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docs/source/interactive/tutorial.rst

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 .. _tutorial:
 
 ======================
 Introducing IPython
 ======================
 
 You don't need to know anything beyond Python to start using IPython – just type
 commands as you would at the standard Python prompt. But IPython can do much
 more than the standard prompt. Some key features are described here. For more
 information, check the :ref:`tips page <tips>`, or look at examples in the
 `IPython cookbook <https://github.com/ipython/ipython/wiki/Cookbook%3A-Index>`_.
 
 If you haven't done that yet see `how to install ipython <install>`_ .
 
 If you've never used Python before, you might want to look at `the official
 tutorial <http://docs.python.org/tutorial/>`_ or an alternative, `Dive into
 Python <http://diveintopython.net/toc/index.html>`_.
 
 Start IPython by issuing the ``ipython`` command from your shell, you should be
 greeted by the following::
 
     Python 3.6.0
     Type 'copyright', 'credits' or 'license' for more information
     IPython 6.0.0.dev -- An enhanced Interactive Python. Type '?' for help.
 
     In [1]:
 
 
 Unlike the Python REPL, you will see that the input prompt is ``In [N]:``
 instead of ``>>>``. The number ``N`` in the prompt will be used later in this
 tutorial but should usually not impact the computation.
 
 You should be able to type single line expressions and press enter to evaluate
 them. If an expression is incomplete, IPython will automatically detect this and
-add a new line when you press ``Enter`` instead of evaluating.
+add a new line when you press ``Enter`` instead of executing right away.
 
-Feel free to explore multi-line text edition. Unlike many other REPL with
+Feel free to explore multi-line text input. Unlike many other REPLs, with
 IPython you can use the up and down arrow keys when editing multi-line
 code blocks.
 
-Here is an example of a longer interaction with the IPython REPL we often refer
-to as an IPython _session_ ::
+Here is an example of a longer interaction with the IPython REPL,
+which we often refer to as an IPython _session_ ::
 
     In [1]: print('Hello IPython')
     Hello IPython
 
     In [2]: 21 * 2
     Out[2]: 42
 
     In [3]: def say_hello(name):
        ...:     print('Hello {name}'.format(name=name))
        ...:
 
-We won't get into details right now, but unlike the standard python REPL you
-will notice a few difference. First your code should be syntax-highlighted as
-you type.
-
+We won't get into details right now, but you may notice a few differences to the standard Python REPL.
+First, your code should be syntax-highlighted as you type.
 Second, you will see that some results will have an ``Out[N]:`` prompt, while
 some other do not. We'll come to this later.
 
 The four most helpful commands
 ==============================
 
 The four most helpful commands, as well as their brief description, is shown
 to you in a banner, every time you start IPython:
 
 ==========    =========================================================
 command       description
 ==========    =========================================================
 ?             Introduction and overview of IPython's features.
 %quickref     Quick reference.
 help          Python's own help system.
 object?       Details about 'object', use 'object??' for extra details.
 ==========    =========================================================
 
 Tab completion
 ==============
 
 Tab completion, especially for attributes, is a convenient way to explore the
 structure of any object you're dealing with. Simply type ``object_name.<TAB>``
 to view the object's attributes. Besides Python objects and keywords, tab
 completion also works on file and directory names.
 
 Exploring your objects
 ======================
 
 Typing ``object_name?`` will print all sorts of details about any object,
 including docstrings, function definition lines (for call arguments) and
 constructor details for classes. To get specific information on an object, you
 can use the magic commands ``%pdoc``, ``%pdef``, ``%psource`` and ``%pfile``
 
 .. _magics_explained:
 
 Magic functions
 ===============
 
 IPython has a set of predefined 'magic functions' that you can call with a
 command line style syntax.  There are two kinds of magics, line-oriented and
 cell-oriented.  **Line magics** are prefixed with the ``%`` character and work
 much like OS command-line calls: they get as an argument the rest of the line,
 where arguments are passed without parentheses or quotes. **Lines magics** can
 return results and can be used in the right hand side of an assignment.  **Cell
 magics** are prefixed with a double ``%%``, and they are functions that get as
 an argument not only the rest of the line, but also the lines below it in a
 separate argument.
 
 Magics are useful as convenient functions where Python syntax is not the most
 natural one, or when one want to embed invalid python syntax in their work flow. 
 
 The following examples show how to call the builtin :magic:`timeit` magic, both
 in line and cell mode::
 
       In [1]: %timeit range(1000)
       100000 loops, best of 3: 7.76 us per loop
 
       In [2]: %%timeit x = range(10000)
       ...: max(x)
       ...: 
       1000 loops, best of 3: 223 us per loop
 
 The builtin magics include:
 
 - Functions that work with code: :magic:`run`, :magic:`edit`, :magic:`save`,
   :magic:`macro`, :magic:`recall`, etc.
 
 - Functions which affect the shell: :magic:`colors`, :magic:`xmode`,
   :magic:`autoindent`, :magic:`automagic`, etc.
 
