[Docs] Add link on how to register class magics.

I also pushed a change on ipython.github.io that added rel=canonical to
the custommagic page which now point to readthedocs.

That should bias Google into not showing IPython docs version 3 for this
kind of searches.

IPython/core/magic.py

@@ -1,678 +1,680 b''
 # encoding: utf-8
 """Magic functions for InteractiveShell.
 """
 
 #-----------------------------------------------------------------------------
 #  Copyright (C) 2001 Janko Hauser <[e-mail]> and
 #  Copyright (C) 2001 Fernando Perez <[e-mail]>
 #  Copyright (C) 2008 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.
 #-----------------------------------------------------------------------------
 
 import os
 import re
 import sys
 import types
 from getopt import getopt, GetoptError
 
 from traitlets.config.configurable import Configurable
 from IPython.core import oinspect
 from IPython.core.error import UsageError
 from IPython.core.inputsplitter import ESC_MAGIC, ESC_MAGIC2
 from decorator import decorator
 from IPython.utils.ipstruct import Struct
 from IPython.utils.process import arg_split
 from IPython.utils.text import dedent
 from traitlets import Bool, Dict, Instance, observe
 from logging import error
 
 #-----------------------------------------------------------------------------
 # Globals
 #-----------------------------------------------------------------------------
 
 # A dict we'll use for each class that has magics, used as temporary storage to
 # pass information between the @line/cell_magic method decorators and the
 # @magics_class class decorator, because the method decorators have no
 # access to the class when they run.  See for more details:
 # http://stackoverflow.com/questions/2366713/can-a-python-decorator-of-an-instance-method-access-the-class
 
 magics = dict(line={}, cell={})
 
 magic_kinds = ('line', 'cell')
 magic_spec = ('line', 'cell', 'line_cell')
 magic_escapes = dict(line=ESC_MAGIC, cell=ESC_MAGIC2)
 
 #-----------------------------------------------------------------------------
 # Utility classes and functions
 #-----------------------------------------------------------------------------
 
 class Bunch: pass
 
 
 def on_off(tag):
     """Return an ON/OFF string for a 1/0 input. Simple utility function."""
     return ['OFF','ON'][tag]
 
 
 def compress_dhist(dh):
     """Compress a directory history into a new one with at most 20 entries.
 
     Return a new list made from the first and last 10 elements of dhist after
     removal of duplicates.
     """
     head, tail = dh[:-10], dh[-10:]
 
     newhead = []
     done = set()
     for h in head:
         if h in done:
             continue
         newhead.append(h)
         done.add(h)
 
     return newhead + tail
 
 
 def needs_local_scope(func):
     """Decorator to mark magic functions which need to local scope to run."""
     func.needs_local_scope = True
     return func
 
 #-----------------------------------------------------------------------------
 # Class and method decorators for registering magics
 #-----------------------------------------------------------------------------
 
 def magics_class(cls):
     """Class decorator for all subclasses of the main Magics class.
 
     Any class that subclasses Magics *must* also apply this decorator, to
     ensure that all the methods that have been decorated as line/cell magics
     get correctly registered in the class instance.  This is necessary because
     when method decorators run, the class does not exist yet, so they
     temporarily store their information into a module global.  Application of
     this class decorator copies that global data to the class instance and
     clears the global.
 
     Obviously, this mechanism is not thread-safe, which means that the
     *creation* of subclasses of Magic should only be done in a single-thread
     context.  Instantiation of the classes has no restrictions.  Given that
     these classes are typically created at IPython startup time and before user
     application code becomes active, in practice this should not pose any
     problems.
     """
     cls.registered = True
     cls.magics = dict(line = magics['line'],
                       cell = magics['cell'])
     magics['line'] = {}
     magics['cell'] = {}
     return cls
 
 
 def record_magic(dct, magic_kind, magic_name, func):
     """Utility function to store a function as a magic of a specific kind.
 
     Parameters
     ----------
     dct : dict
       A dictionary with 'line' and 'cell' subdicts.
 
     magic_kind : str
       Kind of magic to be stored.
 
     magic_name : str
       Key to store the magic as.
 
     func : function
       Callable object to store.
     """
     if magic_kind == 'line_cell':
         dct['line'][magic_name] = dct['cell'][magic_name] = func
     else:
         dct[magic_kind][magic_name] = func
 
 
 def validate_type(magic_kind):
     """Ensure that the given magic_kind is valid.
 
