Difference between revisions of "Python/C3/Getting-started-with-arrays/English-timed"
From Script | Spoken-Tutorial
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| − | + | |'''Time''' | |
| − | + | |'''Narration''' | |
| + | |||
|- | |- | ||
| − | | | + | | 00:01 |
| Hello friends and welcome to the spoken tutorial on 'Getting started with arrays'. | | Hello friends and welcome to the spoken tutorial on 'Getting started with arrays'. | ||
|- | |- | ||
| − | | | + | | 00:06 |
| At the end of this tutorial, you will be able to, | | At the end of this tutorial, you will be able to, | ||
| Line 17: | Line 18: | ||
|- | |- | ||
| − | | | + | | 00:26 |
| So Before beginning this tutorial,we would suggest you to complete the tutorial on "Getting started with Lists". | | So Before beginning this tutorial,we would suggest you to complete the tutorial on "Getting started with Lists". | ||
|- | |- | ||
| − | | | + | | 00:35 |
| Arrays are homogeneous data structures. | | Arrays are homogeneous data structures. | ||
| Line 29: | Line 30: | ||
|- | |- | ||
| − | | | + | | 00:45 |
|They can have only one type of data as their entries, be them all integers, strings, or maybe floats, but not a mix. | |They can have only one type of data as their entries, be them all integers, strings, or maybe floats, but not a mix. | ||
|- | |- | ||
| − | | | + | | 00:55 |
|Arrays of a given length are comparatively much faster in mathematical operations than lists of the same length, because of the fact that they are homogeneous data structures. | |Arrays of a given length are comparatively much faster in mathematical operations than lists of the same length, because of the fact that they are homogeneous data structures. | ||
|- | |- | ||
| − | | | + | |01:07 |
|Let us see how to create arrays. | |Let us see how to create arrays. | ||
|- | |- | ||
| − | | | + | | 01:11 |
| Run your IPython interpreter with space hypen pylab option, to load the required modules to work with arrays. | | Run your IPython interpreter with space hypen pylab option, to load the required modules to work with arrays. | ||
|- | |- | ||
| − | | | + | |01:21 |
|So type ipython space hypen pylab | |So type ipython space hypen pylab | ||
|- | |- | ||
| − | | | + | | 01:28 |
| To create an array we will use the function array() as,a1 = array within brackets square brackets 1 comma 2 comma 3 comma 4 | | To create an array we will use the function array() as,a1 = array within brackets square brackets 1 comma 2 comma 3 comma 4 | ||
|- | |- | ||
| − | | | + | | 01:45 |
| Notice that we created a one dimensional array here. | | Notice that we created a one dimensional array here. | ||
|- | |- | ||
| − | | | + | | 01:49 |
| Also notice that the object we passed to create an array is a list. | | Also notice that the object we passed to create an array is a list. | ||
|- | |- | ||
| − | | | + | | 01:54 |
|Now let us see how to create a two dimensional array. | |Now let us see how to create a two dimensional array. | ||
|- | |- | ||
| − | | | + | | 01:58 |
|We create two dimensional array by converting a list of lists to an array as, | |We create two dimensional array by converting a list of lists to an array as, | ||
a2 = array within brackets within square brackets 1 comma 2 comma 3 comma 4 comma then again within square brackets 5 comma 6 comma 7 comma 8 and hit enter. | a2 = array within brackets within square brackets 1 comma 2 comma 3 comma 4 comma then again within square brackets 5 comma 6 comma 7 comma 8 and hit enter. | ||
|- | |- | ||
| − | | | + | | 02:38 |
| Now let us use arrange() function to create the same array as before. | | Now let us use arrange() function to create the same array as before. | ||
|- | |- | ||
| − | | | + | |02:45 |
|For that type ar = arrange within bracket 1 comma 9 and hit enter,so type | |For that type ar = arrange within bracket 1 comma 9 and hit enter,so type | ||
print ar to get the output. | print ar to get the output. | ||
|- | |- | ||
| − | | | + | | 03:02 |
| So now, As you can see, we obtained a one dimensional array with elements from 1 to 8. | | So now, As you can see, we obtained a one dimensional array with elements from 1 to 8. | ||
|- | |- | ||
| − | | | + | | 03:12 |
|Now can we make it a two dimensional array of order 2 by 4? Yes,we can. | |Now can we make it a two dimensional array of order 2 by 4? Yes,we can. | ||
|- | |- | ||
| − | | | + | | 03:20 |
|For this we will have to use the function reshape() , | |For this we will have to use the function reshape() , | ||
