general cleanup of interactive reference doc

docs/source/interactive/reference.txt

@@ -1,1348 +1,1353 b''
 =================
 IPython reference
 =================
 
 .. warning::
 
     As of the 0.11 version of IPython, some of the features and APIs
     described in this section have been deprecated or are broken.  Our plan
     is to continue to support these features, but they need to be updated
     to take advantage of recent API changes.  Furthermore, this section
     of the documentation need to be updated to reflect all of these changes.
 
 .. _command_line_options:
 
 Command-line usage
 ==================
 
 You start IPython with the command::
 
     $ ipython [options] files
 
 If invoked with no options, it executes all the files listed in sequence
 and drops you into the interpreter while still acknowledging any options
 you may have set in your ipython_config.py. This behavior is different from
 standard Python, which when called as python -i will only execute one
 file and ignore your configuration setup.
 
 Please note that some of the configuration options are not available at
 the command line, simply because they are not practical here. Look into
 your ipythonrc configuration file for details on those. This file is typically 
 installed in the IPYTHON_DIR directory. For Linux
 users, this will be $HOME/.config/ipython, and for other users it will be
 $HOME/.ipython.  For Windows users, $HOME resolves to C:\\Documents and
 Settings\\YourUserName in most instances.
 
 
-
-
-Special Threading Options
--------------------------
+Eventloop integration
+---------------------
 
 Previously IPython had command line options for controlling GUI event loop
 integration (-gthread, -qthread, -q4thread, -wthread, -pylab). As of IPython
 version 0.11, these have been removed. Please see the new ``%gui``
 magic command or :ref:`this section <gui_support>` for details on the new
 interface, or specify the gui at the commandline::
 
     $ ipython gui=qt
 
 
 Regular Options
 ---------------
 
 After the above threading options have been given, regular options can
 follow in any order. All options can be abbreviated to their shortest
 non-ambiguous form and are case-sensitive. One or two dashes can be
 used. Some options have an alternate short form, indicated after a ``|``.
 
 Most options can also be set from your ipythonrc configuration file. See
 the provided example for more details on what the options do. Options
 given at the command line override the values set in the ipythonrc file.
 
 All options with a [no] prepended can be specified in negated form
 (--no-option instead of --option) to turn the feature off.
 
-    -h, --help  print a help message and exit.
+    ``-h, --help``  print a help message and exit.
 
-    --pylab, pylab=<name>
+    ``--pylab, pylab=<name>``
     See :ref:`Matplotlib support <matplotlib_support>`
     for more details.
 
-    autocall=<val>
+    ``autocall=<val>``
 	Make IPython automatically call any callable object even if you
 	didn't type explicit parentheses. For example, 'str 43' becomes
 	'str(43)' automatically. The value can be '0' to disable the feature,
 	'1' for smart autocall, where it is not applied if there are no more
 	arguments on the line, and '2' for full autocall, where all callable
 	objects are automatically called (even if no arguments are
 	present). The default is '1'.
 
-    --[no-]autoindent    
+    ``--[no-]autoindent``
 	Turn automatic indentation on/off.
 
-    --[no-]automagic 
+    ``--[no-]automagic``
 	make magic commands automatic (without needing their first character
 	to be %). Type %magic at the IPython prompt for more information.
 
-    --[no-]autoedit_syntax 
+    ``--[no-]autoedit_syntax``
 	When a syntax error occurs after editing a file, automatically
 	open the file to the trouble causing line for convenient
 	fixing.
 
-    --[no-]banner		Print the initial information banner (default on).
+    ``--[no-]banner``
+	Print the initial information banner (default on).
 
-    c=<command>
+    ``c=<command>``
 	execute the given command string. This is similar to the -c
 	option in the normal Python interpreter.
 
-    cache_size=<n> 
+    ``cache_size=<n>``
 	size of the output cache (maximum number of entries to hold in
 	memory). The default is 1000, you can change it permanently in your
 	config file. Setting it to 0 completely disables the caching system,
 	and the minimum value accepted is 20 (if you provide a value less than
 	20, it is reset to 0 and a warning is issued) This limit is defined
 	because otherwise you'll spend more time re-flushing a too small cache
 	than working.
 
-    --classic
+    ``--classic``
 	Gives IPython a similar feel to the classic Python
 	prompt.
 
-    colors=<scheme> 
+    ``colors=<scheme>``
 	Color scheme for prompts and exception reporting. Currently
 	implemented: NoColor, Linux and LightBG.
 
-    --[no-]color_info 
+    ``--[no-]color_info``
 	IPython can display information about objects via a set of functions,
 	and optionally can use colors for this, syntax highlighting source
 	code and various other elements.  However, because this information is
 	passed through a pager (like 'less') and many pagers get confused with
 	color codes, this option is off by default. You can test it and turn
 	it on permanently in your ipythonrc file if it works for you. As a
 	reference, the 'less' pager supplied with Mandrake 8.2 works ok, but
 	that in RedHat 7.2 doesn't.
 
 	Test it and turn it on permanently if it works with your
 	system. The magic function %color_info allows you to toggle this
 	interactively for testing.
 
-    --[no-]debug 
+    ``--[no-]debug``
 	Show information about the loading process. Very useful to pin down
 	problems with your configuration files or to get details about
 	session restores.
 
-    --[no-]deep_reload: 
+    ``--[no-]deep_reload``
 	IPython can use the deep_reload module which reloads changes in
 	modules recursively (it replaces the reload() function, so you don't
 	need to change anything to use it).  deep_reload() forces a full
 	reload of modules whose code may have changed, which the default
 	reload() function does not.
 
 	When deep_reload is off, IPython will use the normal reload(),
 	but deep_reload will still be available as dreload(). This
 	feature is off by default [which means that you have both
 	normal reload() and dreload()].
 
-    editor=<name>
+    ``editor=<name>``
 	Which editor to use with the %edit command. By default,
 	IPython will honor your EDITOR environment variable (if not
 	set, vi is the Unix default and notepad the Windows one).
 	Since this editor is invoked on the fly by IPython and is
 	meant for editing small code snippets, you may want to use a
 	small, lightweight editor here (in case your default EDITOR is
 	something like Emacs).
 
-    ipython_dir=<name> 
+    ``ipython_dir=<name>``
 	name of your IPython configuration directory IPYTHON_DIR. This
 	can also be specified through the environment variable
 	IPYTHON_DIR.
 
