Add docstring for dict_key_matches

IPython/core/completer.py

@@ -1,1155 +1,1156 b''
 """Word completion for IPython.
 
 This module is a fork of the rlcompleter module in the Python standard
 library.  The original enhancements made to rlcompleter have been sent
 upstream and were accepted as of Python 2.3, but we need a lot more
 functionality specific to IPython, so this module will continue to live as an
 IPython-specific utility.
 
 Original rlcompleter documentation:
 
 This requires the latest extension to the readline module (the
 completes keywords, built-ins and globals in __main__; when completing
 NAME.NAME..., it evaluates (!) the expression up to the last dot and
 completes its attributes.
 
 It's very cool to do "import string" type "string.", hit the
 completion key (twice), and see the list of names defined by the
 string module!
 
 Tip: to use the tab key as the completion key, call
 
     readline.parse_and_bind("tab: complete")
 
 Notes:
 
 - Exceptions raised by the completer function are *ignored* (and
   generally cause the completion to fail).  This is a feature -- since
   readline sets the tty device in raw (or cbreak) mode, printing a
   traceback wouldn't work well without some complicated hoopla to save,
   reset and restore the tty state.
 
 - The evaluation of the NAME.NAME... form may cause arbitrary
   application defined code to be executed if an object with a
   ``__getattr__`` hook is found.  Since it is the responsibility of the
   application (or the user) to enable this feature, I consider this an
   acceptable risk.  More complicated expressions (e.g. function calls or
   indexing operations) are *not* evaluated.
 
 - GNU readline is also used by the built-in functions input() and
   raw_input(), and thus these also benefit/suffer from the completer
   features.  Clearly an interactive application can benefit by
   specifying its own completer function and using raw_input() for all
   its input.
 
 - When the original stdin is not a tty device, GNU readline is never
   used, and this module (and the readline module) are silently inactive.
 """
 
 #*****************************************************************************
 #
 # Since this file is essentially a minimally modified copy of the rlcompleter
 # module which is part of the standard Python distribution, I assume that the
 # proper procedure is to maintain its copyright as belonging to the Python
 # Software Foundation (in addition to my own, for all new code).
 #
 #       Copyright (C) 2008 IPython Development Team
 #       Copyright (C) 2001 Fernando Perez. <[e-mail]>
 #       Copyright (C) 2001 Python Software Foundation, www.python.org
 #
 #  Distributed under the terms of the BSD License.  The full license is in
 #  the file COPYING, distributed as part of this software.
 #
 #*****************************************************************************
 
 #-----------------------------------------------------------------------------
 # Imports
 #-----------------------------------------------------------------------------
 
 import __main__
 import glob
 import inspect
 import itertools
 import keyword
 import os
 import re
 import sys
 
 from IPython.config.configurable import Configurable
 from IPython.core.error import TryNext
 from IPython.core.inputsplitter import ESC_MAGIC
 from IPython.utils import generics
 from IPython.utils import io
 from IPython.utils.decorators import undoc
 from IPython.utils.dir2 import dir2
 from IPython.utils.process import arg_split
 from IPython.utils.py3compat import builtin_mod, string_types
 from IPython.utils.traitlets import CBool, Enum
 
 #-----------------------------------------------------------------------------
 # Globals
 #-----------------------------------------------------------------------------
 
 # Public API
 __all__ = ['Completer','IPCompleter']
 
 if sys.platform == 'win32':
     PROTECTABLES = ' '
 else:
     PROTECTABLES = ' ()[]{}?=\\|;:\'#*"^&'
 
 
 #-----------------------------------------------------------------------------
 # Main functions and classes
 #-----------------------------------------------------------------------------
 
 def has_open_quotes(s):
     """Return whether a string has open quotes.
 
     This simply counts whether the number of quote characters of either type in
     the string is odd.
 
     Returns
     -------
     If there is an open quote, the quote character is returned.  Else, return
     False.
     """
     # We check " first, then ', so complex cases with nested quotes will get
     # the " to take precedence.
     if s.count('"') % 2:
         return '"'
     elif s.count("'") % 2:
         return "'"
     else:
         return False
 
 
 def protect_filename(s):
     """Escape a string to protect certain characters."""
 
     return "".join([(ch in PROTECTABLES and '\\' + ch or ch)
                     for ch in s])
 
 def expand_user(path):
     """Expand '~'-style usernames in strings.
 
     This is similar to :func:`os.path.expanduser`, but it computes and returns
     extra information that will be useful if the input was being used in
     computing completions, and you wish to return the completions with the
     original '~' instead of its expanded value.
 