     Check that the given magic_kind is one of the accepted spec types (stored
     in the global `magic_spec`), raise ValueError otherwise.
     """
     if magic_kind not in magic_spec:
         raise ValueError('magic_kind must be one of %s, %s given' %
                          magic_kinds, magic_kind)
 
 
 # The docstrings for the decorator below will be fairly similar for the two
 # types (method and function), so we generate them here once and reuse the
 # templates below.
 _docstring_template = \
 """Decorate the given {0} as {1} magic.
 
 The decorator can be used with or without arguments, as follows.
 
 i) without arguments: it will create a {1} magic named as the {0} being
 decorated::
 
     @deco
     def foo(...)
 
 will create a {1} magic named `foo`.
 
 ii) with one string argument: which will be used as the actual name of the
 resulting magic::
 
     @deco('bar')
     def foo(...)
 
 will create a {1} magic named `bar`.
+
+To register a class magic use ``Interactiveshell.register_magic(class or instance)``.
 """
 
 # These two are decorator factories.  While they are conceptually very similar,
 # there are enough differences in the details that it's simpler to have them
 # written as completely standalone functions rather than trying to share code
 # and make a single one with convoluted logic.
 
 def _method_magic_marker(magic_kind):
     """Decorator factory for methods in Magics subclasses.
     """
 
     validate_type(magic_kind)
 
     # This is a closure to capture the magic_kind.  We could also use a class,
     # but it's overkill for just that one bit of state.
     def magic_deco(arg):
         call = lambda f, *a, **k: f(*a, **k)
 
         if callable(arg):
             # "Naked" decorator call (just @foo, no args)
             func = arg
             name = func.__name__
             retval = decorator(call, func)
             record_magic(magics, magic_kind, name, name)
         elif isinstance(arg, str):
             # Decorator called with arguments (@foo('bar'))
             name = arg
             def mark(func, *a, **kw):
                 record_magic(magics, magic_kind, name, func.__name__)
                 return decorator(call, func)
             retval = mark
         else:
             raise TypeError("Decorator can only be called with "
                             "string or function")
         return retval
 
     # Ensure the resulting decorator has a usable docstring
     magic_deco.__doc__ = _docstring_template.format('method', magic_kind)
     return magic_deco
 
 
 def _function_magic_marker(magic_kind):
     """Decorator factory for standalone functions.
     """
     validate_type(magic_kind)
     
     # This is a closure to capture the magic_kind.  We could also use a class,
     # but it's overkill for just that one bit of state.
     def magic_deco(arg):
         call = lambda f, *a, **k: f(*a, **k)
 
         # Find get_ipython() in the caller's namespace
         caller = sys._getframe(1)
         for ns in ['f_locals', 'f_globals', 'f_builtins']:
             get_ipython = getattr(caller, ns).get('get_ipython')
             if get_ipython is not None:
                 break
         else:
             raise NameError('Decorator can only run in context where '
                             '`get_ipython` exists')
 
         ip = get_ipython()
 
         if callable(arg):
             # "Naked" decorator call (just @foo, no args)
             func = arg
             name = func.__name__
             ip.register_magic_function(func, magic_kind, name)
             retval = decorator(call, func)
         elif isinstance(arg, str):
             # Decorator called with arguments (@foo('bar'))
             name = arg
             def mark(func, *a, **kw):
                 ip.register_magic_function(func, magic_kind, name)
                 return decorator(call, func)
             retval = mark
         else:
             raise TypeError("Decorator can only be called with "
                              "string or function")
         return retval
 
     # Ensure the resulting decorator has a usable docstring
     ds = _docstring_template.format('function', magic_kind)
 
     ds += dedent("""
     Note: this decorator can only be used in a context where IPython is already
     active, so that the `get_ipython()` call succeeds.  You can therefore use
     it in your startup files loaded after IPython initializes, but *not* in the
     IPython configuration file itself, which is executed before IPython is
     fully up and running.  Any file located in the `startup` subdirectory of
     your configuration profile will be OK in this sense.
     """)
     
     magic_deco.__doc__ = ds
     return magic_deco
 
 
 # Create the actual decorators for public use
 
 # These three are used to decorate methods in class definitions
 line_magic = _method_magic_marker('line')
 cell_magic = _method_magic_marker('cell')
 line_cell_magic = _method_magic_marker('line_cell')
 
 # These three decorate standalone functions and perform the decoration
 # immediately.  They can only run where get_ipython() works
 register_line_magic = _function_magic_marker('line')
 register_cell_magic = _function_magic_marker('cell')
 register_line_cell_magic = _function_magic_marker('line_cell')
 