-    -log, l 
-	generate a log file of all input. The file is named
-	ipython_log.py in your current directory (which prevents logs
-	from multiple IPython sessions from trampling each other). You
-	can use this to later restore a session by loading your
-	logfile as a file to be executed with option -logplay (see
-	below).
-
-    logfile=<name>   specify the name of your logfile.
-
-    logplay=<name> 
+    ``logfile=<name>``
+        specify the name of your logfile.
+        
+        This implies ``%logstart`` at the beginning of your session
+        
+        generate a log file of all input. The file is named
+        ipython_log.py in your current directory (which prevents logs
+        from multiple IPython sessions from trampling each other). You
+        can use this to later restore a session by loading your
+        logfile with ``ipython --i ipython_log.py``
+
+    ``logplay=<name>``
+    
+      NOT AVAILABLE in 0.11
 
       you can replay a previous log. For restoring a session as close as
       possible to the state you left it in, use this option (don't just run
       the logfile). With -logplay, IPython will try to reconstruct the
       previous working environment in full, not just execute the commands in
       the logfile.
 
       When a session is restored, logging is automatically turned on
       again with the name of the logfile it was invoked with (it is
       read from the log header). So once you've turned logging on for
       a session, you can quit IPython and reload it as many times as
       you want and it will continue to log its history and restore
       from the beginning every time.
       
       Caveats: there are limitations in this option. The history
       variables _i*,_* and _dh don't get restored properly. In the
       future we will try to implement full session saving by writing
       and retrieving a 'snapshot' of the memory state of IPython. But
       our first attempts failed because of inherent limitations of
       Python's Pickle module, so this may have to wait.
 
-    --[no-]messages   
+    ``--[no-]messages``
 	Print messages which IPython collects about its startup
 	process (default on).
 
-    --[no-]pdb
+    ``--[no-]pdb``
 	Automatically call the pdb debugger after every uncaught
 	exception. If you are used to debugging using pdb, this puts
 	you automatically inside of it after any call (either in
 	IPython or in code called by it) which triggers an exception
 	which goes uncaught.
 
-    --[no-]pprint
+    ``--[no-]pprint``
 	ipython can optionally use the pprint (pretty printer) module
 	for displaying results. pprint tends to give a nicer display
 	of nested data structures. If you like it, you can turn it on
 	permanently in your config file (default off).
 
-    profile=<name>
+    ``profile=<name>``
 
-    Select the IPython profile by name.  
+	Select the IPython profile by name.
     
-    This is a quick way to keep and load multiple
+	This is a quick way to keep and load multiple
 	config files for different tasks, especially if you use the
 	include option of config files. You can keep a basic
-	IPYTHON_DIR/ipythonrc file and then have other 'profiles' which
+	:file:`IPYTHON_DIR/profile_default/ipython_config.py` file 
+	and then have other 'profiles' which
 	include this one and load extra things for particular
 	tasks. For example:
 
 	1. $IPYTHON_DIR/profile_default : load basic things you always want.
 	2. $IPYTHON_DIR/profile_math : load (1) and basic math-related modules.
 	3. $IPYTHON_DIR/profile_numeric : load (1) and Numeric and plotting modules.
 
 	Since it is possible to create an endless loop by having
 	circular file inclusions, IPython will stop if it reaches 15
 	recursive inclusions.
 
-    InteractiveShell.prompt_in1=<string>
+    ``InteractiveShell.prompt_in1=<string>``
 
-        Specify the string used for input prompts. Note that if you are using
+	Specify the string used for input prompts. Note that if you are using
 	numbered prompts, the number is represented with a '\#' in the
 	string. Don't forget to quote strings with spaces embedded in
 	them. Default: 'In [\#]:'.  The :ref:`prompts section <prompts>`
 	discusses in detail all the available escapes to customize your
 	prompts.
 
-    InteractiveShell.prompt_in2=<string>
+    ``InteractiveShell.prompt_in2=<string>``
 	Similar to the previous option, but used for the continuation
 	prompts. The special sequence '\D' is similar to '\#', but
 	with all digits replaced dots (so you can have your
 	continuation prompt aligned with your input prompt).  Default:
 	' .\D.:' (note three spaces at the start for alignment with
 	'In [\#]').
 
-    InteractiveShell.prompt_out=<string> 
+    ``InteractiveShell.prompt_out=<string>``
 	String used for output prompts, also uses numbers like
 	prompt_in1. Default: 'Out[\#]:'
 
-    --quick
-    start in bare bones mode (no config file loaded).
+    ``--quick``
+        start in bare bones mode (no config file loaded).
 
-    config_file=<name>   
+    ``config_file=<name>``
 	name of your IPython resource configuration file. Normally
 	IPython loads ipython_config.py (from current directory) or
 	IPYTHON_DIR/profile_default.
 
 	If the loading of your config file fails, IPython starts with
 	a bare bones configuration (no modules loaded at all).
 
-    --[no-]readline
+    ``--[no-]readline``
 	use the readline library, which is needed to support name
 	completion and command history, among other things.  It is
 	enabled by default, but may cause problems for users of
 	X/Emacs in Python comint or shell buffers.
 
 	Note that X/Emacs 'eterm' buffers (opened with M-x term) support
 	IPython's readline and syntax coloring fine, only 'emacs' (M-x
 	shell and C-c !) buffers do not.
 
-    TerminalInteractiveShell.screen_length=<n>
+    ``TerminalInteractiveShell.screen_length=<n>``
 	number of lines of your screen. This is 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.
 
-    TerminalInteractiveShell.separate_in=<string>
+    ``TerminalInteractiveShell.separate_in=<string>``
 
 	separator before input prompts.
 	Default: '\n'
 
-    TerminalInteractiveShell.separate_out=<string>  
+    ``TerminalInteractiveShell.separate_out=<string>``
         separator before output prompts.
         Default: nothing.
 
-    TerminalInteractiveShell.separate_out2=<string>
+    ``TerminalInteractiveShell.separate_out2=<string>``
 	separator after output prompts.
 	Default: nothing.
 	For these three options, use the value 0 to specify no separator.
 
-    --nosep
+    ``--nosep``
 	shorthand for setting the above separators to empty strings.
 	
 	Simply removes all input/output separators.
 