     Parameters
     ----------
     path : str
       String to be expanded.  If no ~ is present, the output is the same as the
       input.
 
     Returns
     -------
     newpath : str
       Result of ~ expansion in the input path.
     tilde_expand : bool
       Whether any expansion was performed or not.
     tilde_val : str
       The value that ~ was replaced with.
     """
     # Default values
     tilde_expand = False
     tilde_val = ''
     newpath = path
 
     if path.startswith('~'):
         tilde_expand = True
         rest = len(path)-1
         newpath = os.path.expanduser(path)
         if rest:
             tilde_val = newpath[:-rest]
         else:
             tilde_val = newpath
 
     return newpath, tilde_expand, tilde_val
 
 
 def compress_user(path, tilde_expand, tilde_val):
     """Does the opposite of expand_user, with its outputs.
     """
     if tilde_expand:
         return path.replace(tilde_val, '~')
     else:
         return path
 
 
 
 def penalize_magics_key(word):
     """key for sorting that penalizes magic commands in the ordering
 
     Normal words are left alone.
 
     Magic commands have the initial % moved to the end, e.g.
     %matplotlib is transformed as follows:
 
     %matplotlib -> matplotlib%
 
     [The choice of the final % is arbitrary.]
 
     Since "matplotlib" < "matplotlib%" as strings, 
     "timeit" will appear before the magic "%timeit" in the ordering
 
     For consistency, move "%%" to the end, so cell magics appear *after*
     line magics with the same name.
 
     A check is performed that there are no other "%" in the string; 
     if there are, then the string is not a magic command and is left unchanged.
 
     """
 
     # Move any % signs from start to end of the key 
     # provided there are no others elsewhere in the string
 
     if word[:2] == "%%":
         if not "%" in word[2:]:
             return word[2:] + "%%" 
 
     if word[:1] == "%":
         if not "%" in word[1:]:
             return word[1:] + "%"
     
     return word
 
 
 @undoc
 class Bunch(object): pass
 
 
 DELIMS = ' \t\n`!@#$^&*()=+[{]}\\|;:\'",<>?'
 GREEDY_DELIMS = ' =\r\n'
 
 
 class CompletionSplitter(object):
     """An object to split an input line in a manner similar to readline.
 
     By having our own implementation, we can expose readline-like completion in
     a uniform manner to all frontends.  This object only needs to be given the
     line of text to be split and the cursor position on said line, and it
     returns the 'word' to be completed on at the cursor after splitting the
     entire line.
 
     What characters are used as splitting delimiters can be controlled by
     setting the `delims` attribute (this is a property that internally
     automatically builds the necessary regular expression)"""
 
     # Private interface
 
     # A string of delimiter characters.  The default value makes sense for
     # IPython's most typical usage patterns.
     _delims = DELIMS
 
     # The expression (a normal string) to be compiled into a regular expression
     # for actual splitting.  We store it as an attribute mostly for ease of
     # debugging, since this type of code can be so tricky to debug.
     _delim_expr = None
 
     # The regular expression that does the actual splitting
     _delim_re = None
 
     def __init__(self, delims=None):
         delims = CompletionSplitter._delims if delims is None else delims
         self.delims = delims
 
     @property
     def delims(self):
         """Return the string of delimiter characters."""
         return self._delims
 
     @delims.setter
     def delims(self, delims):
         """Set the delimiters for line splitting."""
         expr = '[' + ''.join('\\'+ c for c in delims) + ']'
         self._delim_re = re.compile(expr)
         self._delims = delims
         self._delim_expr = expr
 
     def split_line(self, line, cursor_pos=None):
         """Split a line of text with a cursor at the given position.
         """
         l = line if cursor_pos is None else line[:cursor_pos]
         return self._delim_re.split(l)[-1]
 
 
 class Completer(Configurable):
 
     greedy = CBool(False, config=True,
         help="""Activate greedy completion
 
         This will enable completion on elements of lists, results of function calls, etc.,
         but can be unsafe because the code is actually evaluated on TAB.
         """
     )
     
 
     def __init__(self, namespace=None, global_namespace=None, **kwargs):
         """Create a new completer for the command line.
 
         Completer(namespace=ns,global_namespace=ns2) -> completer instance.
 
         If unspecified, the default namespace where completions are performed
         is __main__ (technically, __main__.__dict__). Namespaces should be
         given as dictionaries.
 
         An optional second namespace can be given.  This allows the completer
         to handle cases where both the local and global scopes need to be
         distinguished.
 
