1 .. Objectives

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

     3 

     4 .. A - Students and teachers from Science and engineering backgrounds

     5    B - 

     6    C - 

     7    D - 

     8 

     9 .. Prerequisites

    10 .. -------------

    11 

    12 ..   1. Embellishing Plots

    13      

    14 .. Author              : Nishanth Amuluru

    15    Internal Reviewer   : 

    16    External Reviewer   :

    17    Checklist OK?       : <put date stamp here, if OK> [2010-10-05]

    18 

    19 Script

    20 ------

    21 

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

    23 

    24 {{{ Show the slide containing title }}}

    25 

    26 {{{ Show the slide containing the outline slide }}}

    27 

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

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

    30 into a file and run it.

    31 

    32 Let us start ipython with pylab loaded, by typing

    33 ::

    34 

    35     $ ipython -pylab

    36 

    37 on the terminal

    38 

    39 {{{ shit to terminal and type ipython -pylab }}}

    40 

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

    42 ::

    43 

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

    45     plot(x, xsinx(x))

    46 

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

    48 ::

    49 

    50     plot(x, x*sin(x))

    51     plot(x, sin(x))

    52     xlabel("x")

    53     ylabel("$f(x)$")   

    54     title("x and xsin")

    55 

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

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

    58 ::

    59 

    60     %hist

    61 

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

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

    64 

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

    66 %hist is a command that is specific to IPython and not available in vannila 

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

    68 

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

    70 recent command. This implies that anything we type in is stored as history, 

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

    72 

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

    74 to =%hist= command. Hence

    75 ::

    76 

    77     %hist 5 

    78 

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

    80 The default number is 40.

    81 

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

    83 

    84 %% 1 %% Read through the %hist documenatation and find out how can we list all

    85         the commands between 5 and 10

    86 

    87 {{{ continue from paused state }}}

    88 

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

    90 ::

    91 

    92     %hist 5 10

    93 

    94 displays the commands from 5 to 10

    95 

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

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

    98 

    99 Before we do that, let us first look at history and identify what lines of code

   100 we require.Type

   101 ::

   102 

   103     %hist

   104 

   105 

   106 {{{ point to the lines }}}

   107 

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

   109 error. Hence we do not need seconf. The commands from third to sixth are 

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

   111 are setting the title correctly in the eigthth command.

   112 

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

   114 Hence the syntax of =%save= is

   115 ::

   116 

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

   118 

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

   120 

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

   122 the specified file.

   123 

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

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

   126 

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

   128 

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

   130 

   131 %% 2 %% change the label on y-axis to "y" and save the lines of code

   132         accordingly

   133 

   134 {{{ continue from paused state }}}

   135 

   136 we use the command =ylabel= on interpreter as

   137 ::

   138 

   139     ylabel("y")

   140 

   141 and then do

   142 ::

   143 

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

   145 

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

   147 the file as a python script.

   148 

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

   150 ::

   151 

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

   153 

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

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

   156 

   157 Hence on your terminal type

   158 ::

   159 

   160     show()

   161 

   162 to show the plot.

   163 

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

   165 

   166 %% 3 %% Use %hist and %save and create a script that has show in it and run it

   167         to produce and show the plot.

   168 

   169 {{{ continue from paused state }}}

   170 

   171 We first look at the history using

   172 ::

   173 

   174     %hist 20

   175 

   176 Then save the script using

   177 ::

   178 

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

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

   181 

   182 We get the desired plot.

   183 

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

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

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

   187 interpreter and used to run the script.

   188 

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

   190 

   191 %% 4 %% Run the script without using the -i option. Do you find any difference?

   192 

   193 {{{ continue from paused state }}}

   194 

   195 We see that it raises nameerror saying the name linspace is not found.

   196 

   197 {{{ Show summary slide }}}

   198 

   199 This brings us to the end of the tutorial.

   200 we have looked at 

   201 

   202  * Retreiving history using =%hist= command

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

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

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

   206 

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

   208 

   209 #[Nishanth]: Will add this line after all of us fix on one.

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

   211 

   212 Hope you have enjoyed and found it useful.

   213 Thankyou

   214