-    --init
+    ``--init``
 	allows you to initialize a profile dir for configuration when you
 	install a new version of IPython or want to use a new profile.
 	Since new versions may include new command line options or example
 	files, this copies updated config files. Note that you should probably
 	use %upgrade instead,it's a safer alternative.
 
-    --version    print version information and exit.
+    ``--version``    print version information and exit.
 
-    xmode=<modename>
+    ``xmode=<modename>``
 
 	Mode for exception reporting.
 
 	Valid modes: Plain, Context and Verbose.
 
 	* Plain: similar to python's normal traceback printing.
 	* Context: prints 5 lines of context source code around each
 	  line in the traceback.
 	* Verbose: similar to Context, but additionally prints the
 	  variables currently visible where the exception happened
 	  (shortening their strings if too long). This can potentially be
 	  very slow, if you happen to have a huge data structure whose
 	  string representation is complex to compute. Your computer may
 	  appear to freeze for a while with cpu usage at 100%. If this
 	  occurs, you can cancel the traceback with Ctrl-C (maybe hitting it
 	  more than once).
 
 Interactive use
 ===============
 
 IPython is meant to work as a drop-in
 replacement for the standard interactive interpreter. As such, any code
 which is valid python should execute normally under IPython (cases where
 this is not true should be reported as bugs). It does, however, offer
 many features which are not available at a standard python prompt. What
 follows is a list of these.
 
 
 Caution for Windows users
 -------------------------
 
 Windows, unfortunately, uses the '\\' character as a path
 separator. This is a terrible choice, because '\\' also represents the
 escape character in most modern programming languages, including
 Python. For this reason, using '/' character is recommended if you
 have problems with ``\``.  However, in Windows commands '/' flags
 options, so you can not use it for the root directory. This means that
 paths beginning at the root must be typed in a contrived manner like:
 ``%copy \opt/foo/bar.txt \tmp``
 
 .. _magic:
 
 Magic command system
 --------------------
 
 IPython will treat any line whose first character is a % as a special
 call to a 'magic' function. These allow you to control the behavior of
 IPython itself, plus a lot of system-type features. They are all
 prefixed with a % character, but parameters are given without
 parentheses or quotes.
 
 Example: typing ``%cd mydir`` changes your working directory to 'mydir', if it
 exists.
 
 If you have 'automagic' enabled (as it by default), you don't need
 to type in the % explicitly. IPython will scan its internal list of
 magic functions and call one if it exists. With automagic on you can
 then just type ``cd mydir`` to go to directory 'mydir'. The automagic
 system has the lowest possible precedence in name searches, so defining
 an identifier with the same name as an existing magic function will
 shadow it for automagic use. You can still access the shadowed magic
 function by explicitly using the % character at the beginning of the line.
 
 An example (with automagic on) should clarify all this:
 
 .. sourcecode:: ipython
 
     In [1]: cd ipython # %cd is called by automagic
 
     /home/fperez/ipython
 
     In [2]: cd=1 # now cd is just a variable
 
     In [3]: cd .. # and doesn't work as a function anymore
 
     ------------------------------
 
         File "<console>", line 1
 
           cd ..
 
               ^
 
     SyntaxError: invalid syntax
 
     In [4]: %cd .. # but %cd always works
 
     /home/fperez
 
     In [5]: del cd # if you remove the cd variable
 
     In [6]: cd ipython # automagic can work again
 
     /home/fperez/ipython
 
 You can define your own magic functions to extend the system. The
 following example defines a new magic command, %impall:
 
 .. sourcecode:: python
 
     ip = get_ipython()
 
     def doimp(self, arg):
 
         ip = self.api
 
         ip.ex("import %s; reload(%s); from %s import *" % (
 
         arg,arg,arg)
 
         )
 
     ip.expose_magic('impall', doimp)
 
 Type %magic for more information, including a list of all available
 magic functions at any time and their docstrings. You can also type
 %magic_function_name? (see sec. 6.4 <#sec:dyn-object-info> for
 information on the '?' system) to get information about any particular
 magic function you are interested in.
 
 The API documentation for the :mod:`IPython.core.magic` module contains the full
 docstrings of all currently available magic commands.
 
 
 Access to the standard Python help
 ----------------------------------
 
 As of Python 2.1, a help system is available with access to object docstrings
 and the Python manuals. Simply type 'help' (no quotes) to access it. You can
 also type help(object) to obtain information about a given object, and
 help('keyword') for information on a keyword. As noted :ref:`here
 <accessing_help>`, you need to properly configure your environment variable
 PYTHONDOCS for this feature to work correctly.
 
 .. _dynamic_object_info:
 
 Dynamic object information
 --------------------------
 
 Typing ?word or word? prints detailed information about an object. If
 certain strings in the object are too long (docstrings, code, etc.) they
 get snipped in the center for brevity. This system gives access variable
 types and values, full source code for any object (if available),
 function prototypes and other useful information.
 
 Typing ??word or word?? gives access to the full information without
 snipping long strings. Long strings are sent to the screen through the
 less pager if longer than the screen and printed otherwise. On systems
 lacking the less command, IPython uses a very basic internal pager.
 
 The following magic functions are particularly useful for gathering
 information about your working environment. You can get more details by
 typing %magic or querying them individually (use %function_name? with or
 without the %), this is just a summary:
 
     * **%pdoc <object>**: Print (or run through a pager if too long) the
       docstring for an object. If the given object is a class, it will
       print both the class and the constructor docstrings.
     * **%pdef <object>**: Print the definition header for any callable
       object. If the object is a class, print the constructor information.
     * **%psource <object>**: Print (or run through a pager if too long)
       the source code for an object.
     * **%pfile <object>**: Show the entire source file where an object was
       defined via a pager, opening it at the line where the object
       definition begins.
     * **%who/%whos**: These functions give information about identifiers
       you have defined interactively (not things you loaded or defined
       in your configuration files). %who just prints a list of
       identifiers and %whos prints a table with some basic details about
       each identifier.
 
 Note that the dynamic object information functions (?/??, %pdoc, %pfile,
 %pdef, %psource) give you access to documentation even on things which
 are not really defined as separate identifiers. Try for example typing
 {}.get? or after doing import os, type os.path.abspath??.
 
