Python/C4/Getting-started-with-functions/English-timed - Revision history

PoojaMoolya at 07:14, 27 March 2017

2017-03-27T07:14:37Z

PoojaMoolya at 11:04, 20 February 2017

2017-02-20T11:04:27Z

Gaurav at 10:20, 10 July 2014

2014-07-10T10:20:34Z

Gaurav at 10:20, 10 July 2014

2014-07-10T10:20:12Z

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Sneha at 06:07, 1 April 2013

2013-04-01T06:07:48Z

Sneha at 10:43, 28 March 2013

2013-03-28T10:43:07Z

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Minal: Created page with '{| border=1 !Visual Cue !Narration |- | 0:01 | Hello friends and welcome to the tutorial 'Getting started with functions'. |- | 0:05 | At the end of this tutorial, you will be …'

2013-01-02T12:13:55Z

Created page with '{| border=1 !Visual Cue !Narration |- | 0:01 | Hello friends and welcome to the tutorial 'Getting started with functions'. |- | 0:05 | At the end of this tutorial, you will be …'

New page

{| border=1
!Visual Cue
!Narration
|-
| 0:01
| Hello friends and welcome to the tutorial 'Getting started with functions'.

|-
| 0:05
| At the end of this tutorial, you will be able to,

# Define a function.
# Define functions with arguments.
# Learn about docstrings.
# Learn about function return value.
# Read code.

|-
| 0:16
| Before beginning this tutorial,we would suggest you to complete the tutorial on "Conditionals" and "Loops".

|-
| 0:22
| While writing code, we always want to reduce the number of lines of code, and functions is a way of reusing the code.

|-
| 0:32
| Thus the same lines of code can be used as many times as needed.

|-
| 0:35
| A function is a portion of code within a larger program that performs a specific task and is relatively independent of the remaining code.

|-
| 0:43
| Now let us get more familiar with functions,

|-
| 0:48
| Consider a mathematical function f of x = x square.

|-
| 0:53
| Here x is a variable and with different values of x the value of function will change.

|-
| 0:58
| When x is one, f(1) will return the value 1 and f(2) will return us the value 4.

|-
| 1:05
| Let us now see how to define the function f of x in python.

|-
| 1:10
| Start your ipython interpreter by typing,ipython in command line.

|-
| 1:17
| Let us define our function f of x

|-
|1:19
|So type def f within bracket x colon
return x star x

|-
|1:29
|Star denotes multipication

|-
| 1:34
| Well that defined the function, so before learning what we did let us see if it returns the expected values, try,

|-
|1:45
|f(1)
f(2)

|-
| 1:52
| Yes, it returned 1 and 4 respectively.

|-
| 1:55
| And now let us see what we did.

|-
| 1:58
| We wrote two lines: The first line <tt>def f of x </tt> is used to define the name and the parameters to the function, and the second line is used to fix what the function is supposed to return.

|-
| 2:12
| <tt>def</tt> is a keyword and <tt>f</tt> is the name of the function and <tt>x</tt> the parameter of the function.

|-
| 2:19
| Pause the video here, try out the following exercise and resume the video.

|-
| 2:24
| '''Write a python function named <tt>cube</tt> which computes the cube of''' a given number n.

|-
| 2:31
| Switch to your terminal for solution.

|-
| 2:33
| The problem can be solved as,

|-
|2:36
|In the terminal type def cube within bracket n colon
return n star star 3

|-
| 2:48
| Let us check whether our function returns the cube of a number or not

|-
|2:53
|So type cube within bracket 2 and hit enter.

|-
| 3:00
| It returned 8,which means we have defined our function,the right way.

|-
| 3:05
| And now let us see how to write functions without arguments.

|-
| 3:09
| let us define a new function called <tt>greet</tt> which will print <tt>Hello World</tt>.

|-
|3:15
|So type def greet() colon and hit enter.

|-
|3:26
|Then type print in double quotes Hello World exclamation

|-
| 3:39
| now we call the function as,greet() and hit enter.