 #-----------------------------------------------------------------------------
 # Core Magic classes
 #-----------------------------------------------------------------------------
 
 class MagicsManager(Configurable):
     """Object that handles all magic-related functionality for IPython.
     """
     # Non-configurable class attributes
 
     # A two-level dict, first keyed by magic type, then by magic function, and
     # holding the actual callable object as value.  This is the dict used for
     # magic function dispatch
     magics = Dict()
 
     # A registry of the original objects that we've been given holding magics.
     registry = Dict()
 
     shell = Instance('IPython.core.interactiveshell.InteractiveShellABC', allow_none=True)
 
     auto_magic = Bool(True, help=
         "Automatically call line magics without requiring explicit % prefix"
     ).tag(config=True)
     @observe('auto_magic')
     def _auto_magic_changed(self, change):
         self.shell.automagic = change['new']
     
     _auto_status = [
         'Automagic is OFF, % prefix IS needed for line magics.',
         'Automagic is ON, % prefix IS NOT needed for line magics.']
 
     user_magics = Instance('IPython.core.magics.UserMagics', allow_none=True)
 
     def __init__(self, shell=None, config=None, user_magics=None, **traits):
 
         super(MagicsManager, self).__init__(shell=shell, config=config,
                                            user_magics=user_magics, **traits)
         self.magics = dict(line={}, cell={})
         # Let's add the user_magics to the registry for uniformity, so *all*
         # registered magic containers can be found there.
         self.registry[user_magics.__class__.__name__] = user_magics
 
     def auto_status(self):
         """Return descriptive string with automagic status."""
         return self._auto_status[self.auto_magic]
     
     def lsmagic(self):
         """Return a dict of currently available magic functions.
 
         The return dict has the keys 'line' and 'cell', corresponding to the
         two types of magics we support.  Each value is a list of names.
         """
         return self.magics
 
     def lsmagic_docs(self, brief=False, missing=''):
         """Return dict of documentation of magic functions.
 
         The return dict has the keys 'line' and 'cell', corresponding to the
         two types of magics we support. Each value is a dict keyed by magic
         name whose value is the function docstring. If a docstring is
         unavailable, the value of `missing` is used instead.
 
         If brief is True, only the first line of each docstring will be returned.
         """
         docs = {}
         for m_type in self.magics:
             m_docs = {}
             for m_name, m_func in self.magics[m_type].items():
                 if m_func.__doc__:
                     if brief:
                         m_docs[m_name] = m_func.__doc__.split('\n', 1)[0]
                     else:
                         m_docs[m_name] = m_func.__doc__.rstrip()
                 else:
                     m_docs[m_name] = missing
             docs[m_type] = m_docs
         return docs
 
     def register(self, *magic_objects):
         """Register one or more instances of Magics.
 
         Take one or more classes or instances of classes that subclass the main 
         `core.Magic` class, and register them with IPython to use the magic
         functions they provide.  The registration process will then ensure that
         any methods that have decorated to provide line and/or cell magics will
         be recognized with the `%x`/`%%x` syntax as a line/cell magic
         respectively.
 
         If classes are given, they will be instantiated with the default
         constructor.  If your classes need a custom constructor, you should
         instanitate them first and pass the instance.
 
         The provided arguments can be an arbitrary mix of classes and instances.
 
         Parameters
         ----------
         magic_objects : one or more classes or instances
         """
         # Start by validating them to ensure they have all had their magic
         # methods registered at the instance level
         for m in magic_objects:
             if not m.registered:
                 raise ValueError("Class of magics %r was constructed without "
                                  "the @register_magics class decorator")
             if isinstance(m, type):
                 # If we're given an uninstantiated class
                 m = m(shell=self.shell)
 
             # Now that we have an instance, we can register it and update the
             # table of callables
             self.registry[m.__class__.__name__] = m
             for mtype in magic_kinds:
                 self.magics[mtype].update(m.magics[mtype])
 
     def register_function(self, func, magic_kind='line', magic_name=None):
         """Expose a standalone function as magic function for IPython.
 
         This will create an IPython magic (line, cell or both) from a
         standalone function.  The functions should have the following
         signatures: 
 
         * For line magics: `def f(line)`
         * For cell magics: `def f(line, cell)`
         * For a function that does both: `def f(line, cell=None)`
 
         In the latter case, the function will be called with `cell==None` when
         invoked as `%f`, and with cell as a string when invoked as `%%f`.
 
