Nancyvarkey at 12:50, 16 October 2018

2018-10-16T12:50:13Z

Priyacst: Created page with " {| style="border-spacing:0;" | style="background-color:#ffffff;border-top:0.5pt solid #000001;border-bottom:0.5pt solid #000001;border-left:0.5pt solid #000001;border-right:n..."

2018-10-04T10:48:01Z

Created page with " {| style="border-spacing:0;" | style="background-color:#ffffff;border-top:0.5pt solid #000001;border-bottom:0.5pt solid #000001;border-left:0.5pt solid #000001;border-right:n..."

New page

{| style="border-spacing:0;"
| style="background-color:#ffffff;border-top:0.5pt solid #000001;border-bottom:0.5pt solid #000001;border-left:0.5pt solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.095cm;padding-right:0.191cm;"| <center>Visual Cue </center>
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.095cm;padding-right:0.191cm;"| <center>Narration</center>

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.095cm;padding-right:0.191cm;"| Welcome to the spoken tutorial on '''Getting started with''' '''functions'''.

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Objectives

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.095cm;padding-right:0.191cm;"| In this tutorial, we will learn to,

* Define a '''function'''
* Define '''functions''' with '''arguments''' and
* use '''docstrings'''.

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System Specifications
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.095cm;padding-right:0.191cm;"| To record this tutorial, I am using

* '''Ubuntu Linux 16.04''' operating system
* '''Python 3.4.3 '''and
* '''IPython 5.1.0'''

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Pre-requisite

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.095cm;padding-right:0.191cm;"| To practise this tutorial, you should know how to use '''tuples.'''

If not, see the relevant '''Python''' tutorials on this website.

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'''Function'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.095cm;padding-right:0.191cm;"| First we will learn about functions.

* A '''function''' is a portion of '''code''' within a larger '''program''' that performs a specific task.
* '''Functions '''are useful in reusing the '''code''' and eliminate code redundancy.
* '''Functions''' are also used to organise our code into manageable blocks.

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Syntax of functions:

def function_name(parameters):"""docstring""" statement(s)

<nowiki>return [expression]</nowiki>

Highlight according to narration
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.095cm;padding-right:0.191cm;"| Here is the syntax for defining the functions.

'''def''' is the '''keyword '''which defines the function name.

colon is used to mark the end of the function name.

'''docstring''' is the documentation string to describe what the function does.

It is an optional, but recommended.

'''Statement''' makes the function body and it must have 4 indentation level.

'''return''' statement is to return a value from the function and it is also indented by 4 spaces.

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Example: Function

'''f(x)''' a mathematical '''function'''

'''def f(x):'''

'''return x*x'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.095cm;padding-right:0.191cm;"| Now we will understand the functions with an example.

Consider a mathematical '''function''' '''f''' ''of''''' x''''' is equal to'' '''x''' ''squared''.

Here '''x''' is a '''variable'''. '''f '''''of '''''x''' changes when '''x''' changes.

Let us define our '''function f '''''of '''''x.'''

The first line '''def f '''''of''''' x '''is used to define the '''function''' '''name''' and its '''parameters.'''

The second line uses the function parameters to return the required value.

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.095cm;padding-right:0.191cm;"| Let us start '''ipython.'''

Open the terminal.

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then press Enter
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.095cm;padding-right:0.191cm;"| Type '''ipython3 '''and press '''Enter'''.

From here onwards, remember to press the '''Enter''' key after typing every command on the terminal.

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'''def f(x):'''

'''return x*x'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.095cm;padding-right:0.191cm;"| Type,

'''def f '''''inside brackets '''''x '''''colon''

'''return x '''asterisk '''x'''

and press the '''Enter''' key two times.

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'''f(2)'''

'''f(2.5)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.095cm;padding-right:0.191cm;"| Let us call the '''f '''''of''' ''x '''with different '''arguments.'''

Type,

'''f '''''inside brackets '''''2'''

'''f '''''inside brackets '''''2.5'''

It returned 4 and 6.25 respectively.

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'''def greet():'''

'''print ("No function arguments")'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.095cm;padding-right:0.191cm;"| Now let us see how to write functions without arguments.

Type the code as shown.

It defines a new '''function''' named '''greet''' which will print '''"No function arguments"'''

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'''greet()'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.095cm;padding-right:0.191cm;"| Now we will call the '''function''' as,'''greet '''''open and close parentheses''

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.095cm;padding-right:0.191cm;"| Note that it is not mandatory for a '''function''' to '''return''' '''values'''.

The '''function greet''' neither takes any '''arguments''' nor '''returns''' any '''value'''.

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'''docstrings'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.095cm;padding-right:0.191cm;"| Next we will learn how to comment in a code.