 - Other functions such as :magic:`reset`, :magic:`timeit`,
   :cellmagic:`writefile`, :magic:`load`, or :magic:`paste`.
 
 You can always call magics using the ``%`` prefix, and if you're calling a line
 magic on a line by itself, as long as the identifier is not defined in your
 namespace, you can omit even that::
 
     run thescript.py
 
 You can toggle this behavior by running the :magic:`automagic` magic.  Cell
 magics must always have the ``%%`` prefix.
 
 A more detailed explanation of the magic system can be obtained by calling
 ``%magic``, and for more details on any magic function, call ``%somemagic?`` to
 read its docstring. To see all the available magic functions, call
 ``%lsmagic``.
 
 .. seealso::
 
     The :ref:`magic` section of the documentation goes more in depth into how
     the magics works and how to define your own, and :doc:`magics` for a list of
     built-in magics.
 
     `Cell magics`_ example notebook
 
 Running and Editing
 -------------------
 
 The :magic:`run` magic command allows you to run any python script and load all
 of its data directly into the interactive namespace. Since the file is re-read
 from disk each time, changes you make to it are reflected immediately (unlike
 imported modules, which have to be specifically reloaded). IPython also includes
 :ref:`dreload <dreload>`, a recursive reload function.
 
 ``%run`` has special flags for timing the execution of your scripts (-t), or
 for running them under the control of either Python's pdb debugger (-d) or
 profiler (-p).
 
 The :magic:`edit` command gives a reasonable approximation of multiline editing,
 by invoking your favorite editor on the spot. IPython will execute the
 code you type in there as if it were typed interactively. Note that for
 :magic:`edit` to work, the call to startup your editor has to be a blocking
 call. In a GUI environment, your editor likely will have such an option.
 
 Debugging
 ---------
 
 After an exception occurs, you can call :magic:`debug` to jump into the Python
 debugger (pdb) and examine the problem. Alternatively, if you call :magic:`pdb`,
 IPython will automatically start the debugger on any uncaught exception. You can
 print variables, see code, execute statements and even walk up and down the call
 stack to track down the true source of the problem. This can be an efficient way
 to develop and debug code, in many cases eliminating the need for print
 statements or external debugging tools.
 
 You can also step through a program from the beginning by calling
 ``%run -d theprogram.py``.
 
 History
 =======
 
 IPython stores both the commands you enter, and the results it produces. You
 can easily go through previous commands with the up- and down-arrow keys, or
 access your history in more sophisticated ways.
 
 Input and output history are kept in variables called ``In`` and ``Out``, keyed
 by the prompt numbers, e.g. ``In[4]``. The last three objects in output history
 are also kept in variables named ``_``, ``__`` and ``___``.
 
 You can use the ``%history`` magic function to examine past input and output.
 Input history from previous sessions is saved in a database, and IPython can be
 configured to save output history.
 
 Several other magic functions can use your input history, including ``%edit``, 
 ``%rerun``, ``%recall``, ``%macro``, ``%save`` and ``%pastebin``. You can use a
 standard format to refer to lines::
 
     %pastebin 3 18-20 ~1/1-5
     
 This will take line 3 and lines 18 to 20 from the current session, and lines
 1-5 from the previous session.
 
 System shell commands
 =====================
 
 To run any command at the system shell, simply prefix it with ``!``, e.g.::
 
     !ping www.bbc.co.uk
     
 You can capture the output into a Python list, e.g.: ``files = !ls``. To pass
 the values of Python variables or expressions to system commands, prefix them
 with $: ``!grep -rF $pattern ipython/*``. See :ref:`our shell section
 <system_shell_access>` for more details.
 
 Define your own system aliases
 ------------------------------
 
 It's convenient to have aliases to the system commands you use most often. This
 allows you to work seamlessly from inside IPython with the same commands you are
 used to in your system shell. IPython comes with some pre-defined aliases and a
 complete system for changing directories, both via a stack (see :magic:`pushd`,
 :magic:`popd` and :magic:`dhist`) and via direct :magic:`cd`. The latter keeps a
 history of visited directories and allows you to go to any previously visited
 one.
 
 
 Configuration
 =============
 
 Much of IPython can be tweaked through :doc:`configuration </config/intro>`.
 To get started, use the command ``ipython profile create`` to produce the
 default config files. These will be placed in
 :file:`~/.ipython/profile_default`, and contain comments explaining
 what the various options do.
 
 Profiles allow you to use IPython for different tasks, keeping separate config
 files and history for each one. More details in :ref:`the profiles section
 <profiles>`.
 
 .. _startup_files:
 
 Startup Files
 -------------
 
 If you want some code to be run at the beginning of every IPython session, the
 easiest way is to add Python (.py) or IPython (.ipy) scripts to your
 :file:`profile_default/startup/` directory. Files here will be executed as soon
 as the IPython shell is constructed, before any other code or scripts you have
 specified. The files will be run in order of their names, so you can control the
 ordering with prefixes, like ``10-myimports.py``.
 
 .. include:: ../links.txt