|- | |- | ||
| − | | | + | |03:24 |
|So type ar.reshape brackets 2 comma 4 and hit enter | |So type ar.reshape brackets 2 comma 4 and hit enter | ||
|- | |- | ||
| − | | | + | |03:33 |
|So type ar.reshape within brackets 4 comma 2 | |So type ar.reshape within brackets 4 comma 2 | ||
then ar = ar dot reshape within brackets 2,4 | then ar = ar dot reshape within brackets 2,4 | ||
|- | |- | ||
| − | | | + | | 03:55 |
| Hence,we got our two-dimensional array. | | Hence,we got our two-dimensional array. | ||
|- | |- | ||
| − | | | + | | 03:58 |
|Now, let us see how to convert a list object to an array. | |Now, let us see how to convert a list object to an array. | ||
|- | |- | ||
| − | | | + | | 04:02 |
|We define a list,say l1 | |We define a list,say l1 | ||
|- | |- | ||
| − | | | + | |04:07 |
|So type l1 = within square brackets 1 comma 2 comma 3 comma 4 and hit enter | |So type l1 = within square brackets 1 comma 2 comma 3 comma 4 and hit enter | ||
|- | |- | ||
| − | | | + | | 04:16 |
| Now to convert this list to an array,we use the array function as, a3 = array within brackets l1 | | Now to convert this list to an array,we use the array function as, a3 = array within brackets l1 | ||
|- | |- | ||
| − | | | + | | 04:30 |
| To find the shape of an array we can use the method dot shape , | | To find the shape of an array we can use the method dot shape , | ||
|- | |- | ||
| − | | | + | | 04:36 |
|let us check the shape of the arrays we have created so far, | |let us check the shape of the arrays we have created so far, | ||
|- | |- | ||
| − | | | + | | 04:44 |
| a2 dot shape object is a tuple, and it returned a tuple (2 comma 4). | | a2 dot shape object is a tuple, and it returned a tuple (2 comma 4). | ||
|- | |- | ||
| − | | | + | | 04:52 |
|A tuple is nothing but an ordered list of elements. | |A tuple is nothing but an ordered list of elements. | ||
|- | |- | ||
| − | | | + | | 04:56 |
|So Pause the video here, try out the following exercise and resume the video. | |So Pause the video here, try out the following exercise and resume the video. | ||
|- | |- | ||
| − | | | + | | 05:12 |
| Find out the shape of the other arrays i.e. a1 comma a3 comma ar that we have created. | | Find out the shape of the other arrays i.e. a1 comma a3 comma ar that we have created. | ||
|- | |- | ||
| − | | | + | |05:22 |
|It can be done as | |It can be done as | ||
a1 dot shape | a1 dot shape | ||
| Line 151: | Line 152: | ||
|- | |- | ||
| − | | | + | | 05:37 |
| Now let us try to create a new array with a mix of elements and see what will happen, | | Now let us try to create a new array with a mix of elements and see what will happen, | ||
|- | |- | ||
| − | | | + | |05:45 |
|So type a4 = array within brackets then square bracket 1 comma 2 comma 3 comma and single quote a string and hit enter | |So type a4 = array within brackets then square bracket 1 comma 2 comma 3 comma and single quote a string and hit enter | ||
|- | |- | ||
| − | | | + | | 06:07 |
| Well, we would expect an error as it has been previously mentioned that arrays handle elements with the same data type, but it didn't raise an error. | | Well, we would expect an error as it has been previously mentioned that arrays handle elements with the same data type, but it didn't raise an error. | ||
|- | |- | ||
| − | | | + | | 06:16 |
|Let us check the values in the new array created. | |Let us check the values in the new array created. | ||
|- | |- | ||
| − | | | + | | 06:19 |
|So Type a4 in the terminal, | |So Type a4 in the terminal, | ||
|- | |- | ||
| − | | | + | | 06:27 |
| Did you notice it, all the elements have been implicitly type casted as strings, though our first three elements were meant to be integers. | | Did you notice it, all the elements have been implicitly type casted as strings, though our first three elements were meant to be integers. | ||
|- | |- | ||
| − | | | + | |06:37 |
| Also,if you have noticed,we got something like 'dtype S8' in the output. | | Also,if you have noticed,we got something like 'dtype S8' in the output. | ||
|- | |- | ||
| − | | | + | | 06:44 |
| dtype is nothing but the data type which is the minimum type required to hold the objects in the sequence. | | dtype is nothing but the data type which is the minimum type required to hold the objects in the sequence. | ||
|- | |- | ||
| − | | | + | | 06:52 |
| Let us now move on to study functions like zeros() function and ones() function. | | Let us now move on to study functions like zeros() function and ones() function. | ||
