset values to editor hook
         try:
             self.hooks.fix_error_editor(e.filename,
                 int0(e.lineno),int0(e.offset),e.msg)
         except TryNext:
             warn('Could not open editor')
             return False
         return True
 
     #-------------------------------------------------------------------------
     # Things related to GUI support and pylab
     #-------------------------------------------------------------------------
 
     def enable_pylab(self, gui=None, import_all=True):
         """Activate pylab support at runtime.
 
         This turns on support for matplotlib, preloads into the interactive
         namespace all of numpy and pylab, and configures IPython to correcdtly
         interact with the GUI event loop.  The GUI backend to be used can be
         optionally selected with the optional :param:`gui` argument.
 
         Parameters
         ----------
         gui : optional, string
 
           If given, dictates the choice of matplotlib GUI backend to use
           (should be one of IPython's supported backends, 'tk', 'qt', 'wx' or
           'gtk'), otherwise we use the default chosen by matplotlib (as
           dictated by the matplotlib build-time options plus the user's
           matplotlibrc configuration file).
         """
         # We want to prevent the loading of pylab to pollute the user's
         # namespace as shown by the %who* magics, so we execute the activation
         # code in an empty namespace, and we update *both* user_ns and
         # user_ns_hidden with this information.
         ns = {}
         try:
             gui = pylab_activate(ns, gui, import_all)
         except KeyError:
             error("Backend %r not supported" % gui)
             return
         self.user_ns.update(ns)
         self.user_ns_hidden.update(ns)
         # Now we must activate the gui pylab wants to use, and fix %run to take
         # plot updates into account
         enable_gui(gui)
         self.magic_run = self._pylab_magic_run
 
     #-------------------------------------------------------------------------
     # Things related to exiting
     #-------------------------------------------------------------------------
 
     def ask_exit(self):
         """ Ask the shell to exit. Can be overiden and used as a callback. """
         self.exit_now = True
 
     def exit(self):
         """Handle interactive exit.
 
         This method calls the ask_exit callback."""
         if self.confirm_exit:
             if self.ask_yes_no('Do you really want to exit ([y]/n)?','y'):
                 self.ask_exit()
         else:
             self.ask_exit()
 
     #------------------------------------------------------------------------
     # Magic overrides
     #------------------------------------------------------------------------
     # Once the base class stops inheriting from magic, this code needs to be
     # moved into a separate machinery as well.  For now, at least isolate here
     # the magics which this class needs to implement differently from the base
     # class, or that are unique to it.
 
     def magic_autoindent(self, parameter_s = ''):
         """Toggle autoindent on/off (if available)."""
 
         self.shell.set_autoindent()
         print "Automatic indentation is:",['OFF','ON'][self.shell.autoindent]
 
     @skip_doctest
     def magic_cpaste(self, parameter_s=''):
         """Paste & execute a pre-formatted code block from clipboard.
 
         You must terminate the block with '--' (two minus-signs) or Ctrl-D alone on the
         line. You can also provide your own sentinel with '%paste -s %%' ('%%'
         is the new sentinel for this operation)
 
         The block is dedented prior to execution to enable execution of method
         definitions. '>' and '+' characters at the beginning of a line are
         ignored, to allow pasting directly from e-mails, diff files and
         doctests (the '...' continuation prompt is also stripped).  The
         executed block is also assigned to variable named 'pasted_block' for
         later editing with '%edit pasted_block'.
 
         You can also pass a variable name as an argument, e.g. '%cpaste foo'.
         This assigns the pasted block to variable 'foo' as string, without
         dedenting or executing it (preceding >>> and + is still stripped)
 
         '%cpaste -r' re-executes the block previously entered by cpaste.
 
         Do not be alarmed by garbled output on Windows (it's a readline bug).
         Just press enter and type -- (and press enter again) and the block
         will be what was just pasted.
 
         IPython statements (magics, shell escapes) are not supported (yet).
 
         See also
         --------
         paste: automatically pull code from clipboard.
 
         Examples
         --------
         ::
 
           In [8]: %cpaste
           Pasting code; enter '--' alone on the line to stop.
           :>>> a = ["world!", "Hello"]
           :>>> print " ".join(sorted(a))
           :--
           Hello world!
         """
 
         opts,args = self.parse_options(parameter_s,'rs:',mode='string')
         par = args.strip()
         if opts.has_key('r'):
             self._rerun_pasted()
             return
 
         sentinel = opts.get('s','--')
 
         block = self._strip_pasted_lines_for_code(
             self._get_pasted_lines(sentinel))
 
         self._execute_block(block, par)
 
     def magic_paste(self, parameter_s=''):
         """Paste & execute a pre-formatted code block from clipboard.
 
         The text is pulled directly from the clipboard without user
         intervention and printed back on the screen before execution (unless
         the -q flag is given to force quiet mode).
 
         The block is dedented prior to execution to enable execution of method
         definitions. '>' and '+' characters at the beginning of a line are
         ignored, to allow pasting directly from e-mails, diff files and
         doctests (the '...' continuation prompt is also stripped).  The
         executed block is also assigned to variable named 'pasted_block' for
         later editing with '%edit pasted_block'.
 
         You can also pass a variable name as an argument, e.g. '%paste foo'.
         This assigns the pasted block to variable 'foo' as string, without
         dedenting or executing it (preceding >>> and + is still stripped)
 
         Options
         -------
 
           -r: re-executes the block previously entered by cpaste.
 
           -q: quiet mode: do not echo the pasted text back to the terminal.
 
         IPython statements (magics, shell escapes) are not supported (yet).
 
         See also
         --------
         cpaste: manually paste code into terminal until you mark its end.
         """
         opts,args = self.parse_options(parameter_s,'rq',mode='string')
         par = args.strip()
         if opts.has_key('r'):
             self._rerun_pasted()
             return
-
-        text = self.shell.hooks.clipboard_get()
-        block = self._strip_pasted_lines_for_code(text.splitlines())
+        try:
+            text = self.shell.hooks.clipboard_get()
+            block = self._strip_pasted_lines_for_code(text.splitlines())
+        except TryNext as clipboard_exc:
+            message = getattr(clipboard_exc, 'args')
+            if message:
+                error(message[0])
+            else:
+                error('Could not get text from the clipboard.')
+            return
 
         # By default, echo back to terminal unless quiet mode is requested
         if not opts.has_key('q'):
             write = self.shell.write
             write(self.shell.pycolorize(block))
             if not block.endswith('\n'):
                 write('\n')
             write("## -- End pasted text --\n")
 
         self._execute_block(block, par)
 
     if sys.platform == 'win32':
         def magic_cls(self, s):
             """Clear screen.
             """
             os.system("cls")
 
     def showindentationerror(self):
         super(TerminalInteractiveShell, self).showindentationerror()
         print("If you want to paste code into IPython, try the %paste magic function.")
 
 
 InteractiveShellABC.register(TerminalInteractiveShell)