         Completer instances should be used as the completion mechanism of
         readline via the set_completer() call:
 
         readline.set_completer(Completer(my_namespace).complete)
         """
 
         # Don't bind to namespace quite yet, but flag whether the user wants a
         # specific namespace or to use __main__.__dict__. This will allow us
         # to bind to __main__.__dict__ at completion time, not now.
         if namespace is None:
             self.use_main_ns = 1
         else:
             self.use_main_ns = 0
             self.namespace = namespace
 
         # The global namespace, if given, can be bound directly
         if global_namespace is None:
             self.global_namespace = {}
         else:
             self.global_namespace = global_namespace
 
         super(Completer, self).__init__(**kwargs)
 
     def complete(self, text, state):
         """Return the next possible completion for 'text'.
 
         This is called successively with state == 0, 1, 2, ... until it
         returns None.  The completion should begin with 'text'.
 
         """
         if self.use_main_ns:
             self.namespace = __main__.__dict__
 
         if state == 0:
             if "." in text:
                 self.matches = self.attr_matches(text)
             else:
                 self.matches = self.global_matches(text)
         try:
             return self.matches[state]
         except IndexError:
             return None
 
     def global_matches(self, text):
         """Compute matches when text is a simple name.
 
         Return a list of all keywords, built-in functions and names currently
         defined in self.namespace or self.global_namespace that match.
 
         """
         #print 'Completer->global_matches, txt=%r' % text # dbg
         matches = []
         match_append = matches.append
         n = len(text)
         for lst in [keyword.kwlist,
                     builtin_mod.__dict__.keys(),
                     self.namespace.keys(),
                     self.global_namespace.keys()]:
             for word in lst:
                 if word[:n] == text and word != "__builtins__":
                     match_append(word)
         return matches
 
     def attr_matches(self, text):
         """Compute matches when text contains a dot.
 
         Assuming the text is of the form NAME.NAME....[NAME], and is
         evaluatable in self.namespace or self.global_namespace, it will be
         evaluated and its attributes (as revealed by dir()) are used as
         possible completions.  (For class instances, class members are are
         also considered.)
 
         WARNING: this can still invoke arbitrary C code, if an object
         with a __getattr__ hook is evaluated.
 
         """
 
         #io.rprint('Completer->attr_matches, txt=%r' % text) # dbg
         # Another option, seems to work great. Catches things like ''.<tab>
         m = re.match(r"(\S+(\.\w+)*)\.(\w*)$", text)
     
         if m:
             expr, attr = m.group(1, 3)
         elif self.greedy:
             m2 = re.match(r"(.+)\.(\w*)$", self.line_buffer)
             if not m2:
                 return []
             expr, attr = m2.group(1,2)
         else:
             return []
     
         try:
             obj = eval(expr, self.namespace)
         except:
             try:
                 obj = eval(expr, self.global_namespace)
             except:
                 return []
 
         if self.limit_to__all__ and hasattr(obj, '__all__'):
             words = get__all__entries(obj)
         else: 
             words = dir2(obj)
 
         try:
             words = generics.complete_object(obj, words)
         except TryNext:
             pass
         except Exception:
             # Silence errors from completion function
             #raise # dbg
             pass
         # Build match list to return
         n = len(attr)
         res = ["%s.%s" % (expr, w) for w in words if w[:n] == attr ]
         return res
 
 
 def get__all__entries(obj):
     """returns the strings in the __all__ attribute"""
     try:
         words = getattr(obj, '__all__')
     except:
         return []
     
     return [w for w in words if isinstance(w, string_types)]
 
 
 def match_dict_keys(keys, prefix):
     """Used by dict_key_matches, matching the prefix to a list of keys"""
     if not prefix:
         return None, 0, [repr(k) for k in keys
                       if isinstance(k, (string_types, bytes))]
     quote_match = re.search('["\']', prefix)
     quote = quote_match.group()
     try:
         prefix_str = eval(prefix + quote, {})
     except Exception:
         return None, 0, []
     
     token_match = re.search(r'\w*$', prefix, re.UNICODE)
     token_start = token_match.start()
     token_prefix = token_match.group()
 
     # TODO: support bytes in Py3k
     matched = []
     for key in keys:
         try:
             if not key.startswith(prefix_str):
                 continue
         except (AttributeError, TypeError, UnicodeError):
             # Python 3+ TypeError on b'a'.startswith('a') or vice-versa
             continue
 