         Parameters
         ----------
         func : callable
           Function to be registered as a magic.
 
         magic_kind : str
           Kind of magic, one of 'line', 'cell' or 'line_cell'
 
         magic_name : optional str
           If given, the name the magic will have in the IPython namespace.  By
           default, the name of the function itself is used.
         """
 
         # Create the new method in the user_magics and register it in the
         # global table
         validate_type(magic_kind)
         magic_name = func.__name__ if magic_name is None else magic_name
         setattr(self.user_magics, magic_name, func)
         record_magic(self.magics, magic_kind, magic_name, func)
 
     def register_alias(self, alias_name, magic_name, magic_kind='line'):
         """Register an alias to a magic function.
 
         The alias is an instance of :class:`MagicAlias`, which holds the
         name and kind of the magic it should call. Binding is done at
         call time, so if the underlying magic function is changed the alias
         will call the new function.
 
         Parameters
         ----------
         alias_name : str
           The name of the magic to be registered.
 
         magic_name : str
           The name of an existing magic.
 
         magic_kind : str
           Kind of magic, one of 'line' or 'cell'
         """
 
         # `validate_type` is too permissive, as it allows 'line_cell'
         # which we do not handle.
         if magic_kind not in magic_kinds:
             raise ValueError('magic_kind must be one of %s, %s given' %
                              magic_kinds, magic_kind)
 
         alias = MagicAlias(self.shell, magic_name, magic_kind)
         setattr(self.user_magics, alias_name, alias)
         record_magic(self.magics, magic_kind, alias_name, alias)
 
 # Key base class that provides the central functionality for magics.
 
 
 class Magics(Configurable):
     """Base class for implementing magic functions.
 
     Shell functions which can be reached as %function_name. All magic
     functions should accept a string, which they can parse for their own
     needs. This can make some functions easier to type, eg `%cd ../`
     vs. `%cd("../")`
 
     Classes providing magic functions need to subclass this class, and they
     MUST:
 
     - Use the method decorators `@line_magic` and `@cell_magic` to decorate
       individual methods as magic functions, AND
 
     - Use the class decorator `@magics_class` to ensure that the magic
       methods are properly registered at the instance level upon instance
       initialization.
 
     See :mod:`magic_functions` for examples of actual implementation classes.
     """
     # Dict holding all command-line options for each magic.
     options_table = None
     # Dict for the mapping of magic names to methods, set by class decorator
     magics = None
     # Flag to check that the class decorator was properly applied
     registered = False
     # Instance of IPython shell
     shell = None
 
     def __init__(self, shell=None, **kwargs):
         if not(self.__class__.registered):
             raise ValueError('Magics subclass without registration - '
                              'did you forget to apply @magics_class?')
         if shell is not None:
             if hasattr(shell, 'configurables'):
                 shell.configurables.append(self)
             if hasattr(shell, 'config'):
                 kwargs.setdefault('parent', shell)
 
         self.shell = shell
         self.options_table = {}
         # The method decorators are run when the instance doesn't exist yet, so
         # they can only record the names of the methods they are supposed to
         # grab.  Only now, that the instance exists, can we create the proper
         # mapping to bound methods.  So we read the info off the original names
         # table and replace each method name by the actual bound method.
         # But we mustn't clobber the *class* mapping, in case of multiple instances.
         class_magics = self.magics
         self.magics = {}
         for mtype in magic_kinds:
             tab = self.magics[mtype] = {}
             cls_tab = class_magics[mtype]
             for magic_name, meth_name in cls_tab.items():
                 if isinstance(meth_name, str):
                     # it's a method name, grab it
                     tab[magic_name] = getattr(self, meth_name)
                 else:
                     # it's the real thing
                     tab[magic_name] = meth_name
         # Configurable **needs** to be initiated at the end or the config
         # magics get screwed up.
         super(Magics, self).__init__(**kwargs)
 
     def arg_err(self,func):
         """Print docstring if incorrect arguments were passed"""
         print('Error in arguments:')
         print(oinspect.getdoc(func))
 
     def format_latex(self, strng):
         """Format a string for latex inclusion."""
 
