Difference between revisions of "Python/C3/Conditionals/English-timed"
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{| border=1 | {| border=1 | ||
− | ! | + | !Time |
!Narration | !Narration | ||
|- | |- | ||
− | | | + | | 00:01 |
| Hello friends and Welcome to the tutorial on 'Conditionals'. | | Hello friends and Welcome to the tutorial on 'Conditionals'. | ||
|- | |- | ||
− | | | + | | 00:05 |
| At the end of this tutorial, you will be able to, | | At the end of this tutorial, you will be able to, | ||
− | + | Use if/else blocks. | |
− | + | Use if/elif/else blocks. | |
− | + | Use the Ternary conditional statement - C if X else Y. | |
− | + | ||
|- | |- | ||
− | | | + | | 00:25 |
| To begin with let us start ipython, | | To begin with let us start ipython, | ||
|- | |- | ||
− | | | + | |00:29 |
|So type ipython in the terminal | |So type ipython in the terminal | ||
|- | |- | ||
− | | | + | | 00:36 |
| Whenever we have two possible states that can occur depending on a a certain condition, we can use if/else construct in Python. | | Whenever we have two possible states that can occur depending on a a certain condition, we can use if/else construct in Python. | ||
|- | |- | ||
− | | | + | | 00:45 |
| For example, say, we have a variable a which stores integers and we are required to find out whether a is even or odd. | | For example, say, we have a variable a which stores integers and we are required to find out whether a is even or odd. | ||
|- | |- | ||
− | | | + | | 00:52 |
| Let's say the value of a is 5. | | Let's say the value of a is 5. | ||
|- | |- | ||
− | | | + | |00:55 |
|So type a=5 | |So type a=5 | ||
|- | |- | ||
− | | | + | | 00:59 |
| In such a case we can write the if/else block as | | In such a case we can write the if/else block as | ||
|- | |- | ||
− | | | + | |01:04 |
|In command line if a percentage 2 == 0 colon | |In command line if a percentage 2 == 0 colon | ||
− | + | print in double quotes Even | |
− | + | else colon | |
− | + | print in double quotes Odd | |
− | + | ||
|- | |- | ||
− | | | + | | 01:37 |
| If a is divisible by 2, i.e., the result of "a modulo 2" is 0, it prints "Even", otherwise it prints "Odd". | | If a is divisible by 2, i.e., the result of "a modulo 2" is 0, it prints "Even", otherwise it prints "Odd". | ||
|- | |- | ||
− | | | + | |01:51 |
| Note that in such a case, only one of the two blocks gets executed depending on whether the condition is True or <tt> False. | | Note that in such a case, only one of the two blocks gets executed depending on whether the condition is True or <tt> False. | ||
|- | |- | ||
− | | | + | |01:58 |
| There is a very important syntactic element to understand here. | | There is a very important syntactic element to understand here. | ||
|- | |- | ||
− | | | + | |02:03 |
| Every code block begins with a line that ends with a colon, in this example the if and the else lines. | | Every code block begins with a line that ends with a colon, in this example the if and the else lines. | ||
|- | |- | ||
− | | | + | |02:15 |
| Also, all the statements inside a code block are intended by 4 spaces. | | Also, all the statements inside a code block are intended by 4 spaces. | ||
|- | |- | ||
− | | | + | |02:21 |
| Hitting enter twice, ends the code block. | | Hitting enter twice, ends the code block. | ||
|- | |- | ||
− | | | + | |02:25 |
| The if/else blocks work for a condition, which can take one of two states. | | The if/else blocks work for a condition, which can take one of two states. | ||
|- | |- | ||
− | | | + | |02:31 |
| But what do we do for conditions, which can take more than two states? | | But what do we do for conditions, which can take more than two states? | ||
|- | |- | ||
− | | | + | | 02:38 |
| Python provides if/elif/else blocks, for such conditions. | | Python provides if/elif/else blocks, for such conditions. | ||
|- | |- | ||
− | | | + | | 02:47 |
| For example. | | For example. | ||
|- | |- | ||
− | | | + | | 02:49 |
| We have a variable a which holds integer values. | | We have a variable a which holds integer values. | ||
|- | |- | ||
− | | | + | |02:52 |