         # reformat remainder of key to begin with prefix
         rem = key[len(prefix_str):]
         # force repr wrapped in '
         rem_repr = repr(rem + '"')
         if rem_repr.startswith('u') and prefix[0] not in 'uU':
             # Found key is unicode, but prefix is Py2 string.
             # Therefore attempt to interpret key as string.
             try:
                 rem_repr = repr(rem.encode('ascii') + '"')
             except UnicodeEncodeError:
                 continue
 
         rem_repr = rem_repr[1 + rem_repr.index("'"):-2]
         if quote == '"':
             # The entered prefix is quoted with ",
             # but the match is quoted with '.
             # A contained " hence needs escaping for comparison:
             rem_repr = rem_repr.replace('"', '\\"')
 
         # then reinsert prefix from start of token
         matched.append('%s%s' % (token_prefix, rem_repr))
     return quote, token_start, matched
 
 
 def _safe_isinstance(obj, module, class_name):
     """Checks if obj is an instance of module.class_name if loaded
     """
     return (module in sys.modules and
             isinstance(obj, getattr(__import__(module), class_name)))
 
 
 
 class IPCompleter(Completer):
     """Extension of the completer class with IPython-specific features"""
 
     def _greedy_changed(self, name, old, new):
         """update the splitter and readline delims when greedy is changed"""
         if new:
             self.splitter.delims = GREEDY_DELIMS
         else:
             self.splitter.delims = DELIMS
 
         if self.readline:
             self.readline.set_completer_delims(self.splitter.delims)
     
     merge_completions = CBool(True, config=True,
         help="""Whether to merge completion results into a single list
         
         If False, only the completion results from the first non-empty
         completer will be returned.
         """
     )
     omit__names = Enum((0,1,2), default_value=2, config=True,
         help="""Instruct the completer to omit private method names
         
         Specifically, when completing on ``object.<tab>``.
         
         When 2 [default]: all names that start with '_' will be excluded.
         
         When 1: all 'magic' names (``__foo__``) will be excluded.
         
         When 0: nothing will be excluded.
         """
     )
     limit_to__all__ = CBool(default_value=False, config=True,
         help="""Instruct the completer to use __all__ for the completion
         
         Specifically, when completing on ``object.<tab>``.
         
         When True: only those names in obj.__all__ will be included.
         
         When False [default]: the __all__ attribute is ignored 
         """
     )
 
     def __init__(self, shell=None, namespace=None, global_namespace=None,
                  use_readline=True, config=None, **kwargs):
         """IPCompleter() -> completer
 
         Return a completer object suitable for use by the readline library
         via readline.set_completer().
 
         Inputs:
 
         - shell: a pointer to the ipython shell itself.  This is needed
           because this completer knows about magic functions, and those can
           only be accessed via the ipython instance.
 
         - namespace: an optional dict where completions are performed.
 
         - global_namespace: secondary optional dict for completions, to
           handle cases (such as IPython embedded inside functions) where
           both Python scopes are visible.
 
         use_readline : bool, optional
           If true, use the readline library.  This completer can still function
           without readline, though in that case callers must provide some extra
           information on each call about the current line."""
 
         self.magic_escape = ESC_MAGIC
         self.splitter = CompletionSplitter()
 
         # Readline configuration, only used by the rlcompleter method.
         if use_readline:
             # We store the right version of readline so that later code
             import IPython.utils.rlineimpl as readline
             self.readline = readline
         else:
             self.readline = None
 
         # _greedy_changed() depends on splitter and readline being defined:
         Completer.__init__(self, namespace=namespace, global_namespace=global_namespace,
                             config=config, **kwargs)
 
         # List where completion matches will be stored
         self.matches = []
         self.shell = shell
         # Regexp to split filenames with spaces in them
         self.space_name_re = re.compile(r'([^\\] )')
         # Hold a local ref. to glob.glob for speed
         self.glob = glob.glob
 
         # Determine if we are running on 'dumb' terminals, like (X)Emacs
         # buffers, to avoid completion problems.
         term = os.environ.get('TERM','xterm')
         self.dumb_terminal = term in ['dumb','emacs']
 
         # Special handling of backslashes needed in win32 platforms
         if sys.platform == "win32":
             self.clean_glob = self._clean_glob_win32
         else:
             self.clean_glob = self._clean_glob
 
         #regexp to parse docstring for function signature
         self.docstring_sig_re = re.compile(r'^[\w|\s.]+\(([^)]*)\).*')
         self.docstring_kwd_re = re.compile(r'[\s|\[]*(\w+)(?:\s*=\s*.*)')
         #use this if positional argument name is also needed
         #= re.compile(r'[\s|\[]*(\w+)(?:\s*=?\s*.*)')
 
         # All active matcher routines for completion
         self.matchers = [self.python_matches,
                          self.file_matches,
                          self.magic_matches,
                          self.python_func_kw_matches,
                          self.dict_key_matches,
                          ]
 
     def all_completions(self, text):
         """
         Wrapper around the complete method for the benefit of emacs
         and pydb.
         """
         return self.complete(text)[1]
 
     def _clean_glob(self,text):
         return self.glob("%s*" % text)
 
     def _clean_glob_win32(self,text):
         return [f.replace("\\","/")
                 for f in self.glob("%s*" % text)]
 
     def file_matches(self, text):
         """Match filenames, expanding ~USER type strings.
 