|-
| 3:45
| Well that is a function which takes no arguments.

|-
| 3:49
| Also note that it is not mandatory for a function to return values.

|-
| 3:53
| The function <tt>greet</tt> neither takes any argument nor returns any value.

|-
| 3:57
| Now let us see how to write functions with more than one argument.

|-
| 4:03
| Pause the video here, try out the following exercise and resume the video.

|-
| 4:08
| Write a python function named <tt>avg</tt> which computes the average of <tt>a</tt> and <tt>b</tt>.

|-
| 4:16
| Switch to your terminal for solution.

|-
|4:19
|Type def avg within bracket a comma b colon
return within bracket a + b divided by 2

|-
|4:36
|For division we use slash.

|-
| 4:42
| Let us test our function,

|-
|4:44
|Type on terminal avg within bracket 20 comma 30 and hit enter.

|-
| 4:53
| We get the correct average, 25.

|-
| 4:56
| Thus if we want a function to accept more arguments, we just list them separated with a comma between the parenthesis after the function's name in the <tt>def</tt> line.

|-
| 5:06
| It is always a good practice to document the code that we write, and for a function we define, we should write an abstract of what the function does, and that is called a docstring.

|-
| 5:19
| Let us modify the function <tt>avg</tt> and add docstring to it.

|-
| 5:24
| Do the following,

|-
|5:25
|So now in the terminal type def avg within bracket a comma b colon

|-
|5:38
|Then in triple double quote you can type avg takes two numbers as input (a & b), and returns the average of a and b

|-
|5:50
|Then type return return within bracket a+b divided by 2

|-
|6:02
|Note that we have a syntax error.

|-
|6:09
|The error that we saw here is because of indentation error in return(a+b)/2

|-
|6:15
|So just input that command again.

|-
|6:25
|So type def avg within bracket a comma b colon

""" avg takes two numbers as input (a & b), and
returns the average of a and b"""
return within bracket a+b divided by 2

|-
| 6:45
| Note that docstrings are entered in the immediate line after the function definition and put as a triple quoted string.

|-
| 6:55
| And here as far as the code functionality is concerned, we didn't do anything.

|-
| 7:00
| We just added an abstract of what the function does.

|-
| 7:03
| Now try this in the ipython interpreter.

|-
|7:07
|Type avg and question mark.
|-
| 7:12
| It displays the docstring as we gave it.

|-
| 7:16
| Thus docstring is a good way of documenting the function we write.

|-
| 7:21
| Now type comma f question mark and hit enter.

|-
| 7:29
| It does have a docstring associated with it.

|-
|7:37
|Sorry It doesnot have a docstring associated with it.

|-
| 7:40
| Also we cannot infer anything from the function name, and thus we are forced to read the code to understand about the function.

|-
| 7:48
| Pause the video here, try out the following exercise and resume the video.

|-
| 7:54
| Add docstring to the function f.

|-
| 7:59
| We need to define the function again to add docstring to the function <tt>f</tt> and we do it as,

|-
| 8:06
| def f within bracket x colon

|-
| 8:13
| """Accepts a number x as argument and, returns the square of the number x."""

|-
| 8:24
| return x star x

|-
| 8:32
| Let us solve one more exercise

|-
| 8:34
| Pause the video here, try out the following exercise and resume the video.

|-
| 8:41
| '''Write a python function named <tt>circle</tt> which returns the''' area and perimeter of a circle given radius <tt>r</tt>.

|-
| 8:52
| Switch to the terminal for solution.

|-
| 8:57
| The problem requires us to return two values instead of one which we were doing till now.

|-
| 9:03
| We can solve the problem as,

|-
|9:05
|So now we can type in terminal
def circle within bracket r colon
"""returns area and perimeter of a circle given radius r"""
pi = 3.14
area = pi star r star r
perimeter = 2 star pi star r
return area comma perimeter and hit enter.

|-
| 10:04
| A python function can return any number of values.

|-
| 10:07
| There is no restriction for it.

