Use an unique object instead of specified flag

IPython/core/magics/history.py

@@ -1,314 +1,311 b''
 """Implementation of magic functions related to History.
 """
 #-----------------------------------------------------------------------------
 #  Copyright (c) 2012, IPython Development Team.
 #
 #  Distributed under the terms of the Modified BSD License.
 #
 #  The full license is in the file COPYING.txt, distributed with this software.
 #-----------------------------------------------------------------------------
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 from __future__ import print_function
 
 # Stdlib
 import os
 from io import open as io_open
 from IPython.external.argparse import Action
 
 # Our own packages
 from IPython.core.error import StdinNotImplementedError
 from IPython.core.magic import Magics, magics_class, line_magic
-from IPython.core.magic_arguments import (argument, defaults, magic_arguments,
+from IPython.core.magic_arguments import (argument, magic_arguments,
                                           parse_argstring)
 from IPython.testing.skipdoctest import skip_doctest
 from IPython.utils import io
 
 #-----------------------------------------------------------------------------
 # Magics class implementation
 #-----------------------------------------------------------------------------
 
 
-class HistoryArgLimitAction(Action):
-    def __call__(self, parser, namespace, values, option_string=None):
-        namespace.limit_specified = True
-        namespace.limit = values
+_unspecified = object()
 
 
 @magics_class
 class HistoryMagics(Magics):
 
     @magic_arguments()
     @argument(
         '-n', dest='print_nums', action='store_true', default=False,
         help="""
         print line numbers for each input.
         This feature is only available if numbered prompts are in use.
         """)
     @argument(
         '-o', dest='get_output', action='store_true', default=False,
         help="also print outputs for each input.")
     @argument(
         '-p', dest='pyprompts', action='store_true', default=False,
         help="""
         print classic '>>>' python prompts before each input.
         This is useful for making documentation, and in conjunction
         with -o, for producing doctest-ready output.
         """)
     @argument(
         '-t', dest='raw', action='store_false', default=True,
         help="""
         print the 'translated' history, as IPython understands it.
         IPython filters your input and converts it all into valid Python
         source before executing it (things like magics or aliases are turned
         into function calls, for example). With this option, you'll see the
         native history instead of the user-entered version: '%%cd /' will be
         seen as 'get_ipython().magic("%%cd /")' instead of '%%cd /'.
         """)
     @argument(
         '-f', dest='filename',
         help="""
         FILENAME: instead of printing the output to the screen, redirect
         it to the given file.  The file is always overwritten, though *when
         it can*, IPython asks for confirmation first. In particular, running
         the command 'history -f FILENAME' from the IPython Notebook
         interface will replace FILENAME even if it already exists *without*
         confirmation.
         """)
     @argument(
         '-g', dest='pattern', nargs='*', default=None,
         help="""
         treat the arg as a glob pattern to search for in (full) history.
         This includes the saved history (almost all commands ever written).
         The pattern may contain '?' to match one unknown character and '*'
         to match any number of unknown characters. Use '%%hist -g' to show
         full saved history (may be very long).
         """)
     @argument(
-        '-l', dest='limit', type=int, nargs='?', action=HistoryArgLimitAction,
+        '-l', dest='limit', type=int, nargs='?', default=_unspecified,
         help="""
         get the last n lines from all sessions. Specify n as a single
         arg, or the default is the last 10 lines.
         """)
     @argument('range', nargs='*')
-    @defaults(limit_specified=False)
     @skip_doctest
     @line_magic
     def history(self, parameter_s = ''):
         """Print input history (_i<n> variables), with most recent last.
 
         By default, input history is printed without line numbers so it can be
         directly pasted into an editor. Use -n to show them.
 
         By default, all input history from the current session is displayed.
         Ranges of history can be indicated using the syntax:
         4      : Line 4, current session
         4-6    : Lines 4-6, current session
         243/1-5: Lines 1-5, session 243
         ~2/7   : Line 7, session 2 before current
         ~8/1-~6/5 : From the first line of 8 sessions ago, to the fifth line
                     of 6 sessions ago.
         Multiple ranges can be entered, separated by spaces
 
         The same syntax is used by %macro, %save, %edit, %rerun
 
         Examples
         --------
         ::
 
           In [6]: %history -n 4-6
           4:a = 12
           5:print a**2
           6:%history -n 4-6
 
         """
 
         if not self.shell.displayhook.do_full_cache:
             print('This feature is only available if numbered prompts '
                   'are in use.')
             return
         args = parse_argstring(self.history, parameter_s)
 
         # For brevity
         history_manager = self.shell.history_manager
 
         def _format_lineno(session, line):
             """Helper function to format line numbers properly."""
             if session in (0, history_manager.session_number):
                 return str(line)
             return "%s/%s" % (session, line)
 