 
 .. _readline:
 
 Readline-based features
 -----------------------
 
 These features require the GNU readline library, so they won't work if
 your Python installation lacks readline support. We will first describe
 the default behavior IPython uses, and then how to change it to suit
 your preferences.
 
 
 Command line completion
 +++++++++++++++++++++++
 
 At any time, hitting TAB will complete any available python commands or
 variable names, and show you a list of the possible completions if
 there's no unambiguous one. It will also complete filenames in the
 current directory if no python names match what you've typed so far.
 
 
 Search command history
 ++++++++++++++++++++++
 
 IPython provides two ways for searching through previous input and thus
 reduce the need for repetitive typing:
 
    1. Start typing, and then use Ctrl-p (previous,up) and Ctrl-n
       (next,down) to search through only the history items that match
       what you've typed so far. If you use Ctrl-p/Ctrl-n at a blank
       prompt, they just behave like normal arrow keys.
    2. Hit Ctrl-r: opens a search prompt. Begin typing and the system
       searches your history for lines that contain what you've typed so
       far, completing as much as it can.
 
 
 Persistent command history across sessions
 ++++++++++++++++++++++++++++++++++++++++++
 
 IPython will save your input history when it leaves and reload it next
 time you restart it. By default, the history file is named
 $IPYTHON_DIR/profile_<name>/history.sqlite. This allows you to keep
 separate histories related to various tasks: commands related to
 numerical work will not be clobbered by a system shell history, for
 example.
 
 
 Autoindent
 ++++++++++
 
 IPython can recognize lines ending in ':' and indent the next line,
 while also un-indenting automatically after 'raise' or 'return'.
 
 This feature uses the readline library, so it will honor your ~/.inputrc
 configuration (or whatever file your INPUTRC variable points to). Adding
 the following lines to your .inputrc file can make indenting/unindenting
 more convenient (M-i indents, M-u unindents)::
 
     $if Python 
     "\M-i": "    "  
     "\M-u": "\d\d\d\d"  
     $endif
 
 Note that there are 4 spaces between the quote marks after "M-i" above.
 
 .. warning::
 
     Setting the above indents will cause problems with unicode text entry in the terminal.
 
 .. warning::
 
-    This feature is ON by default, but it can cause problems with
+    Autoindent is ON by default, but it can cause problems with
     the pasting of multi-line indented code (the pasted code gets
     re-indented on each line). A magic function %autoindent allows you to
     toggle it on/off at runtime. You can also disable it permanently on in
     your :file:`ipython_config.py` file (set TerminalInteractiveShell.autoindent=False).
+    
+    If you want to paste multiple lines, it is recommended that you use ``%paste``.
 
 
 Customizing readline behavior
 +++++++++++++++++++++++++++++
 
 All these features are based on the GNU readline library, which has an
 extremely customizable interface. Normally, readline is configured via a
 file which defines the behavior of the library; the details of the
 syntax for this can be found in the readline documentation available
 with your system or on the Internet. IPython doesn't read this file (if
 it exists) directly, but it does support passing to readline valid
 options via a simple interface. In brief, you can customize readline by
 setting the following options in your ipythonrc configuration file (note
 that these options can not be specified at the command line):
 
     * **readline_parse_and_bind**: this option can appear as many times as
       you want, each time defining a string to be executed via a
       readline.parse_and_bind() command. The syntax for valid commands
       of this kind can be found by reading the documentation for the GNU
       readline library, as these commands are of the kind which readline
       accepts in its configuration file.
     * **readline_remove_delims**: a string of characters to be removed
       from the default word-delimiters list used by readline, so that
       completions may be performed on strings which contain them. Do not
       change the default value unless you know what you're doing.
     * **readline_omit__names**: when tab-completion is enabled, hitting
       <tab> after a '.' in a name will complete all attributes of an
       object, including all the special methods whose names include
       double underscores (like __getitem__ or __class__). If you'd
       rather not see these names by default, you can set this option to
       1. Note that even when this option is set, you can still see those
       names by explicitly typing a _ after the period and hitting <tab>:
       'name._<tab>' will always complete attribute names starting with '_'.
       
       This option is off by default so that new users see all
       attributes of any objects they are dealing with.
 
 You will find the default values along with a corresponding detailed
 explanation in your ipythonrc file.
 
 
 Session logging and restoring
 -----------------------------
 
 You can log all input from a session either by starting IPython with the
-command line switches -log or -logfile (see :ref:`here <command_line_options>`)
+command line switche ``logfile=foo.py`` (see :ref:`here <command_line_options>`)
 or by activating the logging at any moment with the magic function %logstart.
 
-Log files can later be reloaded with the -logplay option and IPython
+Log files can later be reloaded by running them as scripts and IPython
 will attempt to 'replay' the log by executing all the lines in it, thus
 restoring the state of a previous session. This feature is not quite
 perfect, but can still be useful in many cases.
 
 The log files can also be used as a way to have a permanent record of
 any code you wrote while experimenting. Log files are regular text files
 which you can later open in your favorite text editor to extract code or
 to 'clean them up' before using them to replay a session.
 
 The %logstart function for activating logging in mid-session is used as
 follows:
 
 %logstart [log_name [log_mode]]
 
-If no name is given, it defaults to a file named 'log' in your
-IPYTHON_DIR directory, in 'rotate' mode (see below).
+If no name is given, it defaults to a file named 'ipython_log.py' in your
+current working directory, in 'rotate' mode (see below).
 
 '%logstart name' saves to file 'name' in 'backup' mode. It saves your
 history up to that point and then continues logging.
 
 %logstart takes a second optional parameter: logging mode. This can be
 one of (note that the modes are given unquoted):
 
     * [over:] overwrite existing log_name.
     * [backup:] rename (if exists) to log_name~ and start log_name.
     * [append:] well, that says it.
     * [rotate:] create rotating logs log_name.1~, log_name.2~, etc.
 
 The %logoff and %logon functions allow you to temporarily stop and
 resume logging to a file which had previously been started with
 %logstart. They will fail (with an explanation) if you try to use them
 before logging has been started.
 
 .. _system_shell_access:
 
 System shell access
 -------------------
 
 Any input line beginning with a ! character is passed verbatim (minus
 the !, of course) to the underlying operating system. For example,
 typing !ls will run 'ls' in the current directory.
 