|-
| 10:09
| Let us call the function <tt>circle</tt> as,

|-
|10:12
|Typing it on terminal a comma p = circle within bracket 6
print a
print p

|-
| 10:39
| Now we have done enough coding, let us do some code reading exercise,

|-
| 10:46
| Pause here and try to figure out what the function <tt>what</tt> does.

|-
| 10:54
| '''def what within bracket n colon'''

|-
| 10:58
| <nowiki>if n less than 0 colon n = -n while n greater than 0 colon</nowiki>

|-
| 11:08
| '''if n modulo 2 == 1 colon'''

|-
| 11:12
| return False

|-
| 11:14
| n slash = 10

|-
| 11:19
| And the next line is return True

|-
| 11:23
| continue from paused state It will return true if <tt>n modulo 2</tt> is not equal to 1 and will return false, otherwise.

|-
| 11:36
| The function here returns <tt>True</tt> if all the digits of the number <tt>n</tt> are even, otherwise it returns <tt>False</tt>.

|-
| 11:45
| Now one more code reading exercise,

|-
|11:51
|So it is given def even underscore digits within bracket n colon
"""returns True if all the digits in the number n are even, returns False if all the digits in the number n are not even"""

|-
|12:13
|Then next line if n less than 0 colon n = -n while n greater than 0 colon

|-
|12:24
|The next line if n modulo 2 == 1 colon
return False
n slash= 10
return True

|-
| 12:40
| Pause here and try to figure out what the function <tt>what</tt> does.

|-
| 12:48
| '''def what within bracket n colon'''

|-
| 12:52
| <nowiki>i = 1 while i star i les than n colon</nowiki>

|-
| 12:59
| i += 1

|-
| 13:02
| return i star i == n comma i

|-
| 13:07
| continue from paused state The function returns two values.

|-
| 13:11
| One it returns the result of the while statement whether true of false, and second it prints the value that ''ii`'' currently holds.

|-
| 13:23
| Here, the function returns <tt>True</tt> and the square root of <tt>n</tt> if n is a perfect square, otherwise it returns <tt>False</tt> and the square root of the next perfect square.

|-
|13:37
|So we look at that

|-
|13:40
|def is underscore perfect underscore square within bracket n colon
"""returns True and square root of n, if n is a perfect square, otherwise returns False and the square root of the next perfect square""" i = 1 while i star i less than n colon
i += 1
return i star i == n comma i

|-
| 14:14
| This brings us to the end of this tutorial.

|-
| 14:17
| In this tutorial, we have learnt to, 1. Define functions in Python by using the keyword <tt>def</tt>.

|-
| 14:22
| 2. Call the function by specifying the function name.

|-
| 14:25
| 3. Assign a docstring to a function by putting it as a triple quoted string.

|-
| 14:33
| 4. Pass parameters to a function.

|-
| 14:37
| 5. Return values from a function.

|-
| 14:39
| Here are some self assessment questions for you to solve

|-
| 14:42
| 1. What will the function do?

|-
| 14:46
| def what(x)

|-
| 14:48
| return x star x

|-
| 14:50
| Returns the square of x

|-
| 14:52
| Returns x

|-
| 14:54
| Function doesn't have docstring

|-
| 14:57
| Error

|-
| 14:59
| 1. How many arguments can be passed to a python function?
** None
** One
** Two
** Any

|-
| 15:07
| 1. Write a function which calculates the area of a rectangle.

|-
| 15:12
| And the answers,

|-
| 15:14
| 1.The function will result into an error due to the use of wrong syntax in defining the function.

|-
| 15:27
| The function line should always end with a colon

|-
| 15:32
| Any number of arguments can be passed to a python function.

|-
| 15:37
| As we know, area of a rectangle is product of it's length and breadth.

|-
| 15:41
| Hence, we define our function as,

|-
| 15:42
| def area within bracket l comma b colon

|-
| 15:47
| return l star b

|-
|15:51
| Hope you have enjoyed this tutorial and found it useful.

|-
| 15:55
| Thank you!