| We need to print "positive" if a is positive, "negative" if it is negative or "zero" if it is 0. | | We need to print "positive" if a is positive, "negative" if it is negative or "zero" if it is 0. | ||
|- | |- | ||
− | | | + | |03:04 |
| Let us use if/elif/else ladder for it. | | Let us use if/elif/else ladder for it. | ||
|- | |- | ||
− | | | + | |03:09 |
| For the purposes of testing our code let us assume that the value of a is -3 | | For the purposes of testing our code let us assume that the value of a is -3 | ||
|- | |- | ||
− | | | + | |03:16 |
|Type a = -3 | |Type a = -3 | ||
− | |||
if a greater than 0 colon | if a greater than 0 colon | ||
− | + | print within double quotes positive | |
elif a less than 0 colon | elif a less than 0 colon | ||
− | + | print in double quotes negative | |
− | + | else colon | |
− | + | print within double quotes zero | |
|- | |- | ||
− | | | + | | 04:17 |
| All the syntax and rules as said for if/else statements hold the same. | | All the syntax and rules as said for if/else statements hold the same. | ||
|- | |- | ||
− | | | + | | 04:24 |
| The only addition here is the elif statement which can have another condition of its own. | | The only addition here is the elif statement which can have another condition of its own. | ||
|- | |- | ||
− | | | + | | 04:30 |
| Here too, exactly one block of code is executed -- the block of code which first evaluates to True . | | Here too, exactly one block of code is executed -- the block of code which first evaluates to True . | ||
|- | |- | ||
− | | | + | | 04:41 |
| Even if there is a situation where multiple conditions evaluate to True, all the subsequent conditions other than the first one, which evaluates to True, are neglected. | | Even if there is a situation where multiple conditions evaluate to True, all the subsequent conditions other than the first one, which evaluates to True, are neglected. | ||
|- | |- | ||
− | | | + | | 04:51 |
| Consequently, the else block gets executed if and only if all the conditions evaluate to False. | | Consequently, the else block gets executed if and only if all the conditions evaluate to False. | ||
|- | |- | ||
− | | | + | | 04:59 |
| Also, the else block in both if/else statement and if/elif/else is optional. | | Also, the else block in both if/else statement and if/elif/else is optional. | ||
|- | |- | ||
− | | | + | | 05:08 |
| We can have a single if statement or just if/elif statements without having else block at all. | | We can have a single if statement or just if/elif statements without having else block at all. | ||
|- | |- | ||
− | | | + | | 05:17 |
| Also, there can be any number of elif's within an if/elif/else ladder. | | Also, there can be any number of elif's within an if/elif/else ladder. | ||
|- | |- | ||
− | | | + | | 05:26 |
| For example | | For example | ||
|- | |- | ||
− | | | + | |05:28 |
|Type if user == in single quotes admin colon | |Type if user == in single quotes admin colon | ||
− | + | elif user == in single quotes moderator colon | |
− | + | elif user == in single quotes client colon | |
|- | |- | ||
− | | | + | | 05:47 |
| Note that there are multiple elif blocks and there is no else block. | | Note that there are multiple elif blocks and there is no else block. | ||
|- | |- | ||
− | | | + | | 05:53 |
| 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. | ||
|- | |- | ||
− | | | + | | 05:57 |
| '''Given a number, num. Write an if else block to print num, as is,''' | | '''Given a number, num. Write an if else block to print num, as is,''' | ||
|- | |- | ||
− | | | + | |06:05 |
| if it is divisible by 10, else print 10 into num. | | if it is divisible by 10, else print 10 into num. | ||
|- | |- | ||
− | | | + | | 06:12 |
| The solution is on your screen. | | The solution is on your screen. | ||
|- | |- | ||
− | | | + | |06:14 |
|if num modulo 10 == 0 colon | |if num modulo 10 == 0 colon | ||
− | + | print num | |
− | + | else colon | |
− | + | print 10 star num | |
|- | |- | ||
− | | | + | | 06:29 |
