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| author | Puneeth Chaganti | 2010-12-01 16:51:35 +0530 |
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| committer | Puneeth Chaganti | 2010-12-01 16:51:35 +0530 |
| commit | f3a34dfb4e879f3eb7274704f44546aac4add88f (patch) | |
| tree | 1cb0a8cc5dbd5ee2b374350915ed2addfa0fb447 /using python modules/script.rst | |
| parent | 347866ed0d29db61ee062563b1e1616cfb85588c (diff) | |
| download | st-scripts-f3a34dfb4e879f3eb7274704f44546aac4add88f.tar.gz st-scripts-f3a34dfb4e879f3eb7274704f44546aac4add88f.tar.bz2 st-scripts-f3a34dfb4e879f3eb7274704f44546aac4add88f.zip | |
Renamed all LOs to match with their names in progress.org.
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| -rw-r--r-- | using python modules/script.rst | 247 |
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diff --git a/using python modules/script.rst b/using python modules/script.rst deleted file mode 100644 index 0b0858b..0000000 --- a/using python modules/script.rst +++ /dev/null @@ -1,247 +0,0 @@ -.. 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 welcome slide }}} - -Welcome to the spoken tutorial on Using Python Modules. - -{{{ switch to next slide, outline slide }}} - -In this tutorial, we will see how to run python scripts from command -line. We'll see how to import modules, importing scipy and pylab -modules and have a look at the Python standard library. - -{{{ switch to next slide on executing 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 - -and save the script as ``hello.py``, - -{{{ save the script as hello.py }}} - -Till now we saw how to run a script using the IPython interpreter -using the -:: - - %run -i hello.py - -option, but that is not the correct way of running a python -script. - -The correct method is to run it using the Python interpreter. Open the -terminal and navigate to the directory where hello.py is, - -{{{ open terminal and navigate to directory where hello.py was saved }}} - -{{{ switch to next slide }}} - -now run the Python script as, -:: - - python hello.py - -It executed the script and we got the output ``Hello World!``. - -{{{ highlight ``python filename`` syntax on slide while narrating }}} - -The syntax is python space filename. - -{{{ switch to next slide, four plot problem }}} - -Now recall the four plot problem where we plotted four plots in a single -figure. Let us run that script from command line. - -If you don't have the script, - -{{{ open the four_plot.py file in text editor }}} - -just pause here and create a python script with the following lines -and save it as four_plot.py. - -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 the following 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, let us edit the file -again and add the line below the line we just added, - -{{{ switch to next slide, fix ``plot`` problem }}} - -{{{ add the line as second line in four_plot.py and save }}} -:: - - from pylab import * - -And 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 have also be done as, - -{{{ switch to next slide, better way of fixing }}} - -{{{ highlight the following in slide and say it loud }}} -:: - - from scipy import linspace - -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, -{{{ 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, and there is another method of doing it. And that -is, - -{{{ switch to next slide }}} - -Notice that we use ``scipy.pi`` instead of just ``pi`` as in the -previous method, and the functions are called as ``pylab.plot()`` and -``pylab.annotate()`` and not as ``plot()`` and ``annotate()``. - -{{{ switch to next slide, problem statement }}} - -%% %% Write a script to plot a sine wave from minus two pi to two pi. - -Pause here and try to solve the problem yourself before looking at the -solution. - -It can solved as, - -{{{ open sine.py and show it }}} - -the first line we import the required functions ``linspace()`` and -``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. - -We can run it as, -{{{ now switch focus to terminal and run the script }}} -:: - - python sine.py - -{{{ 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 -learned running scripts from command line, learned about modules, saw -the python standard library. - -{{{ switch to next slide, thank you slide }}} - -Thank you! |