         # Characters that need to be escaped for latex:
         escape_re = re.compile(r'(%|_|\$|#|&)',re.MULTILINE)
         # Magic command names as headers:
         cmd_name_re = re.compile(r'^(%s.*?):' % ESC_MAGIC,
                                  re.MULTILINE)
         # Magic commands
         cmd_re = re.compile(r'(?P<cmd>%s.+?\b)(?!\}\}:)' % ESC_MAGIC,
                             re.MULTILINE)
         # Paragraph continue
         par_re = re.compile(r'\\$',re.MULTILINE)
 
         # The "\n" symbol
         newline_re = re.compile(r'\\n')
 
         # Now build the string for output:
         #strng = cmd_name_re.sub(r'\n\\texttt{\\textsl{\\large \1}}:',strng)
         strng = cmd_name_re.sub(r'\n\\bigskip\n\\texttt{\\textbf{ \1}}:',
                                 strng)
         strng = cmd_re.sub(r'\\texttt{\g<cmd>}',strng)
         strng = par_re.sub(r'\\\\',strng)
         strng = escape_re.sub(r'\\\1',strng)
         strng = newline_re.sub(r'\\textbackslash{}n',strng)
         return strng
 
     def parse_options(self, arg_str, opt_str, *long_opts, **kw):
         """Parse options passed to an argument string.
 
         The interface is similar to that of :func:`getopt.getopt`, but it
         returns a :class:`~IPython.utils.struct.Struct` with the options as keys
         and the stripped argument string still as a string.
 
         arg_str is quoted as a true sys.argv vector by using shlex.split.
         This allows us to easily expand variables, glob files, quote
         arguments, etc.
 
         Parameters
         ----------
 
         arg_str : str
           The arguments to parse.
 
         opt_str : str
           The options specification.
 
         mode : str, default 'string'
           If given as 'list', the argument string is returned as a list (split
           on whitespace) instead of a string.
 
         list_all : bool, default False
           Put all option values in lists. Normally only options
           appearing more than once are put in a list.
 
         posix : bool, default True
           Whether to split the input line in POSIX mode or not, as per the
           conventions outlined in the :mod:`shlex` module from the standard
           library.
         """
 
         # inject default options at the beginning of the input line
         caller = sys._getframe(1).f_code.co_name
         arg_str = '%s %s' % (self.options_table.get(caller,''),arg_str)
 
         mode = kw.get('mode','string')
         if mode not in ['string','list']:
             raise ValueError('incorrect mode given: %s' % mode)
         # Get options
         list_all = kw.get('list_all',0)
         posix = kw.get('posix', os.name == 'posix')
         strict = kw.get('strict', True)
 
         # Check if we have more than one argument to warrant extra processing:
         odict = {}  # Dictionary with options
         args = arg_str.split()
         if len(args) >= 1:
             # If the list of inputs only has 0 or 1 thing in it, there's no
             # need to look for options
             argv = arg_split(arg_str, posix, strict)
             # Do regular option processing
             try:
                 opts,args = getopt(argv, opt_str, long_opts)
             except GetoptError as e:
                 raise UsageError('%s ( allowed: "%s" %s)' % (e.msg,opt_str,
                                         " ".join(long_opts)))
             for o,a in opts:
                 if o.startswith('--'):
                     o = o[2:]
                 else:
                     o = o[1:]
                 try:
                     odict[o].append(a)
                 except AttributeError:
                     odict[o] = [odict[o],a]
                 except KeyError:
                     if list_all:
                         odict[o] = [a]
                     else:
                         odict[o] = a
 
         # Prepare opts,args for return
         opts = Struct(odict)
         if mode == 'string':
             args = ' '.join(args)
 
         return opts,args
 
     def default_option(self, fn, optstr):
         """Make an entry in the options_table for fn, with value optstr"""
 
         if fn not in self.lsmagic():
             error("%s is not a magic function" % fn)
         self.options_table[fn] = optstr
 
 
 class MagicAlias(object):
     """An alias to another magic function.
 
     An alias is determined by its magic name and magic kind. Lookup
     is done at call time, so if the underlying magic changes the alias
     will call the new function.
 
     Use the :meth:`MagicsManager.register_alias` method or the
     `%alias_magic` magic function to create and register a new alias.
     """
     def __init__(self, shell, magic_name, magic_kind):
         self.shell = shell
         self.magic_name = magic_name
         self.magic_kind = magic_kind
 
         self.pretty_target = '%s%s' % (magic_escapes[self.magic_kind], self.magic_name)
         self.__doc__ = "Alias for `%s`." % self.pretty_target
 
         self._in_call = False
 
     def __call__(self, *args, **kwargs):
         """Call the magic alias."""
         fn = self.shell.find_magic(self.magic_name, self.magic_kind)
         if fn is None:
             raise UsageError("Magic `%s` not found." % self.pretty_target)
 
         # Protect against infinite recursion.
         if self._in_call:
             raise UsageError("Infinite recursion detected; "
                              "magic aliases cannot call themselves.")
         self._in_call = True
         try:
             return fn(*args, **kwargs)
         finally:
             self._in_call = False