 Manual capture of command output
 --------------------------------
 
 If the input line begins with two exclamation marks, !!, the command is
 executed but its output is captured and returned as a python list, split
 on newlines. Any output sent by the subprocess to standard error is
 printed separately, so that the resulting list only captures standard
 output. The !! syntax is a shorthand for the %sx magic command.
 
 Finally, the %sc magic (short for 'shell capture') is similar to %sx,
 but allowing more fine-grained control of the capture details, and
 storing the result directly into a named variable. The direct use of 
 %sc is now deprecated, and you should ise the ``var = !cmd`` syntax
 instead.
 
 IPython also allows you to expand the value of python variables when
 making system calls. Any python variable or expression which you prepend
 with $ will get expanded before the system call is made::
 
     In [1]: pyvar='Hello world' 
     In [2]: !echo "A python variable: $pyvar"  
     A python variable: Hello world
 
 If you want the shell to actually see a literal $, you need to type it
 twice::
 
     In [3]: !echo "A system variable: $$HOME"  
     A system variable: /home/fperez
 
 You can pass arbitrary expressions, though you'll need to delimit them
 with {} if there is ambiguity as to the extent of the expression::
 
     In [5]: x=10 
     In [6]: y=20 
     In [13]: !echo $x+y  
     10+y  
     In [7]: !echo ${x+y}  
     30
 
 Even object attributes can be expanded::
 
     In [12]: !echo $sys.argv  
     [/home/fperez/usr/bin/ipython]
 
 
 System command aliases
 ----------------------
 
 The %alias magic function and the alias option in the ipythonrc
 configuration file allow you to define magic functions which are in fact
 system shell commands. These aliases can have parameters.
 
 '%alias alias_name cmd' defines 'alias_name' as an alias for 'cmd'
 
 Then, typing '%alias_name params' will execute the system command 'cmd
 params' (from your underlying operating system).
 
 You can also define aliases with parameters using %s specifiers (one per
 parameter). The following example defines the %parts function as an
 alias to the command 'echo first %s second %s' where each %s will be
 replaced by a positional parameter to the call to %parts::
 
     In [1]: alias parts echo first %s second %s 
     In [2]: %parts A B 
     first A second B  
     In [3]: %parts A  
     Incorrect number of arguments: 2 expected.  
     parts is an alias to: 'echo first %s second %s'
 
 If called with no parameters, %alias prints the table of currently
 defined aliases.
 
 The %rehash/rehashx magics allow you to load your entire $PATH as
 ipython aliases. See their respective docstrings (or sec. 6.2
 <#sec:magic> for further details).
 
 
 .. _dreload:
 
 Recursive reload
 ----------------
 
 The dreload function does a recursive reload of a module: changes made
 to the module since you imported will actually be available without
 having to exit.
 
 
 Verbose and colored exception traceback printouts
 -------------------------------------------------
 
 IPython provides the option to see very detailed exception tracebacks,
 which can be especially useful when debugging large programs. You can
 run any Python file with the %run function to benefit from these
 detailed tracebacks. Furthermore, both normal and verbose tracebacks can
 be colored (if your terminal supports it) which makes them much easier
 to parse visually.
 
 See the magic xmode and colors functions for details (just type %magic).
 
 These features are basically a terminal version of Ka-Ping Yee's cgitb
 module, now part of the standard Python library.
 
 
 .. _input_caching:
 
 Input caching system
 --------------------
 
 IPython offers numbered prompts (In/Out) with input and output caching
 (also referred to as 'input history'). All input is saved and can be 
 retrieved as variables (besides the usual arrow key recall), in 
 addition to the %rep magic command that brings a history entry
 up for editing on the next  command line.
 
 The following GLOBAL variables always exist (so don't overwrite them!):
 _i: stores previous input. _ii: next previous. _iii: next-next previous.
 _ih : a list of all input _ih[n] is the input from line n and this list
 is aliased to the global variable In. If you overwrite In with a
 variable of your own, you can remake the assignment to the internal list
 with a simple 'In=_ih'.
 
 Additionally, global variables named _i<n> are dynamically created (<n>
 being the prompt counter), such that
 _i<n> == _ih[<n>] == In[<n>].
 
 For example, what you typed at prompt 14 is available as _i14, _ih[14]
 and In[14].
 
 This allows you to easily cut and paste multi line interactive prompts
 by printing them out: they print like a clean string, without prompt
 characters. You can also manipulate them like regular variables (they
 are strings), modify or exec them (typing 'exec _i9' will re-execute the
 contents of input prompt 9, 'exec In[9:14]+In[18]' will re-execute lines
 9 through 13 and line 18).
 
 You can also re-execute multiple lines of input easily by using the
 magic %macro function (which automates the process and allows
 re-execution without having to type 'exec' every time). The macro system
 also allows you to re-execute previous lines which include magic
 function calls (which require special processing). Type %macro? or see
 sec. 6.2 <#sec:magic> for more details on the macro system.
 
 A history function %hist allows you to see any part of your input
 history by printing a range of the _i variables.
 
 You can also search ('grep') through your history by typing 
 '%hist -g somestring'. This also searches through the so called *shadow history*,
 which remembers all the commands (apart from multiline code blocks)
 you have ever entered. Handy for searching for svn/bzr URL's, IP adrresses
 etc. You can bring shadow history entries listed by '%hist -g' up for editing 
 (or re-execution by just pressing ENTER) with %rep command. Shadow history 
 entries are not available as _iNUMBER variables, and they are identified by 
 the '0' prefix in %hist -g output. That is, history entry 12 is a normal 
 history entry, but 0231 is a shadow history entry.
 
 Shadow history was added because the readline history is inherently very
 unsafe - if you have multiple IPython sessions open, the last session 
 to close will overwrite the history of previountly closed session. Likewise,
 if a crash occurs, history is never saved, whereas shadow history entries
 are added after entering every command (so a command executed 
 in another IPython session is immediately available in other IPython 
 sessions that are open).
 
 To conserve space, a command can exist in shadow history only once - it doesn't 
 make sense to store a common line like "cd .." a thousand times. The idea is 
 mainly to provide a reliable place where valuable, hard-to-remember commands can 
 always be retrieved, as opposed to providing an exact sequence of commands
 you have entered in actual order.
 