         Most of the seemingly convoluted logic in this completer is an
         attempt to handle filenames with spaces in them.  And yet it's not
         quite perfect, because Python's readline doesn't expose all of the
         GNU readline details needed for this to be done correctly.
 
         For a filename with a space in it, the printed completions will be
         only the parts after what's already been typed (instead of the
         full completions, as is normally done).  I don't think with the
         current (as of Python 2.3) Python readline it's possible to do
         better."""
 
         #io.rprint('Completer->file_matches: <%r>' % text) # dbg
 
         # chars that require escaping with backslash - i.e. chars
         # that readline treats incorrectly as delimiters, but we
         # don't want to treat as delimiters in filename matching
         # when escaped with backslash
         if text.startswith('!'):
             text = text[1:]
             text_prefix = '!'
         else:
             text_prefix = ''
 
         text_until_cursor = self.text_until_cursor
         # track strings with open quotes
         open_quotes = has_open_quotes(text_until_cursor)
 
         if '(' in text_until_cursor or '[' in text_until_cursor:
             lsplit = text
         else:
             try:
                 # arg_split ~ shlex.split, but with unicode bugs fixed by us
                 lsplit = arg_split(text_until_cursor)[-1]
             except ValueError:
                 # typically an unmatched ", or backslash without escaped char.
                 if open_quotes:
                     lsplit = text_until_cursor.split(open_quotes)[-1]
                 else:
                     return []
             except IndexError:
                 # tab pressed on empty line
                 lsplit = ""
 
         if not open_quotes and lsplit != protect_filename(lsplit):
             # if protectables are found, do matching on the whole escaped name
             has_protectables = True
             text0,text = text,lsplit
         else:
             has_protectables = False
             text = os.path.expanduser(text)
 
         if text == "":
             return [text_prefix + protect_filename(f) for f in self.glob("*")]
 
         # Compute the matches from the filesystem
         m0 = self.clean_glob(text.replace('\\',''))
 
         if has_protectables:
             # If we had protectables, we need to revert our changes to the
             # beginning of filename so that we don't double-write the part
             # of the filename we have so far
             len_lsplit = len(lsplit)
             matches = [text_prefix + text0 +
                        protect_filename(f[len_lsplit:]) for f in m0]
         else:
             if open_quotes:
                 # if we have a string with an open quote, we don't need to
                 # protect the names at all (and we _shouldn't_, as it
                 # would cause bugs when the filesystem call is made).
                 matches = m0
             else:
                 matches = [text_prefix +
                            protect_filename(f) for f in m0]
 
         #io.rprint('mm', matches)  # dbg
 
         # Mark directories in input list by appending '/' to their names.
         matches = [x+'/' if os.path.isdir(x) else x for x in matches]
         return matches
 
     def magic_matches(self, text):
         """Match magics"""
         #print 'Completer->magic_matches:',text,'lb',self.text_until_cursor # dbg
         # Get all shell magics now rather than statically, so magics loaded at
         # runtime show up too.
         lsm = self.shell.magics_manager.lsmagic()
         line_magics = lsm['line']
         cell_magics = lsm['cell']
         pre = self.magic_escape
         pre2 = pre+pre
         
         # Completion logic:
         # - user gives %%: only do cell magics
         # - user gives %: do both line and cell magics
         # - no prefix: do both
         # In other words, line magics are skipped if the user gives %% explicitly
         bare_text = text.lstrip(pre)
         comp = [ pre2+m for m in cell_magics if m.startswith(bare_text)]
         if not text.startswith(pre2):
             comp += [ pre+m for m in line_magics if m.startswith(bare_text)]
         return comp
 
     def python_matches(self,text):
         """Match attributes or global python names"""
         
         #io.rprint('Completer->python_matches, txt=%r' % text) # dbg
         if "." in text:
             try:
                 matches = self.attr_matches(text)
                 if text.endswith('.') and self.omit__names:
                     if self.omit__names == 1:
                         # true if txt is _not_ a __ name, false otherwise:
                         no__name = (lambda txt:
                                     re.match(r'.*\.__.*?__',txt) is None)
                     else:
                         # true if txt is _not_ a _ name, false otherwise:
                         no__name = (lambda txt:
                                     re.match(r'.*\._.*?',txt) is None)
                     matches = filter(no__name, matches)
             except NameError:
                 # catches <undefined attributes>.<tab>
                 matches = []
         else:
             matches = self.global_matches(text)
 
         return matches
 
     def _default_arguments_from_docstring(self, doc):
         """Parse the first line of docstring for call signature.
 