|- | |- | ||
| − | | | + | |06:59 |
|For this ,we will have to create a matrix. | |For this ,we will have to create a matrix. | ||
|- | |- | ||
| − | | | + | |07:02 |
|let us see how to create an identity matrix of a given size, this is a two-dimensional array in which all the diagonal elements are ones and rest of the elements are zeros. | |let us see how to create an identity matrix of a given size, this is a two-dimensional array in which all the diagonal elements are ones and rest of the elements are zeros. | ||
|- | |- | ||
| − | | | + | | 07:13 |
|We can create an identity matrix using the function identity() . | |We can create an identity matrix using the function identity() . | ||
|- | |- | ||
| − | | | + | | 07:18 |
|The function identity() takes an integer argument which specifies the size of the desired matrix, | |The function identity() takes an integer argument which specifies the size of the desired matrix, | ||
|- | |- | ||
| − | | | + | | 07:27 |
| As you can see the identity function returned a three by three square matrix with all the diagonal elements as one and the rest of the elements as zeros. | | As you can see the identity function returned a three by three square matrix with all the diagonal elements as one and the rest of the elements as zeros. | ||
|- | |- | ||
| − | | | + | |07:43 |
|So type identity within brackets 3 | |So type identity within brackets 3 | ||
|- | |- | ||
| − | | | + | | 07:48 |
| zeros() function accepts a tuple, which is the order of the array that we want to create, and it generates an array with all elements as zeros. | | zeros() function accepts a tuple, which is the order of the array that we want to create, and it generates an array with all elements as zeros. | ||
|- | |- | ||
| − | | | + | | 07:59 |
|Let us create an array of the order four by five with all the elements zero. | |Let us create an array of the order four by five with all the elements zero. | ||
|- | |- | ||
| − | | | + | |08:06 |
| We can do it using the method zeros(), | | We can do it using the method zeros(), | ||
|- | |- | ||
| − | | | + | |08:10 |
|So type zeros within brackets then again in bracket 4 comma 5 and hit enter | |So type zeros within brackets then again in bracket 4 comma 5 and hit enter | ||
|- | |- | ||
| − | | | + | | 08:21 |
| Notice that we passed a tuple to the function zeros. | | Notice that we passed a tuple to the function zeros. | ||
|- | |- | ||
| − | | | + | | 08:25 |
|Pause the video here, try out the following exercise and resume the video. | |Pause the video here, try out the following exercise and resume the video. | ||
|- | |- | ||
| − | | | + | |08:33 |
|So now we learnt two functions identity and zeros | |So now we learnt two functions identity and zeros | ||
|- | |- | ||
| − | | | + | | 08:38 |
| '''Find out about the functions''' | | '''Find out about the functions''' | ||
|- | |- | ||
| − | | | + | | 08:41 |
| zeros underscore like() | | zeros underscore like() | ||
|- | |- | ||
| − | | | + | | 08:43 |
| ones() | | ones() | ||
|- | |- | ||
| − | | | + | | 08:44 |
| ones underscore like() | | ones underscore like() | ||
|- | |- | ||
| − | | | + | | 08:48 |
| Try the following, first check the value of a1, | | Try the following, first check the value of a1, | ||
|- | |- | ||
| − | | | + | | 08:52 |
| We see that a1 is a single dimensional array, | | We see that a1 is a single dimensional array, | ||
|- | |- | ||
| − | | | + | |08:56 |
|So type a1 and hit enter | |So type a1 and hit enter | ||
|- | |- | ||
| − | | | + | | 09:01 |
| So next now try a1 into 2 | | So next now try a1 into 2 | ||
|- | |- | ||
| − | | | + | |09:05 |
|So type a1 into 2 | |So type a1 into 2 | ||
|- | |- | ||
| − | | | + | | 09:09 |
| It returned a new array with all the elements multiplied by 2. | | It returned a new array with all the elements multiplied by 2. | ||
|- | |- | ||
| − | | | + | | 09:13 |
|Now let us again check the contents of a1 | |Now let us again check the contents of a1 | ||
|- | |- | ||
| − | | | + | | 09:19 |
| note that the value of a1 still remains the same. | | note that the value of a1 still remains the same. | ||
|- | |- | ||
| − | | | + | |09:23 |
|Similarly with addition,so type a1 plus 2 and hit enter and then type a1 | |Similarly with addition,so type a1 plus 2 and hit enter and then type a1 | ||
|- | |- | ||
| − | | | + | |09:36 |