|}

@@ Line 206: / Line 206: @@
 |-
 | 05:24
-| Do the following,
+| Do the following,So now in the terminal type def avg within bracket a comma b colon
-−
-|-
-|05:25
-|So now in the terminal type def avg within bracket a comma b colon
 |-
@@ Line 538: / Line 534: @@
 |-
 | 15:41
-| Hence, we define our function as,
+| Hence, we define our function as, def area within bracket l comma b colon
-−
-|-
-| 15:42
-| def area within bracket l comma b colon
 |-

@@ Line 10: / Line 10: @@
 |  00:05
 | At the end of this tutorial, you will be able to,
 Define a function.
-# Define a function.
+Define functions with arguments.
-# Define functions with arguments.
+Learn about docstrings.
-# Learn about docstrings.
+Learn about function return value.
-# Learn about function return value.
+Read code.
-# Read code.
 |-
@@ Line 63: / Line 62: @@
 |-
 |01:19
-|So type def f within bracket x colon
+|So type def f within bracket x colon    return x star x
-         return x star x
 |-
@@ Line 76: / Line 74: @@
 |-
 |01:45
-|f(1)
+|f(1) f(2)
- f(2)
 |-
@@ Line 113: / Line 110: @@
 |-
 |02:36
-|In the terminal type def cube within bracket n colon
+|In the terminal type def cube within bracket n colon return n star star 3
-                      return n star star 3
 |-
@@ Line 178: / Line 174: @@
 |-
 |04:19
-|Type def avg within bracket a comma b colon
+|Type def avg within bracket a comma b colon return  within bracket a + b divided by 2
-      return  within bracket a + b divided by 2
 |-
@@ Line 239: / Line 234: @@
 |-
 |06:25
-|So type def avg within bracket a comma b colon
+|So type def avg within bracket a comma b colon  """ avg takes two numbers as input (a & b), and returns the average of a and b""" return  within bracket a+b divided by 2
-−
-  """ avg takes two numbers as input (a & b), and
 returns the average of a and b"""
 return  within bracket a+b divided by 2
 |-
@@ Line 339: / Line 330: @@
 |-
 |09:05
-|So now we can type in terminal
+|So now we can type in terminal  def circle within bracket r colon """returns area and perimeter of a circle given radius r"""
-  def circle within bracket r colon
+pi = 3.14
- """returns area and perimeter of a circle given radius r"""
+area = pi star r star r
- pi = 3.14
+perimeter = 2 star pi star r
- area = pi star r star r
+return area comma  perimeter and hit enter.
- perimeter = 2 star pi star r
- return area comma  perimeter and hit enter.
 |-
@@ Line 361: / Line 350: @@
 |-
 |10:12
-|Typing it on terminal a comma  p = circle within bracket 6
+|Typing it on terminal a comma  p = circle within bracket 6. print a, print p
-			print a
-			print p
 |-
@@ Line 411: / Line 398: @@
 |-
 |11:51
-|So it is given def even underscore digits within bracket n  colon
+|So it is given def even underscore digits within bracket n  colon """returns True if all the digits in the number n are even, returns False if all the digits in the number n are not even"""
 """returns True if all the digits in the number n are even, returns False if all the digits in the number n are not even"""
 |-
@@ Line 420: / Line 406: @@
 |-
 |12:24
-|The next line if n modulo 2 == 1 colon
+|The next line if n modulo 2 == 1 colon return False n slash= 10 return True
-		return False
-		n slash= 10
-		return True
 |-
@@ Line 463: / Line 446: @@
 |-
 |13:40
-|def is underscore perfect underscore square within bracket  n colon
+|def is underscore perfect underscore square within bracket  n colon """returns True and square root of n, if n is a perfect square, otherwise returns False and the square root of the next perfect square""" i = 1 while i star i less than n colon i += 1 return i star i == n comma  i
 """returns True and square root of n, if n is a perfect square, otherwise returns False and the square root of the next perfect square""" i = 1 while i star i less than n colon
 i += 1
 return i star i == n comma  i
 |-
@@ Line 474: / Line 454: @@
 |-
 | 14:17
-| In this tutorial, we have learnt to, 1. Define functions in Python by using the keyword def  .
+| In this tutorial, we have learnt to, Define functions in Python by using the keyword def  .
 |-
 | 14:22
-| 2. Call the function by specifying the function name.
+|  Call the function by specifying the function name.
 |-
 | 14:25
-| 3. Assign a doc string to a function by putting it as a triple quoted string.
+|  Assign a doc string to a function by putting it as a triple quoted string.
 |-
 | 14:33
-| 4. Pass parameters to a function.
+|  Pass parameters to a function.
 |-
 | 14:37
-| 5. Then  Return values from a function.
+| Then  Return values from a function.
 |-
@@ Line 498: / Line 478: @@
 |-
 | 14:42
-| 1. What will the function do?
+|  What will the function do?
 |-
@@ Line 526: / Line 506: @@
 |-
 | 14:59
-| 1. How many arguments can be passed to a python function?
+| How many arguments can be passed to a python function?
-** None
+None
-** One
+One
-** Two
+Two
-** Any
+Any
 |-
 | 15:07
-| 1. Write a function which calculates the area of a rectangle.
+| Write a function which calculates the area of a rectangle.
 |-
@@ Line 542: / Line 522: @@
 |-
 | 15:14
-| 1.The function will result into an error due to the use of wrong syntax in defining the function.
+| The function will result into an error due to the use of wrong syntax in defining the function.
 |-