 Because shadow history has all the commands you have ever executed,
 time taken by %hist -g will increase oven time. If it ever starts to take
 too long (or it ends up containing sensitive information like passwords), 
 clear the shadow history by `%clear shadow_nuke`.
 
 Time taken to add entries to shadow history should be negligible, but 
 in any case, if you start noticing performance degradation after using 
 IPython for a long time (or running a script that floods the shadow history!), 
 you can 'compress' the shadow history by executing 
 `%clear shadow_compress`. In practice, this should never be necessary
 in normal use.
 
 .. _output_caching:
 
 Output caching system
 ---------------------
 
 For output that is returned from actions, a system similar to the input
 cache exists but using _ instead of _i. Only actions that produce a
 result (NOT assignments, for example) are cached. If you are familiar
 with Mathematica, IPython's _ variables behave exactly like
 Mathematica's % variables.
 
 The following GLOBAL variables always exist (so don't overwrite them!):
 
     * [_] (a single underscore) : stores previous output, like Python's
       default interpreter.
     * [__] (two underscores): next previous.
     * [___] (three underscores): next-next previous.
 
 Additionally, global variables named _<n> are dynamically created (<n>
 being the prompt counter), such that the result of output <n> is always
 available as _<n> (don't use the angle brackets, just the number, e.g.
 _21).
 
 These global variables are all stored in a global dictionary (not a
 list, since it only has entries for lines which returned a result)
 available under the names _oh and Out (similar to _ih and In). So the
 output from line 12 can be obtained as _12, Out[12] or _oh[12]. If you
 accidentally overwrite the Out variable you can recover it by typing
 'Out=_oh' at the prompt.
 
 This system obviously can potentially put heavy memory demands on your
 system, since it prevents Python's garbage collector from removing any
 previously computed results. You can control how many results are kept
 in memory with the option (at the command line or in your ipythonrc
 file) cache_size. If you set it to 0, the whole system is completely
 disabled and the prompts revert to the classic '>>>' of normal Python.
 
 
 Directory history
 -----------------
 
 Your history of visited directories is kept in the global list _dh, and
 the magic %cd command can be used to go to any entry in that list. The
 %dhist command allows you to view this history. Do ``cd -<TAB`` to
-conventiently view the directory history.
+conveniently view the directory history.
 
 
 Automatic parentheses and quotes
 --------------------------------
 
 These features were adapted from Nathan Gray's LazyPython. They are
 meant to allow less typing for common situations.
 
 
 Automatic parentheses
 ---------------------
 
 Callable objects (i.e. functions, methods, etc) can be invoked like this
 (notice the commas between the arguments)::
 
     >>> callable_ob arg1, arg2, arg3
 
 and the input will be translated to this::
 
     -> callable_ob(arg1, arg2, arg3)
 
 You can force automatic parentheses by using '/' as the first character
 of a line. For example::
 
     >>> /globals # becomes 'globals()'
 
 Note that the '/' MUST be the first character on the line! This won't work::
 
     >>> print /globals # syntax error
 
 In most cases the automatic algorithm should work, so you should rarely
 need to explicitly invoke /. One notable exception is if you are trying
 to call a function with a list of tuples as arguments (the parenthesis
 will confuse IPython)::
 
     In [1]: zip (1,2,3),(4,5,6) # won't work
 
 but this will work::
 
     In [2]: /zip (1,2,3),(4,5,6) 
     ---> zip ((1,2,3),(4,5,6))  
     Out[2]= [(1, 4), (2, 5), (3, 6)]
 
 IPython tells you that it has altered your command line by displaying
 the new command line preceded by ->. e.g.::
 
     In [18]: callable list 
     ----> callable (list)
 
 
 Automatic quoting
 -----------------
 
 You can force automatic quoting of a function's arguments by using ','
 or ';' as the first character of a line. For example::
 
     >>> ,my_function /home/me # becomes my_function("/home/me")
 
 If you use ';' instead, the whole argument is quoted as a single string
 (while ',' splits on whitespace)::
 
     >>> ,my_function a b c # becomes my_function("a","b","c")
 
     >>> ;my_function a b c # becomes my_function("a b c")
 
 Note that the ',' or ';' MUST be the first character on the line! This
 won't work::
 
     >>> x = ,my_function /home/me # syntax error
 
 IPython as your default Python environment
 ==========================================
 
 Python honors the environment variable PYTHONSTARTUP and will execute at
 startup the file referenced by this variable. If you put at the end of
 this file the following two lines of code::
 
     from IPython.frontend.terminal.ipapp import launch_new_instance
     launch_new_instance()
     raise SystemExit
 
 then IPython will be your working environment anytime you start Python.
 The ``raise SystemExit`` is needed to exit Python when
 it finishes, otherwise you'll be back at the normal Python '>>>'
 prompt.
 
 This is probably useful to developers who manage multiple Python
 versions and don't want to have correspondingly multiple IPython
 versions. Note that in this mode, there is no way to pass IPython any
 command-line options, as those are trapped first by Python itself.
 
 .. _Embedding:
 
 Embedding IPython
 =================
 
 It is possible to start an IPython instance inside your own Python
 programs. This allows you to evaluate dynamically the state of your
 code, operate with your variables, analyze them, etc. Note however that
 any changes you make to values while in the shell do not propagate back
 to the running code, so it is safe to modify your values because you
 won't break your code in bizarre ways by doing so.
 
 This feature allows you to easily have a fully functional python
 environment for doing object introspection anywhere in your code with a
 simple function call. In some cases a simple print statement is enough,
 but if you need to do more detailed analysis of a code fragment this
 feature can be very valuable.
 
 It can also be useful in scientific computing situations where it is
 common to need to do some automatic, computationally intensive part and
 then stop to look at data, plots, etc.
 Opening an IPython instance will give you full access to your data and
 functions, and you can resume program execution once you are done with
 the interactive part (perhaps to stop again later, as many times as
 needed).
 
 The following code snippet is the bare minimum you need to include in
 your Python programs for this to work (detailed examples follow later)::
 
     from IPython import embed
 
     embed() # this call anywhere in your program will start IPython
 
 You can run embedded instances even in code which is itself being run at
 the IPython interactive prompt with '%run <filename>'. Since it's easy
 to get lost as to where you are (in your top-level IPython or in your
 embedded one), it's a good idea in such cases to set the in/out prompts
 to something different for the embedded instances. The code examples
 below illustrate this.
 