         # Check if output to specific file was requested.
         outfname = args.filename
         if not outfname:
             outfile = io.stdout  # default
             # We don't want to close stdout at the end!
             close_at_end = False
         else:
             if os.path.exists(outfname):
                 try:
                     ans = io.ask_yes_no("File %r exists. Overwrite?" % outfname)
                 except StdinNotImplementedError:
                     ans = True
                 if not ans:
                     print('Aborting.')
                     return
                 print("Overwriting file.")
             outfile = io_open(outfname, 'w', encoding='utf-8')
             close_at_end = True
 
         print_nums = args.print_nums
         get_output = args.get_output
         pyprompts = args.pyprompts
         raw = args.raw
 
         pattern = None
+        limit = None if args.limit is _unspecified else args.limit
 
         if args.pattern is not None:
             if args.pattern:
                 pattern = "*" + " ".join(args.pattern) + "*"
             else:
                 pattern = "*"
             hist = history_manager.search(pattern, raw=raw, output=get_output,
-                                          n=args.limit)
+                                          n=limit)
             print_nums = True
-        elif args.limit_specified:
-            n = 10 if args.limit is None else args.limit
+        elif args.limit is not _unspecified:
+            n = 10 if limit is None else limit
             hist = history_manager.get_tail(n, raw=raw, output=get_output)
         else:
             if args.range:      # Get history by ranges
                 hist = history_manager.get_range_by_str(" ".join(args.range),
                                                         raw, get_output)
             else:               # Just get history for the current session
                 hist = history_manager.get_range(raw=raw, output=get_output)
 
         # We could be displaying the entire history, so let's not try to pull
         # it into a list in memory. Anything that needs more space will just
         # misalign.
         width = 4
 
         for session, lineno, inline in hist:
             # Print user history with tabs expanded to 4 spaces.  The GUI
             # clients use hard tabs for easier usability in auto-indented code,
             # but we want to produce PEP-8 compliant history for safe pasting
             # into an editor.
             if get_output:
                 inline, output = inline
             inline = inline.expandtabs(4).rstrip()
 
             multiline = "\n" in inline
             line_sep = '\n' if multiline else ' '
             if print_nums:
                 print(u'%s:%s' % (_format_lineno(session, lineno).rjust(width),
                         line_sep),  file=outfile, end=u'')
             if pyprompts:
                 print(u">>> ", end=u"", file=outfile)
                 if multiline:
                     inline = "\n... ".join(inline.splitlines()) + "\n..."
             print(inline, file=outfile)
             if get_output and output:
                 print(output, file=outfile)
 
         if close_at_end:
             outfile.close()
 
     @line_magic
     def recall(self, arg):
         r"""Repeat a command, or get command to input line for editing.
 
         %recall and %rep are equivalent.
 
         - %recall (no arguments):
 
         Place a string version of last computation result (stored in the
         special '_' variable) to the next input prompt. Allows you to create
         elaborate command lines without using copy-paste::
 
              In[1]: l = ["hei", "vaan"]
              In[2]: "".join(l)
             Out[2]: heivaan
              In[3]: %recall
              In[4]: heivaan_ <== cursor blinking
 
         %recall 45
 
         Place history line 45 on the next input prompt. Use %hist to find
         out the number.
 
         %recall 1-4
 
         Combine the specified lines into one cell, and place it on the next
         input prompt. See %history for the slice syntax.
 
         %recall foo+bar
 
         If foo+bar can be evaluated in the user namespace, the result is
         placed at the next input prompt. Otherwise, the history is searched
         for lines which contain that substring, and the most recent one is
         placed at the next input prompt.
         """
         if not arg:                 # Last output
             self.shell.set_next_input(str(self.shell.user_ns["_"]))
             return
                                     # Get history range
         histlines = self.shell.history_manager.get_range_by_str(arg)
         cmd = "\n".join(x[2] for x in histlines)
         if cmd:
             self.shell.set_next_input(cmd.rstrip())
             return
 
         try:                        # Variable in user namespace
             cmd = str(eval(arg, self.shell.user_ns))
         except Exception:           # Search for term in history
             histlines = self.shell.history_manager.search("*"+arg+"*")
             for h in reversed([x[2] for x in histlines]):
                 if 'recall' in h or 'rep' in h:
                     continue
                 self.shell.set_next_input(h.rstrip())
                 return
         else:
             self.shell.set_next_input(cmd.rstrip())
         print("Couldn't evaluate or find in history:", arg)
 
     @line_magic
     def rerun(self, parameter_s=''):
         """Re-run previous input
 
         By default, you can specify ranges of input history to be repeated
         (as with %history). With no arguments, it will repeat the last line.
 
         Options:
 
           -l <n> : Repeat the last n lines of input, not including the
           current command.
 
           -g foo : Repeat the most recent line which contains foo
         """
         opts, args = self.parse_options(parameter_s, 'l:g:', mode='string')
         if "l" in opts:         # Last n lines
             n = int(opts['l'])
             hist = self.shell.history_manager.get_tail(n)
         elif "g" in opts:       # Search
             p = "*"+opts['g']+"*"
             hist = list(self.shell.history_manager.search(p))
             for l in reversed(hist):
                 if "rerun" not in l[2]:
                     hist = [l]     # The last match which isn't a %rerun
                     break
             else:
                 hist = []          # No matches except %rerun
         elif args:              # Specify history ranges
             hist = self.shell.history_manager.get_range_by_str(args)
         else:                   # Last line
             hist = self.shell.history_manager.get_tail(1)
         hist = [x[2] for x in hist]
         if not hist:
             print("No lines in history match specification")
             return
         histlines = "\n".join(hist)
         print("=== Executing: ===")
         print(histlines)
         print("=== Output: ===")
         self.shell.run_cell("\n".join(hist), store_history=False)