@@ Line 96: / Line 96: @@
 |-
 | 2:19
-| Pause the video here, try out the following exercise and resume the video.
+| Pause the video here, try out the following exercise and resume.
 |-
@@ Line 141: / Line 141: @@
 |-
 |3:26
-|Then type print in double quotes Hello World exclamation
+|Then type print within double quotes Hello World exclamation
 |-
@@ Line 173: / Line 173: @@
 |-
 | 4:16
-| Switch to your terminal for solution.
+| Switch to  terminal for solution.
 |-
@@ Line 222: / Line 222: @@
 |-
 |5:50
-|Then type return return  within bracket a+b divided by 2
+|Then type return  within bracket a+b and hit enter
 |-
@@ Line 273: / Line 273: @@
 |-
 | 7:21
-| Now type comma f question mark and hit enter.
+| Now type f question mark and hit enter.
 |-
@@ Line 309: / Line 309: @@
 |-
 | 8:24
-|  return x star x
+| Then type  return x star x
 |-
@@ Line 317: / Line 317: @@
 |-
 | 8:34
-| Pause the video here, try out the following exercise and resume the video.
+| Pause the video here, try out the exercise and resume the video.
 |-
@@ Line 369: / Line 369: @@
 |-
 | 10:46
-| Pause here and try to figure out what the function  what  does.
+| Pause the video here and try to figure out what the function  what  does.
 |-
@@ Line 425: / Line 425: @@
 |-
 | 12:40
-| Pause here and try to figure out what the function  what  does.
+| Pause here and   figure out what the function  what  does.
 |-
@@ Line 433: / Line 433: @@
 |-
 | 12:52
-| i = 1 while i star i les than n colon
+| i = 1 while i star i is  less than n colon
 |-
@@ Line 445: / Line 445: @@
 |-
 | 13:07
-| continue from paused state The function returns two values.
+| continue  the video The function returns two values.
 |-
@@ Line 453: / Line 453: @@
 |-
 | 13:23
-| Here, the function returns True  and the square root of n  if n is a perfect square, otherwise it returns  False  and the square root of the next perfect square.
+| Here, the function  True returns  and the square root of n  if n is a perfect square, otherwise it returns  False  and the square root of the next perfect square.
 |-
@@ Line 488: / Line 488: @@
 |-
 | 14:37
-| 5. Return values from a function.
+| 5. Then  Return values from a function.
 |-
@@ Line 538: / Line 538: @@
 |-
 | 15:12
-| And the answers,
+|Now we look at the the answers,
 |-