Documenting/commenting code is a good practice.

'''Docstrings''' are triple quoted '''comments''' entered just after the '''function''' '''definition'''.

It implies what the '''function''' does.

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| style="background-color:#ffffff;border-top:0.5pt solid #000001;border-bottom:0.5pt solid #000001;border-left:0.5pt solid #000001;border-right:none;padding-top:0cm;padding-bottom:0cm;padding-left:0.095cm;padding-right:0.191cm;"| Type, (type manually)'''def avg(a, b):'''

'''""" avg takes two numbers as input a & b. Returns the average of a and b"""'''

'''return (a + b) / 2.0'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.095cm;padding-right:0.191cm;"| Let us write a '''function '''which '''returns average '''of two numbers.

Type the code as shown.

and press the '''Enter''' key two times.

Comments within triple quotes give a clear explanation about the code.

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'''avg?'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.095cm;padding-right:0.191cm;"| Type,

'''avg '''''question mark''''' '''

Here we can see the '''docstring '''of the '''function avg.'''

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'''avg(3, 5)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.095cm;padding-right:0.191cm;"| Now let us pass 3 and 5 as values to the arguments '''a''' and '''b''' to the function '''avg.'''

Type, '''avg '''''inside brackets''''' 3 '''''comma''''' 5'''

We get 4.0 as output.

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.095cm;padding-right:0.191cm;"| Pause the video.

Try this exercise and then resume the video.

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Assignment 1
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.095cm;padding-right:0.191cm;"| Write a '''function''' '''circle '''which returns the '''area''' and '''perimeter''' of a '''circle''' with given radius '''r'''.

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.095cm;padding-right:0.191cm;"| Switch back to the terminal for the solution.

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'''def circle(r):'''

'''"""returns area and perimeter of a circle '''

'''given radius r"""'''

'''pi = 3.14'''

'''area = pi * r * r'''

'''perimeter = 2 * pi * r return area, perimeter'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.095cm;padding-right:0.191cm;"| Type the code as shown.

Press the '''Enter''' key two times.

The '''circle '''function requires us to '''return''' two values.

A '''python''' '''function''' can return any number of values in the form of a tuple.

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'''a, p = circle(6)'''
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.095cm;padding-right:0.191cm;"| Let us call the '''function circle''' as,

'''a '''''comma''''' p '''''is equal to''''' circle '''''inside brackets '''''6'''

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'''print (a, p)'''

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.095cm;padding-right:0.191cm;"| Type,

'''print '''''inside brackets '''''a '''''comma''''' p'''

We can see the output as area and perimeter of a circle of radius 6.

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Summary

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.095cm;padding-right:0.191cm;"| This brings us to the end of this tutorial. Let us summarize.

In this tutorial, we have learnt to,

* Define '''functions''' in '''Python'''
* Call a '''function''' by specifying the '''function''' '''name'''
* Write '''docstrings''' to a '''function''' by putting it as a '''triple quoted string'''
* Pass '''parameters''' to a '''function'''
* Return '''values''' from a '''function'''.

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Self assessment questions
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.095cm;padding-right:0.191cm;"| Here are some self assessment questions for you to solve

# How many arguments can be passed to a Python function?

2. Write a '''function''' to find the area of a rectangle

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Solution of self assessment questions

| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.095cm;padding-right:0.191cm;"| And the answers,

# Any number of '''arguments''' can be passed to a '''Python''' '''function'''.

2. We can write a function to find the area of a rectangle as:

'''def rectangle''''' underscore '''''area '''''inside brackets '''''l '''''comma''''' b '''''colon''

'''return l '''''asterisk''''' b '''

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.095cm;padding-right:0.191cm;"| Please post your timed queries in this forum.

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.095cm;padding-right:0.191cm;"| Please post your general queries on Python in this forum.

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.095cm;padding-right:0.191cm;"| FOSSEE team coordinates the TBC project.

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Acknowledgment

http://spoken-tutorial.org
| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.095cm;padding-right:0.191cm;"| Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.

For more details, visit this website.

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| style="background-color:#ffffff;border:0.5pt solid #000001;padding-top:0cm;padding-bottom:0cm;padding-left:0.095cm;padding-right:0.191cm;"| This is Priya from IIT Bombay signing off.

Thanks for watching.

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Python-3.4.3/C4/Getting-Started-with-Functions/English - Revision history

Nancyvarkey at 12:50, 16 October 2018

Priyacst: Created page with " {| style="border-spacing:0;" | style="background-color:#ffffff;border-top:0.5pt solid #000001;border-bottom:0.5pt solid #000001;border-left:0.5pt solid #000001;border-right:n..."