PoojaMoolya: Created page with "{| border=1 |'''Time''' |'''Narration''' |- |00:01 |Welcome to the spoken tutorial on '''Writing Python scripts.''' |- |00:06 |In this tutorial we will learn, What is '''im..."

2019-06-10T05:26:28Z

Created page with "{| border=1 |'''Time''' |'''Narration''' |- |00:01 |Welcome to the spoken tutorial on '''Writing Python scripts.''' |- |00:06 |In this tutorial we will learn, What is '''im..."

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{| border=1
|'''Time'''
|'''Narration'''

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|00:01
|Welcome to the spoken tutorial on '''Writing Python scripts.'''

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|00:06
|In this tutorial we will learn, What is '''importing''' ?

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|00:12
|Write your own '''Python modules''' and

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|00:15
|Understand the double underscore '''name''' double underscore double equal to within double quotes double underscore '''main double underscore idiom'''

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|00:25
|To record this tutorial, I am using

'''Ubuntu Linux 16.04''' operating system

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|00:34
| '''Python 3.4.3 '''

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|00:37
|'''IPython 5.1.0''' and '''Gedit text editor'''

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|00:44
|To practise this tutorial, you should know how to '''Run''' basic '''Python commands''' on the '''IPython console '''

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|00:53
|And Use '''Python modules.'''

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|00:56
|If not, see the relevant '''Python''' tutorials on this website.

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|01:02
|We can write '''Python modules''' to bundle '''functions.'''

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|01:07
|We can then make use of these '''functions''' by importing '''modules''' to other '''scripts.'''

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|01:14
|Let us first write a '''function''' and save it in a '''script.'''

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|01:19
|Open any '''text editor''' and type the below code.

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|01:24
|This '''Python module''' has a '''function''' to compute '''gcd''' of two numbers. Please take care of the indentation.

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|01:33
|We have included a '''text case''' in the '''script'''. This '''text case''' will check the '''GCD function''' everytime the '''script''' is run.

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|01:43
|Let us save the file as '''gcd''' underscore '''script.py''' in the current '''working directory.'''

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|01:50
|Open a new '''terminal'''. Type, '''ipython3''' and press '''Enter.'''

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|01:59
|From here onwards remember to press the '''Enter''' key after typing every '''command''' on the '''terminal.'''

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|02:06
|Now we will run the '''script'''. Type, percentage '''run gcd''' underscore '''script dot py'''

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|02:16
|We get an output which says '''“Everything is OK”'''.

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|02:21
|It means that the '''test case''' checking '''gcd''' inside brackets '''40''' comma '''12''' equals to '''4''' is passed.

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|02:30
|What if we want to use the '''gcd function''' in some other '''scripts'''?

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|02:35
|This is possible since every '''Python''' file can be used as a '''module.'''

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|02:41
|But first, we will understand what happens when we '''import''' a '''module.'''

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|02:47
| Type, '''import sys'''

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|02:51
|Now type '''sys.path'''

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|02:55
|We can see a list of locations. This indicates that '''Python''' searches for a '''module''' when it encounters an '''import statement.'''

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|03:05
|The '''standard modules''' are built into '''Python''' itself.

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|03:09
|Otherwise it is found in system locations like slash '''usr''' slash '''lib''' slash '''python3.4''' slash

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|03:20
|The first item in the '''list''' is an empty '''string.'''

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|03:24
|It means the current '''working directory''' is also searched.

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|03:29
|We can '''import''' a '''module''' present in the current '''working directory'''. Type, '''import gcd''' underscore '''script'''

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|03:39
|Since '''gcd''' underscore '''script dot py''' is in the current '''working directory, import''' will work directly.

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|03:48
|Type the '''print statement''' as shown here.

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|03:53
|We get the '''gcd''' of 187 and 391 as output, which is 17.

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|04:00
|We can also see the output '''“Everything is OK”''' that we added as '''test code. '''

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|04:07
|This is also executed when we imported '''gcd''' underscore '''script.'''

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|04:13
|The '''test code''' is added to check the '''gcd function.'''

