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diff --git a/script2col.rst b/script2col.rst new file mode 100644 index 0000000..3e820d6 --- /dev/null +++ b/script2col.rst @@ -0,0 +1,267 @@ +.. Objectives +.. ---------- + +.. At the end of this tutorial, you will be able to + +.. 1. Execute python scripts from command line. +.. #. Use import in scripts. +.. #. Import scipy and pylab modules +.. #. Use python standard modules and 3rd party modules. + + +.. Prerequisites +.. ------------- + +.. 1. should have ``pylab`` installed. +.. #. using plot command interactively. +.. #. embellishing a plot. +.. #. saving plots. + +.. Author : Anoop Jacob Thomas <anoop@fossee.in> + Internal Reviewer : Puneeth + External Reviewer : + Language Reviewer : Bhanukiran + Checklist OK? : <11-11-2010, Anand, OK> [2010-10-05] + + +==================== +Using Python modules +==================== + + + ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| {{{ Show the first slide containing title, name of the production | Hello Friends and Welcome to the spoken tutorial on | +| team along with the logo of MHRD }}} | 'Using Python Modules'. | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| {{{ switch to objectives slide }}} | At the end of this tutorial, you will be able to , | +| | | +| | 1. Execute python scripts from command line. | +| | #. Use import in scripts. | +| | #. Import scipy and pylab modules. | +| | #. Use python standard modules and 3rd party modules. | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| {{{ Switch to the pre-requisite slide }}} | Before beginning this tutorial,we would suggest you to complete the | +| | tutorial on "Using plot interactively", "Embellishing a plot" and | +| | "Saving plots". | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| {{{ switch to next slide on running python scripts from | | +| command line }}} | | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| | Let us create a simple python script to print hello world. Open your | +| | text editor and type the following, | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| {{{ open the text editor and type the following }}} | | +| :: | | +| | | +| print "Hello world!" | | +| print | | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| {{{ save the script as hello.py }}} | Now save this script as ``hello.py``, | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| {{{ Open the terminal }}} | Start the ipython interpreter | +| :: | | +| | | +| ipython | | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| :: | In the previous tutorials,we have seen how to run a script using | +| | the IPython interpreter using ``%run`` | +| %run -i hello.py | | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| {{{ Close the terminal }}} | but this is not the correct way of running a python | +| | script. | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| {{{ open terminal and navigate to directory where hello.py was saved }}} | The correct method is to run it using the Python interpreter. Open the | +| | terminal and navigate to the directory where hello.py is, | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| :: | now run the Python script as, | +| | | +| python hello.py | | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| | It executed the script and we got the output ``Hello World!``. | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| {{{ switch to next slide }}} | The syntax is ``python space filename``. | +| {{{ highlight ``python filename`` syntax on slide while narrating }}} | | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| {{{ switch to next slide, four plot problem }}} | Now, we have a four plot problem where we have plotted four plots in a | +| | single figure. Let us run that script from command line. | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| {{{ open the four_plot.py file in text editor and show }}} | If you don't have the script, then make one with the following set of | +| {{{ Pause for some time and then continue }}} | commands | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| :: | Now let us run four_plot.py as a python script. | +| | | +| python four_plot.py | | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| | Oops! even though it was supposed to work, it didn't. It gave an error | +| | ``linspace()`` is not defined, which means that the function | +| | ``linspace()`` is not available in the current name-space. | +| | | +| | But if you try to run the same script using ``%run -i four_plot.py`` | +| | in your IPython interpreter started with the option ``-pylab`` it will | +| | work, because the ``-pylab`` option does some work for us by importing | +| | the required modules to our name-space when ipython interpreter | +| | starts. And thus we don't have to explicitly import modules. | +| | | +| | So now let us try to fix the problem and run the script in command | +| | line, | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| {{{ switch to next slide, fix ``linspace`` problem }}} | add this line as the first line in the script, | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| {{{ add the line as first line in four_plot.py and save }}} | | +| :: | | +| | | +| from scipy import * | | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| :: | Now let us run the script again, | +| | | +| python four_plot.py | | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| | Now it gave another error -- plot not defined, | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| {{{ switch to next slide, thank you slide }}} | let us edit the file again and add this line as the | +| | second line in our script and save it, | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| {{{ add the line as second line in four_plot.py and save }}} | | +| :: | | +| | | +| from pylab import * | | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| {{{ Switch to the terminal }}} | And now, run the script, | +| :: | | +| | | +| python four_plot.py | | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| | Yes! it worked. So what did we