| it returns a new array, with all the elements summed with two. | | it returns a new array, with all the elements summed with two. | ||
|- | |- | ||
| − | | | + | |09:41 |
|But again notice that the value of a1 has not been changed. | |But again notice that the value of a1 has not been changed. | ||
|- | |- | ||
| − | | | + | |09:46 |
|You may change the value of a1 by simply assigning the newly returned array as,a1 space plus=2 | |You may change the value of a1 by simply assigning the newly returned array as,a1 space plus=2 | ||
Revision as of 14:42, 10 July 2014
| Time | Narration |
| 00:01 | Hello friends and welcome to the spoken tutorial on 'Getting started with arrays'. |
| 00:06 | At the end of this tutorial, you will be able to,
|
| 00:26 | So Before beginning this tutorial,we would suggest you to complete the tutorial on "Getting started with Lists". |
| 00:35 | Arrays are homogeneous data structures. |
| 0:39 | Unlike lists, arrays cannot have heterogeneous data elements. |
| 00:45 | They can have only one type of data as their entries, be them all integers, strings, or maybe floats, but not a mix. |
| 00:55 | Arrays of a given length are comparatively much faster in mathematical operations than lists of the same length, because of the fact that they are homogeneous data structures. |
| 01:07 | Let us see how to create arrays. |
| 01:11 | Run your IPython interpreter with space hypen pylab option, to load the required modules to work with arrays. |
| 01:21 | So type ipython space hypen pylab |
| 01:28 | To create an array we will use the function array() as,a1 = array within brackets square brackets 1 comma 2 comma 3 comma 4 |
| 01:45 | Notice that we created a one dimensional array here. |
| 01:49 | Also notice that the object we passed to create an array is a list. |
| 01:54 | Now let us see how to create a two dimensional array. |
| 01:58 | We create two dimensional array by converting a list of lists to an array as,
a2 = array within brackets within square brackets 1 comma 2 comma 3 comma 4 comma then again within square brackets 5 comma 6 comma 7 comma 8 and hit enter. |
| 02:38 | Now let us use arrange() function to create the same array as before. |
| 02:45 | For that type ar = arrange within bracket 1 comma 9 and hit enter,so type
print ar to get the output. |
| 03:02 | So now, As you can see, we obtained a one dimensional array with elements from 1 to 8. |
| 03:12 | Now can we make it a two dimensional array of order 2 by 4? Yes,we can. |
| 03:20 | For this we will have to use the function reshape() , |
| 03:24 | So type ar.reshape brackets 2 comma 4 and hit enter |
| 03:33 | So type ar.reshape within brackets 4 comma 2
then ar = ar dot reshape within brackets 2,4 |
| 03:55 | Hence,we got our two-dimensional array. |
| 03:58 | Now, let us see how to convert a list object to an array. |
| 04:02 | We define a list,say l1 |
| 04:07 | So type l1 = within square brackets 1 comma 2 comma 3 comma 4 and hit enter |
| 04:16 | Now to convert this list to an array,we use the array function as, a3 = array within brackets l1 |
| 04:30 | To find the shape of an array we can use the method dot shape , |
| 04:36 | let us check the shape of the arrays we have created so far, |
| 04:44 | a2 dot shape object is a tuple, and it returned a tuple (2 comma 4). |
| 04:52 | A tuple is nothing but an ordered list of elements. |
| 04:56 | So Pause the video here, try out the following exercise and resume the video. |
| 05:12 | Find out the shape of the other arrays i.e. a1 comma a3 comma ar that we have created. |
| 05:22 | It can be done as
a1 dot shape a3 dot shape ar dot shape in the terminal |
| 05:37 | Now let us try to create a new array with a mix of elements and see what will happen, |
| 05:45 | So type a4 = array within brackets then square bracket 1 comma 2 comma 3 comma and single quote a string and hit enter |
| 06:07 | Well, we would expect an error as it has been previously mentioned that arrays handle elements with the same data type, but it didn't raise an error. |
| 06:16 | Let us check the values in the new array created. |
| 06:19 | So Type a4 in the terminal, |
| 06:27 | Did you notice it, all the elements have been implicitly type casted as strings, though our first three elements were meant to be integers. |
| 06:37 | Also,if you have noticed,we got something like 'dtype S8' in the output. |
| 06:44 | dtype is nothing but the data type which is the minimum type required to hold the objects in the sequence. |
