1 .. Objectives

     2 .. ----------

     3 

     4 .. By the end of this tutorial you will be able to

     5 

     6 .. #. Retrieve your ipython history 

     7 .. #. View a part of the history 

     8 .. #. Save a part of your history to a file. 

     9 .. #. Run a script from within ipython 

    10 

    11 

    12 .. Prerequisites

    13 .. -------------

    14 

    15 ..   1. Embellishing Plots

    16      

    17 .. Author              : Nishanth Amuluru

    18    Internal Reviewer   : Amit

    19    External Reviewer   :

    20    Language Reviewer   : Bhanukiran

    21    Checklist OK?       : <15-11-2010, Anand, OK> [2010-10-05]

    22 

    23 Script

    24 ------

    25 

    26 Hello friends and welcome to the tutorial on Additional Features of IPython

    27 

    28 {{{ Show the slide containing title }}}

    29 

    30 {{{ Show the slide containing the outline slide }}}

    31 

    32 In this tutorial, we shall look at additional features of IPython that help us

    33 to retreive the commands that we type on the interpreter and then save them

    34 into a file and run it.

    35 

    36 Let us start ipython with pylab loaded, by typing

    37 ::

    38 

    39     $ ipython -pylab

    40 

    41 on the terminal

    42 

    43 {{{ shift to terminal and type ipython -pylab }}}

    44 

    45 We shall first make a plot and then view the history and save it.

    46 ::

    47 

    48     x = linspace(-2*pi, 2*pi, 100)

    49     plot(x, xsinx(x))

    50 

    51 xsin(x) is actually x * sin(x)

    52 ::

    53 

    54     plot(x, x*sin(x))

    55     plot(x, sin(x))

    56     xlabel("x")

    57     ylabel("$f(x)$")   

    58     title("x and xsin")

    59 

    60 We now have the plot. Let us look at the commands that we have typed in. The

    61 history can be retreived by using =%hist= command. Type

    62 ::

    63 

    64     %hist

    65 

    66 As you can see, it displays a list of recent commands that we typed. Every

    67 command has a number in front, to specify in which order and when it was typed.

    68 

    69 Please note that there is a % sign before the hist command. This implies that 

    70 %hist is a command that is specific to IPython and not available in the vannila 

    71 Python interpreter. These type of commands are called as magic commands.

    72 

    73 Also note that, the =%hist= itself is a command and is displayed as the most

    74 recent command. We should not that anything we type in is stored as history, 

    75 irrespective of whether it is command or an error or IPython magic command.

    76 

    77 If we want only the recent 5 commands to be displayed, we pass the number as an argument

    78 to =%hist= command. Hence

    79 ::

    80 

    81     %hist 5 

    82 

    83 displays the recent 5 commands, inclusive of the =%hist= command.

    84 The default number is 40.

    85 

    86 {{{ Pause here and try out the following exercises }}}

    87 

    88 %% 1 %% Read through the documentation of %hist and find out how to

    89         list all the commands between 5 and 10

    90 

    91 {{{ continue from paused state }}}

    92 

    93 As we can see from =%hist= documentation,

    94 ::

    95 

    96     %hist 5 10

    97 

    98 displays the commands from 5 to 10

    99 

   100 Now that we have the history, we would like to save the required line of code

   101 from history. This is possible by using the =%save= command.

   102 

   103 Before we do that, let us first look at history and identify what lines of code we require.Type

   104 ::

   105 

   106     %hist

   107 

   108 

   109 {{{ point to the lines }}}

   110 

   111 The first command is linspace. But second command is a command that gave us an

   112 error. Hence we do not need second command. The commands from third to sixth are 

   113 required. The seventh command although is correct, we do not need it since we

   114 are setting the title correctly in the eigthth command.

   115 

   116 So we need first third to sixth and the eigthth command for our program.

   117 Hence the syntax of =%save= is

   118 ::

   119 

   120     %save /home/fossee/plot_script.py 1 3-6 8

   121 

   122 {{{ point to the output of the command }}}

   123 

   124 The command saves first and then third to sixth and eighth lines of code into

   125 the specified file.

   126 

   127 The first argument to %save is the path of file to save the commands and the

   128 arguments there after are the commands to be saved in the given order.

   129 

   130 {{{ goto the file and open it and show it }}}

   131 

   132 {{{ Pause here and try out the following exercises }}}

   133 

   134 %% 2 %% Change the label on y-axis to "y" and save the lines of code

   135         accordingly

   136 

   137 {{{ continue from paused state }}}

   138 

   139 we use the command =ylabel= on interpreter as

   140 ::

   141 

   142     ylabel("y")

   143 

   144 and then do

   145 ::

   146 

   147     %save /home/fossee/example_plot.py 1 3-6 10

   148 

   149 Now that we have the required lines of code in a file, let us learn how to run

   150 the file as a python script.

   151 

   152 We use the IPython magic command =%run= to do this. Type

   153 ::

   154 

   155    %run -i /home/fossee/plot_script.py

   156 

   157 The script runs but we do not see the plot. This happens because when we are running

   158 a script and we are not in interactive mode anymore.

   159 

   160 Hence on your terminal type

   161 ::

   162 

   163     show()

   164 

   165 to show the plot.

   166 

   167 {{{ Pause here and try out the following exercises }}}

   168 

   169 %% 3 %% Use %hist and %save and create a script that has show in it and run it

   170         to produce and show the plot.

   171 

   172 

   173 {{{ continue from paused state }}}

   174 

   175 We first look at the history using

   176 ::

   177 

   178     %hist 20

   179 

   180 Then save the script using

   181 ::

   182 

   183     %save /home/fossee/show_included.py 1 3-6 8 10 13

   184     %run -i /home/fossee/show_included.py

   185     show()    

   186 

   187 We get the desired plot.

   188 

   189 The reason for including a -i after run is to tell the interpreter that if any

   190 name is not found in script, search for it in the interpreter. Hence all these

   191 sin, plot, pi and show which are not available in script, are taken from the

   192 interpreter and used to run the script.

   193 

   194 {{{ Pause here and try out the following exercises }}}

   195 

   196 %% 4 %% Run the script without using the -i option. Do you find any difference?

   197 

   198 {{{ continue from paused state }}}

   199 

   200 We see that it raises NameError saying that the name linspace is not found.

   201 

   202 {{{ Show summary slide }}}

   203 

   204 This brings us to the end of the tutorial.

   205 we have looked at 

   206 

   207  * Retreiving history using =%hist= command

   208  * Vieweing only a part of history by passing an argument to %hist

   209  * saving the required lines of code in required order using %save

   210  * using %run -i command to run the saved script

   211 

   212 {{{ Show the "sponsored by FOSSEE" slide }}}

   213 

   214 

   215 This tutorial was created as a part of FOSSEE project, NME ICT, MHRD India

   216 

   217 Hope you have enjoyed and found it useful.

   218 Thank You!

   219