1 .. Author              : Nishanth

     2    Internal Reviewer 1 : 

     3    Internal Reviewer 2 : 

     4    External Reviewer   :

     5 

     6 .. Prerequisites: Embellinshing plots

     7 

     8 Script

     9 ======

    10 

    11 

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

    13 

    14 {{{ Show the slide containing title }}}

    15 

    16 {{{ Show the slide containing the outline slide }}}

    17 

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

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

    20 into a file and run it.

    21 

    22 Let us start ipython with pylab loaded, by typing

    23 ::

    24 

    25     $ ipython -pylab

    26 

    27 on the terminal

    28 

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

    30 

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

    32 ::

    33 

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

    35     plot(x, xsinx(x))

    36 

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

    38 ::

    39 

    40     plot(x, x*sin(x))

    41     plot(x, sin(x))

    42     xlabel("x")

    43     ylabel("$f(x)$")   

    44     title("x and xsin")

    45 

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

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

    48 ::

    49 

    50     %hist

    51 

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

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

    54 

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

    56 %hist is a command that is specific to IPython and not available in vannila 

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

    58 

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

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

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

    62 

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

    64 to =%hist= command. Hence

    65 ::

    66 

    67     %hist 5 

    68 

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

    70 The default number is 40.

    71 

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

    73 

    74 %% 1 %% Read through the %hist documenatation and find out how can we list all

    75         the commands between 5 and 10

    76 

    77 {{{ continue from paused state }}}

    78 

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

    80 ::

    81 

    82     %hist 5 10

    83 

    84 displays the commands from 5 to 10

    85 

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

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

    88 

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

    90 we require.Type

    91 ::

    92 

    93     %hist

    94 

    95 

    96 {{{ point to the lines }}}

    97 

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

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

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

   101 are setting the title correctly in the eigthth command.

   102 

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

   104 Hence the syntax of =%save= is

   105 ::

   106 

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

   108 

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

   110 

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

   112 the specified file.

   113 

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

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

   116 

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

   118 

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

   120 

   121 %% 2 %% change the label on y-axis to "y" and save the lines of code

   122         accordingly

   123 

   124 {{{ continue from paused state }}}

   125 

   126 we use the command =ylabel= on interpreter as

   127 ::

   128 

   129     ylabel("y")

   130 

   131 and then do

   132 ::

   133 

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

   135 

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

   137 the file as a python script.

   138 

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

   140 ::

   141 

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

   143 

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

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

   146 

   147 Hence on your terminal type

   148 ::

   149 

   150     show()

   151 

   152 to show the plot.

   153 

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

   155 

   156 %% 3 %% Use %hist and %save and create a script that has show in it and run it

   157         to produce and show the plot.

   158 

   159 {{{ continue from paused state }}}

   160 

   161 We first look at the history using

   162 ::

   163 

   164     %hist 20

   165 

   166 Then save the script using

   167 ::

   168 

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

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

   171 

   172 We get the desired plot.

   173 

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

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

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

   177 interpreter and used to run the script.

   178 

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

   180 

   181 %% 4 %% Run the script without using the -i option. Do you find any difference?

   182 

   183 {{{ continue from paused state }}}

   184 

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

   186 

   187 {{{ Show summary slide }}}

   188 

   189 This brings us to the end of the tutorial.

   190 we have looked at 

   191 

   192  * Retreiving history using =%hist= command

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

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

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

   196 

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

   198 

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

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

   201 

   202 Hope you have enjoyed and found it useful.

   203 Thankyou

   204  

   205 Questions

   206 =========

   207 

   208  1. How do you retrieve the recent 5 commands

   209 

   210     a. ``%hist``

   211     #. ``%hist -5``

   212     #. ``%hist 5``

   213     #. ``%hist 5-10``

   214 

   215     Answer: ``%hist 5``

   216     

   217  2. If there were 20 commands typed and ``%hist`` is used. How many commands 

   218     will be displayed.

   219 

   220     a. 10

   221     #. 20

   222     #. 21

   223     #. 19

   224 

   225     Answer: 21

   226 

   227  3. is ``%hist`` considered as a command

   228 

   229     a. True

   230     #. False

   231 

   232     Answer: True

   233 

   234  4. how do you retreive the commands from 20 to 50 (inclusive of 20 and 50)

   235 

   236     a. ``%hist 20 50``

   237     #. ``%hist 19 50``

   238     #. ``%hist 19 51``

   239     #. ``%hist 21 50``

   240 

   241     Answer: ``%hist 20 50``

   242 

   243  5. What does the ``%hist 2 5 7`` command do

   244 

   245     a. lists the second, fifth and seventh commands

   246     #. lists the commands from 2 to 5 and the seventh command

   247     #. raises an error

   248     #. lists the commands 2 to 7

   249 

   250     Answer: raises an error

   251 

   252  6. How many commands are displayed when lot of coomands were typed and 

   253     ``%hist`` is used.

   254 

   255     a. 20

   256     #. 10

   257     #. 50

   258     #. 40

   259 

   260     Answer: 40

   261 

   262  7. How do you save the lines 2 3 4 5 7 9 10 11

   263 

   264     a. ``%save filepath 2-5 7 9-11``

   265     #. ``%save filepath 2-11``

   266     #. ``%save filepath``

   267     #. ``%save 2-5 7 9 10 11``

   268 

   269     Answer: ``%save filepath 2-5 7 9-11``

   270 

   271  8. You are working in /home/user. Where is the file saved when you do

   272     ``%save hello.py 1-3`` 

   273 

   274     a. /home/user/hello.py

   275     #. /hello.py

   276     #. /home/hello.py

   277     #. /home/user/ipython/hello.py

   278 

   279     Answer: /home/user/hello.py

   280 

   281  9. Which lines are saved by the command ``%save filepath 2-5 7 1`` and in

   282     which order

   283 

   284     a. 2 3 4 5 7 1

   285     #. 1 2 3 4 5 6 7

   286     #. 2 5 7 1

   287     #. 1 2 5 7

   288 

   289  10. What happens when ``%save filepath line_numbers`` is used and a file

   290      already exists in that path.

   291 

   292     a. It is overwritten

   293     #. The commands are added to the file

   294     #. It raises an error

   295     #. A prompt to confirm overwriting is displayed 

   296 

   297     Answer: A prompt to confirm overwriting is displayed 

   298 

   299  11. Read through the documentation of ``%hist`` and find its alternative name

   300 

   301     Answer: ``%history``

   302 

   303  12. Are ``%run /home/user/saved.py`` and ``%run /home/user/saved`` the same

   304 

   305    a. Yes

   306    #. No

   307 

   308    Answer: Yes

   309 

   310  13. The file hello.py contains only one command ``x = x + 1``. What happens

   311      when you do ``%run hello.py``

   312 

   313     Answer: Raises a nameerror

   314 

   315   14. The file hello.py contains only one command ``x = x + 1``. If value of x

   316       is 5 and what does ``%run -i hello.py`` do.

   317 

   318     a. raises an error

   319     #. increments value of x by 1

   320     #. Does nothing

   321     

   322     Answer: increments the value of x by 1