         Docstring should be of the form 'min(iterable[, key=func])\n'.
         It can also parse cython docstring of the form
         'Minuit.migrad(self, int ncall=10000, resume=True, int nsplit=1)'.
         """
         if doc is None:
             return []
 
         #care only the firstline
         line = doc.lstrip().splitlines()[0]
 
         #p = re.compile(r'^[\w|\s.]+\(([^)]*)\).*')
         #'min(iterable[, key=func])\n' -> 'iterable[, key=func]'
         sig = self.docstring_sig_re.search(line)
         if sig is None:
             return []
         # iterable[, key=func]' -> ['iterable[' ,' key=func]']
         sig = sig.groups()[0].split(',')
         ret = []
         for s in sig:
             #re.compile(r'[\s|\[]*(\w+)(?:\s*=\s*.*)')
             ret += self.docstring_kwd_re.findall(s)
         return ret
 
     def _default_arguments(self, obj):
         """Return the list of default arguments of obj if it is callable,
         or empty list otherwise."""
         call_obj = obj
         ret = []
         if inspect.isbuiltin(obj):
             pass
         elif not (inspect.isfunction(obj) or inspect.ismethod(obj)):
             if inspect.isclass(obj):
                 #for cython embededsignature=True the constructor docstring
                 #belongs to the object itself not __init__
                 ret += self._default_arguments_from_docstring(
                             getattr(obj, '__doc__', ''))
                 # for classes, check for __init__,__new__
                 call_obj = (getattr(obj, '__init__', None) or
                        getattr(obj, '__new__', None))
             # for all others, check if they are __call__able
             elif hasattr(obj, '__call__'):
                 call_obj = obj.__call__
 
         ret += self._default_arguments_from_docstring(
                  getattr(call_obj, '__doc__', ''))
 
         try:
             args,_,_1,defaults = inspect.getargspec(call_obj)
             if defaults:
                 ret+=args[-len(defaults):]
         except TypeError:
             pass
 
         return list(set(ret))
 
     def python_func_kw_matches(self,text):
         """Match named parameters (kwargs) of the last open function"""
         
         if "." in text: # a parameter cannot be dotted
             return []
         try: regexp = self.__funcParamsRegex
         except AttributeError:
             regexp = self.__funcParamsRegex = re.compile(r'''
                 '.*?(?<!\\)' |    # single quoted strings or
                 ".*?(?<!\\)" |    # double quoted strings or
                 \w+          |    # identifier
                 \S                # other characters
                 ''', re.VERBOSE | re.DOTALL)
         # 1. find the nearest identifier that comes before an unclosed
         # parenthesis before the cursor
         # e.g. for "foo (1+bar(x), pa<cursor>,a=1)", the candidate is "foo"
         tokens = regexp.findall(self.text_until_cursor)
         tokens.reverse()
         iterTokens = iter(tokens); openPar = 0
 
         for token in iterTokens:
             if token == ')':
                 openPar -= 1
             elif token == '(':
                 openPar += 1
                 if openPar > 0:
                     # found the last unclosed parenthesis
                     break
         else:
             return []
         # 2. Concatenate dotted names ("foo.bar" for "foo.bar(x, pa" )
         ids = []
         isId = re.compile(r'\w+$').match
 
         while True:
             try:
                 ids.append(next(iterTokens))
                 if not isId(ids[-1]):
                     ids.pop(); break
                 if not next(iterTokens) == '.':
                     break
             except StopIteration:
                 break
         # lookup the candidate callable matches either using global_matches
         # or attr_matches for dotted names
         if len(ids) == 1:
             callableMatches = self.global_matches(ids[0])
         else:
             callableMatches = self.attr_matches('.'.join(ids[::-1]))
         argMatches = []
         for callableMatch in callableMatches:
             try:
                 namedArgs = self._default_arguments(eval(callableMatch,
                                                         self.namespace))
             except:
                 continue
 
             for namedArg in namedArgs:
                 if namedArg.startswith(text):
                     argMatches.append("%s=" %namedArg)
         return argMatches
 