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|04:18
|'''Test code''' should only be executed when we '''run''' the '''Python script''' independently.

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|04:24
|To execute the '''test code''' when the '''module''' is imported to other '''scripts''', we can use double underscore '''name''' double underscore '''variable.'''

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|04:34
|Hereafter I will call this as '''name variable'''.

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|04:38
|First, we shall look at how to use the '''variable''' and then understand how it works.

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|04:45
| Now we will add this '''variable''' in the '''script''' '''gcd''' underscore '''script dot py'''

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|04:52
|Type the following after '''return a statement'''

''' if''' double underscore '''name''' double underscore double equal to inside double quotes double underscore '''main''' double underscore colon

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|05:07
|Indent the code properly.

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|05:10
|Save the file.

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|05:12
|Let us '''run''' the '''code'''. Type, percentage '''run gcd''' underscore '''script.py'''

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|05:21
|We can see that the test is executed successfully and we get output as '''Everything is OK'''

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|05:28
|Now we will check the changes by '''importing''' the '''module. '''

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|05:33
|Type, '''import gcd_script'''

We didn’t see any changes.

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|05:41
|Note that, once a '''module''' is imported, it cannot be '''imported''' again in an existing '''IPython console.'''

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|05:49
|So we will exit the existing '''IPython console''' by typing '''exit.'''

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|05:56
|Open another '''terminal'''. Type '''ipython3'''.

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|06:04
|Now we will '''import gcd''' underscore '''script.py'''. Type,''' import gcd''' underscore '''script'''

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|06:14
|We can see that now the '''test code''' is not executed. '''Everything is OK''' is not displayed as output.

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|06:22
|The '''name variable''' is local to every '''module'''. It is equal to '''main''' only when the file is run as a '''script.'''

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|06:31
|Hence, all the '''code''' under the '''block, if name''' double equal to within double quotes '''main''' is executed only when the file is run as a '''Python script.'''

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|06:43
|Switch back to the '''terminal.'''

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|06:46
|Type the following '''code''' which checks whether two numbers are relatively prime.

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|06:54
|We have '''imported gcd function''' from '''gcd''' underscore '''script.'''

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|07:00
|And use it in our calculations without the '''test code''' being executed.

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|07:06
|Two numbers are relatively prime when their '''gcd''' is equal to one.

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|07:12
|So we get output as '''Yes, 11 and 3 are relatively prime.'''

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|07:18
|Every '''Python''' file can be''' run''' in two ways: As an independent stand-alone '''script ''' or

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|07:26
|As a '''Python module''' which can be imported by other '''Python scripts''' or '''modules.'''

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|07:33
|This brings us to the end of this tutorial. Let us summarize.

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|07:37
| In this tutorial, we have learnt to, '''Import a module.'''

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|07:44
| Use a '''script''' as a '''module '''

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|07:47
|Write '''test condition''' using the '''name variable''' and

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|07:52
|Restart '''IPython3''' if a changed '''module''' is to be imported again

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|07:57
|Here are some self assessment questions for you to solve

First. Which of the following '''variables''' contains the locations to search for '''Python modules'''

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|08:08
| Second. A '''module''' should contain only one '''function'''. True or False

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|08:14
|And the answers. First. '''sys.path''' contains the locations to search for '''Python modules.'''

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|08:22
|Second. '''False'''. A '''module''' can contain a wide range of '''functions.'''

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|08:28
|Please post your timed queries in this forum.

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|08:32
|Please post your general queries on Python in this forum.

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|08:37
|FOSSEE team coordinates the TBC project.

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|08:41
|Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India. For more details, visit this website.

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|08:51
|This is Priya from IIT Bombay signing off. Thanks for watching.

Python-3.4.3/C4/Writing-Python-Scripts/English-timed - Revision history

PoojaMoolya: Created page with "{| border=1 |'''Time''' |'''Narration''' |- |00:01 |Welcome to the spoken tutorial on '''Writing Python scripts.''' |- |00:06 |In this tutorial we will learn, What is '''im..."