 You can also have multiple IPython instances in your program and open
 them separately, for example with different options for data
 presentation. If you close and open the same instance multiple times,
 its prompt counters simply continue from each execution to the next.
 
 Please look at the docstrings in the :mod:`~IPython.frontend.terminal.embed` 
 module for more details on the use of this system.
 
 The following sample file illustrating how to use the embedding
 functionality is provided in the examples directory as example-embed.py.
 It should be fairly self-explanatory:
 
 .. literalinclude:: ../../examples/core/example-embed.py
     :language: python
 
 Once you understand how the system functions, you can use the following
 code fragments in your programs which are ready for cut and paste:
 
 .. literalinclude:: ../../examples/core/example-embed-short.py
     :language: python
 
 Using the Python debugger (pdb)
 ===============================
 
 Running entire programs via pdb
 -------------------------------
 
 pdb, the Python debugger, is a powerful interactive debugger which
 allows you to step through code, set breakpoints, watch variables,
 etc.  IPython makes it very easy to start any script under the control
 of pdb, regardless of whether you have wrapped it into a 'main()'
 function or not. For this, simply type '%run -d myscript' at an
 IPython prompt. See the %run command's documentation (via '%run?' or
 in Sec. magic_ for more details, including how to control where pdb
 will stop execution first.
 
 For more information on the use of the pdb debugger, read the included
 pdb.doc file (part of the standard Python distribution). On a stock
 Linux system it is located at /usr/lib/python2.3/pdb.doc, but the
 easiest way to read it is by using the help() function of the pdb module
 as follows (in an IPython prompt)::
 
     In [1]: import pdb
     In [2]: pdb.help()
 
 This will load the pdb.doc document in a file viewer for you automatically.
 
 
 Automatic invocation of pdb on exceptions
 -----------------------------------------
 
 IPython, if started with the -pdb option (or if the option is set in
 your rc file) can call the Python pdb debugger every time your code
 triggers an uncaught exception. This feature
 can also be toggled at any time with the %pdb magic command. This can be
 extremely useful in order to find the origin of subtle bugs, because pdb
 opens up at the point in your code which triggered the exception, and
 while your program is at this point 'dead', all the data is still
 available and you can walk up and down the stack frame and understand
 the origin of the problem.
 
 Furthermore, you can use these debugging facilities both with the
 embedded IPython mode and without IPython at all. For an embedded shell
 (see sec. Embedding_), simply call the constructor with
 '--pdb' in the argument string and automatically pdb will be called if an
 uncaught exception is triggered by your code.
 
 For stand-alone use of the feature in your programs which do not use
 IPython at all, put the following lines toward the top of your 'main'
 routine::
 
     import sys
     from IPython.core import ultratb
     sys.excepthook = ultratb.FormattedTB(mode='Verbose',
     color_scheme='Linux', call_pdb=1)
 
 The mode keyword can be either 'Verbose' or 'Plain', giving either very
 detailed or normal tracebacks respectively. The color_scheme keyword can
 be one of 'NoColor', 'Linux' (default) or 'LightBG'. These are the same
 options which can be set in IPython with -colors and -xmode.
 
 This will give any of your programs detailed, colored tracebacks with
 automatic invocation of pdb.
 
 
 Extensions for syntax processing
 ================================
 
 This isn't for the faint of heart, because the potential for breaking
 things is quite high. But it can be a very powerful and useful feature.
 In a nutshell, you can redefine the way IPython processes the user input
 line to accept new, special extensions to the syntax without needing to
 change any of IPython's own code.
 
 In the IPython/extensions directory you will find some examples
 supplied, which we will briefly describe now. These can be used 'as is'
 (and both provide very useful functionality), or you can use them as a
 starting point for writing your own extensions.
 
 
 Pasting of code starting with '>>> ' or '... '
 ----------------------------------------------
 
 In the python tutorial it is common to find code examples which have
 been taken from real python sessions. The problem with those is that all
 the lines begin with either '>>> ' or '... ', which makes it impossible
 to paste them all at once. One must instead do a line by line manual
 copying, carefully removing the leading extraneous characters.
 
 This extension identifies those starting characters and removes them
 from the input automatically, so that one can paste multi-line examples
 directly into IPython, saving a lot of time. Please look at the file
 InterpreterPasteInput.py in the IPython/extensions directory for details
 on how this is done.
 
 IPython comes with a special profile enabling this feature, called
 tutorial. Simply start IPython via 'ipython -p tutorial' and the feature
 will be available. In a normal IPython session you can activate the
 feature by importing the corresponding module with:
 In [1]: import IPython.extensions.InterpreterPasteInput
 
 The following is a 'screenshot' of how things work when this extension
 is on, copying an example from the standard tutorial::
 
     IPython profile: tutorial 
 
     *** Pasting of code with ">>>" or "..." has been enabled. 
 
     In [1]: >>> def fib2(n): # return Fibonacci series up to n 
        ...: ...     """Return a list containing the Fibonacci series up to
     n.""" 
        ...: ...     result = [] 
        ...: ...     a, b = 0, 1 
        ...: ...     while b < n: 
        ...: ...         result.append(b)    # see below 
        ...: ...         a, b = b, a+b 
        ...: ...     return result 
        ...: 
 
     In [2]: fib2(10) 
     Out[2]: [1, 1, 2, 3, 5, 8]
 
 Note that as currently written, this extension does not recognize
 IPython's prompts for pasting. Those are more complicated, since the
 user can change them very easily, they involve numbers and can vary in
 length. One could however extract all the relevant information from the
 IPython instance and build an appropriate regular expression. This is
 left as an exercise for the reader.
 
 
 Input of physical quantities with units
 ---------------------------------------
 
 The module PhysicalQInput allows a simplified form of input for physical
 quantities with units. This file is meant to be used in conjunction with
 the PhysicalQInteractive module (in the same directory) and
 Physics.PhysicalQuantities from Konrad Hinsen's ScientificPython
 (http://dirac.cnrs-orleans.fr/ScientificPython/).
 
 The Physics.PhysicalQuantities module defines PhysicalQuantity objects,
 but these must be declared as instances of a class. For example, to
 define v as a velocity of 3 m/s, normally you would write::
 
     In [1]: v = PhysicalQuantity(3,'m/s')
 
 Using the PhysicalQ_Input extension this can be input instead as: 
 In [1]: v = 3 m/s
 which is much more convenient for interactive use (even though it is
 blatantly invalid Python syntax).
 