     def dict_key_matches(self, text):
+        "Match string keys in a dictionary, after e.g. 'foo[' "
         def get_keys(obj):
             # Only allow completion for known in-memory dict-like types
             if isinstance(obj, dict) or\
                _safe_isinstance(obj, 'pandas', 'DataFrame'):
                 try:
                     return list(obj.keys())
                 except Exception:
                     return []
             elif _safe_isinstance(obj, 'numpy', 'ndarray'):
                 return obj.dtype.names or []
             return []
 
         try:
             regexps = self.__dict_key_regexps
         except AttributeError:
             dict_key_re_fmt = r'''(?x)
             (  # match dict-referring expression wrt greedy setting
                 %s
             )
             \[   # open bracket
             \s*  # and optional whitespace
             ([uUbB]?  # string prefix (r not handled)
                 (?:   # unclosed string
                     '(?:[^']|(?<!\\)\\')*
                 |
                     "(?:[^"]|(?<!\\)\\")*
                 )
             )?
             $
             '''
             regexps = self.__dict_key_regexps = {
                 False: re.compile(dict_key_re_fmt % '''
                                   # identifiers separated by .
                                   (?!\d)\w+
                                   (?:\.(?!\d)\w+)*
                                   '''),
                 True: re.compile(dict_key_re_fmt % '''
                                  .+
                                  ''')
             }
 
         match = regexps[self.greedy].search(self.text_until_cursor)
         if match is None:
             return []
 
         expr, prefix = match.groups()
         try:
             obj = eval(expr, self.namespace)
         except Exception:
             try:
                 obj = eval(expr, self.global_namespace)
             except Exception:
                 return []
 
         keys = get_keys(obj)
         if not keys:
             return keys
         closing_quote, token_offset, matches = match_dict_keys(keys, prefix)
         if not matches:
             return matches
         
         # get the cursor position of
         # - the text being completed
         # - the start of the key text
         # - the start of the completion
         text_start = len(self.text_until_cursor) - len(text)
         if prefix:
             key_start = match.start(2)
             completion_start = key_start + token_offset
         else:
             key_start = completion_start = match.end()
         
         # grab the leading prefix, to make sure all completions start with `text`
         if text_start > key_start:
             leading = ''
         else:
             leading = text[text_start:completion_start]
         
         # the index of the `[` character
         bracket_idx = match.end(1)
 
         # append closing quote and bracket as appropriate
         # this is *not* appropriate if the opening quote or bracket is outside
         # the text given to this method
         suf = ''
         continuation = self.line_buffer[len(self.text_until_cursor):]
         if key_start > text_start and closing_quote:
             # quotes were opened inside text, maybe close them
             if continuation.startswith(closing_quote):
                 continuation = continuation[len(closing_quote):]
             else:
                 suf += closing_quote
         if bracket_idx > text_start:
             # brackets were opened inside text, maybe close them
             if not continuation.startswith(']'):
                 suf += ']'
         
         return [leading + k + suf for k in matches]
 
     def dispatch_custom_completer(self, text):
         #io.rprint("Custom! '%s' %s" % (text, self.custom_completers)) # dbg
         line = self.line_buffer
         if not line.strip():
             return None
 
         # Create a little structure to pass all the relevant information about
         # the current completion to any custom completer.
         event = Bunch()
         event.line = line
         event.symbol = text
         cmd = line.split(None,1)[0]
         event.command = cmd
         event.text_until_cursor = self.text_until_cursor
 
         #print "\ncustom:{%s]\n" % event # dbg
 
         # for foo etc, try also to find completer for %foo
         if not cmd.startswith(self.magic_escape):
             try_magic = self.custom_completers.s_matches(
                 self.magic_escape + cmd)
         else:
             try_magic = []
 
         for c in itertools.chain(self.custom_completers.s_matches(cmd),
                  try_magic,
                  self.custom_completers.flat_matches(self.text_until_cursor)):
             #print "try",c # dbg
             try:
                 res = c(event)
                 if res:
                     # first, try case sensitive match
                     withcase = [r for r in res if r.startswith(text)]
                     if withcase:
                         return withcase
                     # if none, then case insensitive ones are ok too
                     text_low = text.lower()
                     return [r for r in res if r.lower().startswith(text_low)]
             except TryNext:
                 pass
 
         return None
 
     def complete(self, text=None, line_buffer=None, cursor_pos=None):
         """Find completions for the given text and line context.
 
         Note that both the text and the line_buffer are optional, but at least
         one of them must be given.
 
