1 .. Objectives

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

     3 

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

     5    B - 

     6    C - 

     7    D - 

     8 

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

    10 

    11 .. #. Retrieve your ipython history 

    12 .. #. View a part of the history 

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

    14 .. #. Run a script from within ipython 

    15 

    16 

    17 .. Prerequisites

    18 .. -------------

    19 

    20 ..   1. Embellishing Plots

    21      

    22 .. Author              : Nishanth Amuluru

    23    Internal Reviewer   : 

    24    External Reviewer   :

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

    26 

    27 Script

    28 ------

    29 

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

    31 

    32 {{{ Show the slide containing title }}}

    33 

    34 {{{ Show the slide containing the outline slide }}}

    35 

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

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

    38 into a file and run it.

    39 

    40 Let us start ipython with pylab loaded, by typing

    41 ::

    42 

    43     $ ipython -pylab

    44 

    45 on the terminal

    46 

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

    48 

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

    50 ::

    51 

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

    53     plot(x, xsinx(x))

    54 

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

    56 ::

    57 

    58     plot(x, x*sin(x))

    59     plot(x, sin(x))

    60     xlabel("x")

    61     ylabel("$f(x)$")   

    62     title("x and xsin")

    63 

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

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

    66 ::

    67 

    68     %hist

    69 

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

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

    72 

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

    74 %hist is a command that is specific to IPython and not available in vannila 

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

    76 

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

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

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

    80 

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

    82 to =%hist= command. Hence

    83 ::

    84 

    85     %hist 5 

    86 

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

    88 The default number is 40.

    89 

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

    91 

    92 %% 1 %% Read through the documentation of %hist and find out how to

    93         list all the commands between 5 and 10

    94 

    95 {{{ continue from paused state }}}

    96 

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

    98 ::

    99 

   100     %hist 5 10

   101 

   102 displays the commands from 5 to 10

   103 

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

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

   106 

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

   108 we require.Type

   109 ::

   110 

   111     %hist

   112 

   113 

   114 {{{ point to the lines }}}

   115 

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

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

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

   119 are setting the title correctly in the eigthth command.

   120 

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

   122 Hence the syntax of =%save= is

   123 ::

   124 

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

   126 

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

   128 

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

   130 the specified file.

   131 

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

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

   134 

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

   136 

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

   138 

   139 %% 2 %% Change the label on y-axis to "y" and save the lines of code

   140         accordingly

   141 

   142 {{{ continue from paused state }}}

   143 

   144 we use the command =ylabel= on interpreter as

   145 ::

   146 

   147     ylabel("y")

   148 

   149 and then do

   150 ::

   151 

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

   153 

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

   155 the file as a python script.

   156 

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

   158 ::

   159 

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

   161 

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

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

   164 

   165 Hence on your terminal type

   166 ::

   167 

   168     show()

   169 

   170 to show the plot.

   171 

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

   173 

   174 %% 3 %% Use %hist and %save and create a script that has show in it and run it

   175         to produce and show the plot.

   176 

   177 {{{ continue from paused state }}}

   178 

   179 We first look at the history using

   180 ::

   181 

   182     %hist 20

   183 

   184 Then save the script using

   185 ::

   186 

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

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

   189 

   190 We get the desired plot.

   191 

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

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

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

   195 interpreter and used to run the script.

   196 

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

   198 

   199 %% 4 %% Run the script without using the -i option. Do you find any difference?

   200 

   201 {{{ continue from paused state }}}

   202 

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

   204 

   205 {{{ Show summary slide }}}

   206 

   207 This brings us to the end of the tutorial.

   208 we have looked at 

   209 

   210  * Retreiving history using =%hist= command

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

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

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

   214 

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

   216 

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

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

   219 

   220 Hope you have enjoyed and found it useful.

   221 Thank you!

   222