| 06:52 | Let us now move on to study functions like zeros() function and ones() function. |
| 06:59 | For this ,we will have to create a matrix. |
| 07:02 | let us see how to create an identity matrix of a given size, this is a two-dimensional array in which all the diagonal elements are ones and rest of the elements are zeros. |
| 07:13 | We can create an identity matrix using the function identity() . |
| 07:18 | The function identity() takes an integer argument which specifies the size of the desired matrix, |
| 07:27 | As you can see the identity function returned a three by three square matrix with all the diagonal elements as one and the rest of the elements as zeros. |
| 07:43 | So type identity within brackets 3 |
| 07:48 | zeros() function accepts a tuple, which is the order of the array that we want to create, and it generates an array with all elements as zeros. |
| 07:59 | Let us create an array of the order four by five with all the elements zero. |
| 08:06 | We can do it using the method zeros(), |
| 08:10 | So type zeros within brackets then again in bracket 4 comma 5 and hit enter |
| 08:21 | Notice that we passed a tuple to the function zeros. |
| 08:25 | Pause the video here, try out the following exercise and resume the video. |
| 08:33 | So now we learnt two functions identity and zeros |
| 08:38 | Find out about the functions |
| 08:41 | zeros underscore like() |
| 08:43 | ones() |
| 08:44 | ones underscore like() |
| 08:48 | Try the following, first check the value of a1, |
| 08:52 | We see that a1 is a single dimensional array, |
| 08:56 | So type a1 and hit enter |
| 09:01 | So next now try a1 into 2 |
| 09:05 | So type a1 into 2 |
| 09:09 | It returned a new array with all the elements multiplied by 2. |
| 09:13 | Now let us again check the contents of a1 |
| 09:19 | note that the value of a1 still remains the same. |
| 09:23 | Similarly with addition,so type a1 plus 2 and hit enter and then type a1 |
| 09:36 | it returns a new array, with all the elements summed with two. |
| 09:41 | But again notice that the value of a1 has not been changed. |
| 09:46 | You may change the value of a1 by simply assigning the newly returned array as,a1 space plus=2 |
| 10:03 | Notice the change in elements of a by typing 'a' so type a and hit enter |
| 10:13 | so type a1 to get the output |
| 10:18 | We can use all the mathematical operations with arrays, |
| 10:22 | Now let us try this a1 = arrays within brackets square brackets 1 comma 2 comma 3 comma 4
and hit enter |
| 10:45 | then a2 = array within brackets square brackets 1 comma 2 comma 3 comma 4
then type a1 + a2 and hit enter |
| 11:07 | This returns an array with element by addition |
| 11:15 | So try out a1 into a2 |
| 11:23 | a1 into a2 returns an array with element by element multiplication, |
| 11:31 | And notice that it does not perform matrix multiplication. |
| 11:37 | This brings us to the end of the end of this tutorial. |
| 11:41 | In this tutorial, we have learnt to,
1. Create an array using the array() function. |
| 11:46 | 2. Convert a list to an array. |
| 11:49 | 3. Perform some basic operations on arrays like addition,multiplication. |
| 11:53 | 4. Use functions like - .shape - arrange() - .reshape - zeros() & zeros underscore like() - ones() & ones underscore like() |
| 12:05 | Here are some self assessment questions for you to solve |
| 12:09 | 1.First one, x = array within brackets square bracket 1 comma 2 comma 3 comma square bracket 5 comma 6 comma 7 is a valid statement |
| 12:23 | So IS True or False? |
| 12:27 | 2. What does the ones underscore like() function do? |
| 12:31 | A. Returns an array of ones with the same shape and type as a given array. |
| 12:37 | B. Return a new array of given shape and type, filled with ones. |
| 12:43 | Now Read the statements and answer, |
| 12:47 | Only statement A is correct. |
| 12:49 | Only statement B is correct. |
| 12:51 | Both statement A and B are correct. |
| 12:53 | Both statement A and B are incorrect. |
| 12:56 | So let's find the answers, |
| 12:59 | 1. The answer is False. |
| 13:02 | The correct way would be to assign the elements as a list of lists and then convert it to an array |
| 13:10 | Type x = array within brackets square brackets 1 comma 2 comma 3 comma within brackets 5 comma 6 comma 7 |
| 13:21 | 1. The function ones underscores like() returns an array of ones with the same shape and type as a given array. |
| 13:29 | Hope you have enjoyed this tutorial and found it useful. |
| 13:31 | Thank you! |