| In addition to these conditional statements, Python provides a very convenient ternary conditional operator. | | In addition to these conditional statements, Python provides a very convenient ternary conditional operator. | ||
|- | |- | ||
− | | | + | | 06:35 |
| Let us take the following example where we read the marks from a data file which is obtained as a string as we read a file. | | Let us take the following example where we read the marks from a data file which is obtained as a string as we read a file. | ||
|- | |- | ||
− | | | + | | 06:43 |
| The marks can be in the range of 0 to 100 or 'AA' if the student is absent. | | The marks can be in the range of 0 to 100 or 'AA' if the student is absent. | ||
|- | |- | ||
− | | | + | | 06:51 |
| In such a case, to obtain the marks as an integer, we can use the ternary conditional operator. | | In such a case, to obtain the marks as an integer, we can use the ternary conditional operator. | ||
|- | |- | ||
− | | | + | | 06:58 |
| Let us say the string score is stored in score underscore str variable | | Let us say the string score is stored in score underscore str variable | ||
|- | |- | ||
− | | | + | |07:05 |
|So type score underscore str = in single quotes AA | |So type score underscore str = in single quotes AA | ||
|- | |- | ||
− | | | + | | 07:13 |
| Now let us use the ternary conditional operator | | Now let us use the ternary conditional operator | ||
|- | |- | ||
− | | | + | |07:19 |
|Type score = int within bracket score underscore str if score underscore str exclamation = in single quotes AA else 0 | |Type score = int within bracket score underscore str if score underscore str exclamation = in single quotes AA else 0 | ||
|- | |- | ||
− | | | + | | 07:54 |
| '''Given a number, num. Write a ternary operator to print num, as is,''' | | '''Given a number, num. Write a ternary operator to print num, as is,''' | ||
|- | |- | ||
− | | | + | | 08:01 |
| if it is divisible by 10, else print 10 star num. | | if it is divisible by 10, else print 10 star num. | ||
|- | |- | ||
− | | | + | | 08:08 |
| The solution is on your screen. | | The solution is on your screen. | ||
|- | |- | ||
− | | | + | | 08:11 |
| print num if num modulo 10 == 0 else 10 star num | | print num if num modulo 10 == 0 else 10 star num | ||
|- | |- | ||
− | | | + | | 08:19 |
| Moving on, there are certain situations where we will have no operations or statements within a block of code. | | Moving on, there are certain situations where we will have no operations or statements within a block of code. | ||
|- | |- | ||
− | | | + | | 08:27 |
| For example, we have a code where we are waiting for the keyboard input. | | For example, we have a code where we are waiting for the keyboard input. | ||
|- | |- | ||
− | | | + | | 08:32 |
| If the user enters "c", "d" or "x" as the input, we would perform some operation; nothing otherwise. | | If the user enters "c", "d" or "x" as the input, we would perform some operation; nothing otherwise. | ||
|- | |- | ||
− | | | + | | 08:42 |
| In such cases "pass" statement comes very handy | | In such cases "pass" statement comes very handy | ||
|- | |- | ||
− | | | + | | 08:49 |
| '''a = raw underscore input Enter 'c' to calculate and exit, 'd' to display the existing''' | | '''a = raw underscore input Enter 'c' to calculate and exit, 'd' to display the existing''' | ||
|- | |- | ||
− | | | + | | 09:04 |
| results exit and 'x' to exit and any other key to continue | | results exit and 'x' to exit and any other key to continue | ||
|- | |- | ||
− | | | + | | 09:12 |
| '''if a == in single quote c colon''' | | '''if a == in single quote c colon''' | ||
|- | |- | ||
− | | | + | | 09:18 |
| '''elif a == in single quote d colon''' | | '''elif a == in single quote d colon''' | ||
|- | |- | ||
− | | | + | | 09:23 |
| '''elif a == in single quote x colon''' | | '''elif a == in single quote x colon''' | ||
|- | |- | ||
− | | | + | | 09:29 |
| '''else colon''' | | '''else colon''' | ||
|- | |- | ||
− | | | + | | 09:32 |
| pass | | pass | ||
|- | |- | ||
− | | | + | | 09:35 |
| In this case "pass" statement acts as a place holder for the block of code. | | In this case "pass" statement acts as a place holder for the block of code. | ||