 The physics profile supplied with IPython (enabled via 'ipython -p
 physics') uses these extensions, which you can also activate with:
 
 from math import * # math MUST be imported BEFORE PhysicalQInteractive 
 from IPython.extensions.PhysicalQInteractive import * 
 import IPython.extensions.PhysicalQInput
 
 .. _gui_support:
 
 GUI event loop support support
 ==============================
 
 .. versionadded:: 0.11
     The ``%gui`` magic and :mod:`IPython.lib.inputhook`.
 
 IPython has excellent support for working interactively with Graphical User
 Interface (GUI) toolkits, such as wxPython, PyQt4, PyGTK and Tk. This is
 implemented using Python's builtin ``PyOSInputHook`` hook. This implementation
 is extremely robust compared to our previous threaded based version. The
 advantages of this are:
 
 * GUIs can be enabled and disabled dynamically at runtime.
 * The active GUI can be switched dynamically at runtime.
 * In some cases, multiple GUIs can run simultaneously with no problems.
 * There is a developer API in :mod:`IPython.lib.inputhook` for customizing 
   all of these things.
 
 For users, enabling GUI event loop integration is simple.  You simple use the
 ``%gui`` magic as follows::
 
     %gui [-a] [GUINAME]
 
 With no arguments, ``%gui`` removes all GUI support.  Valid ``GUINAME``
 arguments are ``wx``, ``qt4``, ``gtk`` and ``tk``.  The ``-a`` option will
 create and return a running application object for the selected GUI toolkit.
 
 Thus, to use wxPython interactively and create a running :class:`wx.App`
 object, do::
 
     %gui -a wx
 
 For information on IPython's Matplotlib integration (and the ``pylab`` mode)
 see :ref:`this section <matplotlib_support>`.
 
 For developers that want to use IPython's GUI event loop integration in
 the form of a library, these capabilities are exposed in library form
 in the :mod:`IPython.lib.inputhook`.  Interested developers should see the
 module docstrings for more information, but there are a few points that
 should be mentioned here.
 
 First, the ``PyOSInputHook`` approach only works in command line settings 
 where readline is activated.
 
 Second, when using the ``PyOSInputHook`` approach, a GUI application should
 *not* start its event loop. Instead all of this is handled by the
 ``PyOSInputHook``. This means that applications that are meant to be used both
 in IPython and as standalone apps need to have special code to detects how the
 application is being run. We highly recommend using IPython's
 :func:`enable_foo` functions for this. Here is a simple example that shows the
 recommended code that should be at the bottom of a wxPython using GUI
 application::
 
   try:
       from IPython.lib.inputhook import enable_wx
       enable_wx(app)
   except ImportError:
       app.MainLoop()
 
 This pattern should be used instead of the simple ``app.MainLoop()`` code
 that a standalone wxPython application would have.
 
 Third, unlike previous versions of IPython, we no longer "hijack" (replace
 them with no-ops) the event loops. This is done to allow applications that
 actually need to run the real event loops to do so. This is often needed to
 process pending events at critical points.
 
 Finally, we also have a number of examples in our source directory
 :file:`docs/examples/lib` that demonstrate these capabilities.
 
 .. _matplotlib_support:
 
 Plotting with matplotlib
 ========================
 
 
 `Matplotlib`_ provides high quality 2D and
 3D plotting for Python. Matplotlib can produce plots on screen using a variety
 of GUI toolkits, including Tk, PyGTK, PyQt4 and wxPython. It also provides a
 number of commands useful for scientific computing, all with a syntax
 compatible with that of the popular Matlab program.
 
 Many IPython users have come to rely on IPython's ``-pylab`` mode which
 automates the integration of Matplotlib with IPython. We are still in the
 process of working with the Matplotlib developers to finalize the new pylab
 API, but for now you can use Matplotlib interactively using the following
 commands::
 
     %gui -a wx
     import matplotlib
     matplotlib.use('wxagg')
     from matplotlib import pylab
     pylab.interactive(True)
 
 All of this will soon be automated as Matplotlib begins to include
 new logic that uses our new GUI support.
 
 .. _Matplotlib: http://matplotlib.sourceforge.net
 
 .. _interactive_demos:
 
 Interactive demos with IPython
 ==============================
 
 IPython ships with a basic system for running scripts interactively in
 sections, useful when presenting code to audiences. A few tags embedded
 in comments (so that the script remains valid Python code) divide a file
 into separate blocks, and the demo can be run one block at a time, with
 IPython printing (with syntax highlighting) the block before executing
 it, and returning to the interactive prompt after each block. The
 interactive namespace is updated after each block is run with the
 contents of the demo's namespace.
 
 This allows you to show a piece of code, run it and then execute
 interactively commands based on the variables just created. Once you
 want to continue, you simply execute the next block of the demo. The
 following listing shows the markup necessary for dividing a script into
 sections for execution as a demo:
 
 .. literalinclude:: ../../examples/lib/example-demo.py
     :language: python
 
 
 In order to run a file as a demo, you must first make a Demo object out
 of it. If the file is named myscript.py, the following code will make a
 demo::
 
     from IPython.lib.demo import Demo
 
     mydemo = Demo('myscript.py')
 
 This creates the mydemo object, whose blocks you run one at a time by
 simply calling the object with no arguments. If you have autocall active
 in IPython (the default), all you need to do is type::
 
     mydemo 
 
 and IPython will call it, executing each block. Demo objects can be
 restarted, you can move forward or back skipping blocks, re-execute the
 last block, etc. Simply use the Tab key on a demo object to see its
 methods, and call '?' on them to see their docstrings for more usage
 details. In addition, the demo module itself contains a comprehensive
 docstring, which you can access via::
 
     from IPython.lib import demo
 
     demo?
 
 Limitations: It is important to note that these demos are limited to
 fairly simple uses. In particular, you can not put division marks in
 indented code (loops, if statements, function definitions, etc.)
 Supporting something like this would basically require tracking the
 internal execution state of the Python interpreter, so only top-level
 divisions are allowed. If you want to be able to open an IPython
 instance at an arbitrary point in a program, you can use IPython's
 embedding facilities, described in detail in Sec. 9