do? | +| | | +| | We actually imported the required modules using the keyword ``import``. | +| | It could also be done as by using, | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| {{{ switch to next slide, better way of fixing }}} | from scipy import linspace | +| {{{ highlight the required line while narrating }}} | | +| | instead of, | +| | | +| | from scipy import * | +| | | +| | So in practice it is always good to use function names instead of | +| | asterisk or star. If we use asterisk to import from a particular | +| | module then it will replace any existing functions with the same name | +| | in our name-space. | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| {{{ switch to next slide, Instead of ``*`` }}} | So let us modify four_plot.py as, | +| | Hence we delete the first two lines of our code which we had added | +| | and add these lines | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| {{{ Switch to script 'four_plot.py' }}} | | +| {{{ delete the first two lines and add the following }}} | | +| :: | | +| | | +| from scipy import linspace, pi, sin | | +| from pylab import plot, legend, annotate | | +| from pylab import xlim, ylim, title, show | | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| :: | Now let us try running the code again as, | +| | | +| python four_plot.py | | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| | It works! In this method we actually imported the functions to the | +| | current name-space.There is one more way of doing it. And that | +| | is, | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| {{{ switch to slide 'another fix' }}} | Notice that we use ``scipy.pi`` instead of just ``pi`` as in the | +| {{{ highlight the required line while narrating }}} | previous method, and the functions are called as ``pylab.plot()`` and | +| | ``pylab.annotate()`` and not as ``plot()`` and ``annotate()``. | +| | | +| | Pause the video here, try out the following exercise and resume the video. | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| {{{ Show slide with exercise 1 }}} | Write a script to plot a sine wave from minus two pi to two pi. | +| | <Pause> | +| | It can solved as, | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| {{{ open sine.py and show it }}} | The first line we import the required functions ``linspace()`` , | +| | ``sin()`` and constant ``pi`` from the module scipy. The second and | +| | third line we import the functions ``plot()``, ``legend()``, | +| | ``show()``, ``title()``, ``xlabel()`` and ``ylabel()``. And the rest | +| | the code to generate the plot. | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| {{{ Pause for sometime and then continue }}} | | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| {{{ Switch to the terminal }}} | We can run it as, | +| :: | | +| | | +| python sine.py | | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| | As we can see, we our sine plot.Let us move further in our topic. | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| {{{ switch to next slide, What is a module? }}} | Until now we have been learning about importing modules, now what is a | +| | module? | +| | | +| | A module is simply a file containing Python definitions and | +| | statements. Definitions from a module can be imported into other | +| | modules or into the main module. | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| {{{ switch to next slide, Python standard library }}} | Python has a very rich standard library of modules. It is very | +| | extensive, offering a wide range of facilities. Some of the standard | +| | modules are, | +| | | +| | for Math: math, random | +| | for Internet access: urllib2, smtplib | +| | for System, Command line arguments: sys | +| | for Operating system interface: os | +| | for regular expressions: re | +| | for compression: gzip, zipfile, tarfile | +| | And there are lot more. | +| | | +| | Find more information at Python Library reference, | +| | ``http://docs.python.org/library/`` | +| | | +| | There are a lot of other modules like pylab, scipy, Mayavi, etc which | +| | are not part of the standard python library. | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| {{{ switch to next slide, summary }}} | This brings us to the end of this tutorial. In this tutorial, we have | +| | learnt to, | +| | | +| | 1. Run scripts from command line, | +| | #. Import modules by specifying the module name followed by | +| | an asterisk. | +| | #. Import only the required functions from modules by specifying | +| | the function name. | +| | #. Use python standard library. | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| {{{Show self assessment questions slide}}} | Here are some self assessment questions for you to solve | +| | | +| | 1. Which among this is correct ? | +| | | +| | - from scipy import plot | +| | - from numpy import plot | +| | - from matplotlib import plot | +| | - from pylab import plot | +| | | +| | 2. Which among these libraries is part of python standard library ? | +| | | +| | - Mayavi | +| | - scipy | +| | - matplotlib | +| | - urllib2 | +| | | +| | 3. Functions ``xlim()`` and ``ylim()`` can be imported to the current | +| | name-space as, | +| | | +| | - from pylab import xlim, ylim | +| | - import pylab | +| | - from scipy import xlim, ylim | +| | - import scipy | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| {{{solution of self assessment questions on slide}}} | And the answers, | +| | | +| | 1. The option ``from pylab import plot`` is the correct one, since plot | +| | is a function of module module. | +| | | +| | 2. ``urllib2`` is a part of the python standard library. | +| | | +| | 3. Functions ``xlim()`` and ``ylim()`` can be imported to the current | +| | name-space as, ``from pylab import xlim, ylim``. | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ +| | Hope you have enjoyed this tutorial and found it useful. | +| | Thank you! | ++----------------------------------------------------------------------------------+----------------------------------------------------------------------------------+ |