|- | |- | ||
− | | | + | | 09:41 |
| It is equivalent to a null operation. | | It is equivalent to a null operation. | ||
|- | |- | ||
− | | | + | | 09:45 |
− | | It literally does nothing. | + | | It literally does nothing. It can used as a place holder when the actual code implementation for a particular block of code is not known yet but has to be filled up later. |
− | + | ||
− | + | ||
− | + | ||
− | + | ||
|- | |- | ||
− | | | + | | 09:56 |
| This brings us to the end of the tutorial. | | This brings us to the end of the tutorial. | ||
|- | |- | ||
− | | | + | | 09:59 |
− | | In this tutorial, we have learnt to, | + | | In this tutorial, we have learnt to, Understand the conditional statements in Python. |
|- | |- | ||
| 10:04 | | 10:04 | ||
− | | | + | |Use if/else statement. |
|- | |- | ||
| 10:06 | | 10:06 | ||
− | | | + | | Use if/elif/else statement. |
|- | |- | ||
| 10:09 | | 10:09 | ||
− | | | + | | Apply the ternary conditional statement - C if X else Y. |
|- | |- | ||
| 10:14 | | 10:14 | ||
− | | | + | | Use "pass" statement. |
|- | |- | ||
Line 323: | Line 316: | ||
|- | |- | ||
| 10:21 | | 10:21 | ||
− | | | + | | Use conditional statements for the following. |
|- | |- | ||
Line 331: | Line 324: | ||
|- | |- | ||
| 10:30 | | 10:30 | ||
− | | | + | | Convert the if else ladder below into a ternary conditional statement. |
|- | |- | ||
| 10:39 | | 10:39 | ||
| x = 20 | | x = 20 | ||
− | + | if x greater than 10 colon | |
− | + | print x multiply by 100 | |
− | + | else colon | |
− | + | print x | |
|- | |- | ||
Line 347: | Line 340: | ||
|- | |- | ||
| 10:52 | | 10:52 | ||
− | | | + | | We can use the if/else statements as |
− | + | if time less than 12 colon | |
− | + | print in double quotes Good Morning | |
− | + | else colon | |
− | + | print in double quotes Hello | |
|- | |- | ||
| 11:06 | | 11:06 | ||
− | | | + | |The if else ladder can be converted to a ternary conditional statement as print x multiply by 100 if x greater than 10 else x |
− | + | ||
|- | |- |
Latest revision as of 12:20, 27 March 2017
Time | Narration |
---|---|
00:01 | Hello friends and Welcome to the tutorial on 'Conditionals'. |
00:05 | At the end of this tutorial, you will be able to,
Use if/else blocks. Use if/elif/else blocks. Use the Ternary conditional statement - C if X else Y. |
00:25 | To begin with let us start ipython, |
00:29 | So type ipython in the terminal |
00:36 | Whenever we have two possible states that can occur depending on a a certain condition, we can use if/else construct in Python. |
00:45 | For example, say, we have a variable a which stores integers and we are required to find out whether a is even or odd. |
00:52 | Let's say the value of a is 5. |
00:55 | So type a=5 |
00:59 | In such a case we can write the if/else block as |
01:04 | In command line if a percentage 2 == 0 colon
print in double quotes Even else colon print in double quotes Odd |
01:37 | If a is divisible by 2, i.e., the result of "a modulo 2" is 0, it prints "Even", otherwise it prints "Odd". |
01:51 | Note that in such a case, only one of the two blocks gets executed depending on whether the condition is True or False. |
01:58 | There is a very important syntactic element to understand here. |
02:03 | Every code block begins with a line that ends with a colon, in this example the if and the else lines. |
02:15 | Also, all the statements inside a code block are intended by 4 spaces. |
02:21 | Hitting enter twice, ends the code block. |
02:25 | The if/else blocks work for a condition, which can take one of two states. |
02:31 | But what do we do for conditions, which can take more than two states? |
02:38 | Python provides if/elif/else blocks, for such conditions. |
02:47 | For example. |
02:49 | We have a variable a which holds integer values. |
02:52 | We need to print "positive" if a is positive, "negative" if it is negative or "zero" if it is 0. |
03:04 | Let us use if/elif/else ladder for it. |
03:09 | For the purposes of testing our code let us assume that the value of a is -3 |
03:16 | Type a = -3