         Parameters
         ----------
           text : string, optional
             Text to perform the completion on.  If not given, the line buffer
             is split using the instance's CompletionSplitter object.
 
           line_buffer : string, optional
             If not given, the completer attempts to obtain the current line
             buffer via readline.  This keyword allows clients which are
             requesting for text completions in non-readline contexts to inform
             the completer of the entire text.
 
           cursor_pos : int, optional
             Index of the cursor in the full line buffer.  Should be provided by
             remote frontends where kernel has no access to frontend state.
 
         Returns
         -------
         text : str
           Text that was actually used in the completion.
 
         matches : list
           A list of completion matches.
         """
         #io.rprint('\nCOMP1 %r %r %r' % (text, line_buffer, cursor_pos))  # dbg
 
         # if the cursor position isn't given, the only sane assumption we can
         # make is that it's at the end of the line (the common case)
         if cursor_pos is None:
             cursor_pos = len(line_buffer) if text is None else len(text)
 
         # if text is either None or an empty string, rely on the line buffer
         if not text:
             text = self.splitter.split_line(line_buffer, cursor_pos)
 
         # If no line buffer is given, assume the input text is all there was
         if line_buffer is None:
             line_buffer = text
 
         self.line_buffer = line_buffer
         self.text_until_cursor = self.line_buffer[:cursor_pos]
         #io.rprint('COMP2 %r %r %r' % (text, line_buffer, cursor_pos))  # dbg
 
         # Start with a clean slate of completions
         self.matches[:] = []
         custom_res = self.dispatch_custom_completer(text)
         if custom_res is not None:
             # did custom completers produce something?
             self.matches = custom_res
         else:
             # Extend the list of completions with the results of each
             # matcher, so we return results to the user from all
             # namespaces.
             if self.merge_completions:
                 self.matches = []
                 for matcher in self.matchers:
                     try:
                         self.matches.extend(matcher(text))
                     except:
                         # Show the ugly traceback if the matcher causes an
                         # exception, but do NOT crash the kernel!
                         sys.excepthook(*sys.exc_info())
             else:
                 for matcher in self.matchers:
                     self.matches = matcher(text)
                     if self.matches:
                         break
         # FIXME: we should extend our api to return a dict with completions for
         # different types of objects.  The rlcomplete() method could then
         # simply collapse the dict into a list for readline, but we'd have
         # richer completion semantics in other evironments.
 
         # use penalize_magics_key to put magics after variables with same name
         self.matches = sorted(set(self.matches), key=penalize_magics_key)
 
         #io.rprint('COMP TEXT, MATCHES: %r, %r' % (text, self.matches)) # dbg
         return text, self.matches
 
     def rlcomplete(self, text, state):
         """Return the state-th possible completion for 'text'.
 
         This is called successively with state == 0, 1, 2, ... until it
         returns None.  The completion should begin with 'text'.
 
         Parameters
         ----------
           text : string
             Text to perform the completion on.
 
           state : int
             Counter used by readline.
         """
         if state==0:
 
             self.line_buffer = line_buffer = self.readline.get_line_buffer()
             cursor_pos = self.readline.get_endidx()
 
             #io.rprint("\nRLCOMPLETE: %r %r %r" %
             #          (text, line_buffer, cursor_pos) ) # dbg
 
             # if there is only a tab on a line with only whitespace, instead of
             # the mostly useless 'do you want to see all million completions'
             # message, just do the right thing and give the user his tab!
             # Incidentally, this enables pasting of tabbed text from an editor
             # (as long as autoindent is off).
 
             # It should be noted that at least pyreadline still shows file
             # completions - is there a way around it?
 
             # don't apply this on 'dumb' terminals, such as emacs buffers, so
             # we don't interfere with their own tab-completion mechanism.
             if not (self.dumb_terminal or line_buffer.strip()):
                 self.readline.insert_text('\t')
                 sys.stdout.flush()
                 return None
 
             # Note: debugging exceptions that may occur in completion is very
             # tricky, because readline unconditionally silences them.  So if
             # during development you suspect a bug in the completion code, turn
             # this flag on temporarily by uncommenting the second form (don't
             # flip the value in the first line, as the '# dbg' marker can be
             # automatically detected and is used elsewhere).
             DEBUG = False
             #DEBUG = True # dbg
             if DEBUG:
                 try:
                     self.complete(text, line_buffer, cursor_pos)
                 except:
                     import traceback; traceback.print_exc()
             else:
                 # The normal production version is here
 
                 # This method computes the self.matches array
                 self.complete(text, line_buffer, cursor_pos)
 
         try:
             return self.matches[state]
         except IndexError:
             return None