if a greater than 0 colon print within double quotes positive elif a less than 0 colon print in double quotes negative else colon print within double quotes zero |
04:17 | All the syntax and rules as said for if/else statements hold the same. |
04:24 | The only addition here is the elif statement which can have another condition of its own. |
04:30 | Here too, exactly one block of code is executed -- the block of code which first evaluates to True . |
04:41 | Even if there is a situation where multiple conditions evaluate to True, all the subsequent conditions other than the first one, which evaluates to True, are neglected. |
04:51 | Consequently, the else block gets executed if and only if all the conditions evaluate to False. |
04:59 | Also, the else block in both if/else statement and if/elif/else is optional. |
05:08 | We can have a single if statement or just if/elif statements without having else block at all. |
05:17 | Also, there can be any number of elif's within an if/elif/else ladder. |
05:26 | For example |
05:28 | Type if user == in single quotes admin colon
elif user == in single quotes moderator colon elif user == in single quotes client colon |
05:47 | Note that there are multiple elif blocks and there is no else block. |
05:53 | Pause the video here, try out the following exercise and resume the video. |
05:57 | Given a number, num. Write an if else block to print num, as is, |
06:05 | if it is divisible by 10, else print 10 into num. |
06:12 | The solution is on your screen. |
06:14 | if num modulo 10 == 0 colon
print num else colon print 10 star num |
06:29 | In addition to these conditional statements, Python provides a very convenient ternary conditional operator. |
06:35 | Let us take the following example where we read the marks from a data file which is obtained as a string as we read a file. |
06:43 | The marks can be in the range of 0 to 100 or 'AA' if the student is absent. |
06:51 | In such a case, to obtain the marks as an integer, we can use the ternary conditional operator. |
06:58 | Let us say the string score is stored in score underscore str variable |
07:05 | So type score underscore str = in single quotes AA |
07:13 | Now let us use the ternary conditional operator |
07:19 | Type score = int within bracket score underscore str if score underscore str exclamation = in single quotes AA else 0 |
07:54 | Given a number, num. Write a ternary operator to print num, as is, |
08:01 | if it is divisible by 10, else print 10 star num. |
08:08 | The solution is on your screen. |
08:11 | print num if num modulo 10 == 0 else 10 star num |
08:19 | Moving on, there are certain situations where we will have no operations or statements within a block of code. |
08:27 | For example, we have a code where we are waiting for the keyboard input. |
08:32 | If the user enters "c", "d" or "x" as the input, we would perform some operation; nothing otherwise. |
08:42 | In such cases "pass" statement comes very handy |
08:49 | a = raw underscore input Enter 'c' to calculate and exit, 'd' to display the existing |
09:04 | results exit and 'x' to exit and any other key to continue |
09:12 | if a == in single quote c colon |
09:18 | elif a == in single quote d colon |
09:23 | elif a == in single quote x colon |
09:29 | else colon |
09:32 | pass |
09:35 | In this case "pass" statement acts as a place holder for the block of code. |
09:41 | It is equivalent to a null operation. |
09:45 | It literally does nothing. It can used as a place holder when the actual code implementation for a particular block of code is not known yet but has to be filled up later. |
09:56 | This brings us to the end of the tutorial. |
09:59 | In this tutorial, we have learnt to, Understand the conditional statements in Python. |
10:04 | Use if/else statement. |
10:06 | Use if/elif/else statement. |
10:09 | Apply the ternary conditional statement - C if X else Y. |
10:14 | Use "pass" statement. |
10:18 | Here are some self assessment questions for you to solve |
10:21 | Use conditional statements for the following. |
10:23 | Given a variable time , print Good Morning if it is less than 12, otherwise Hello . |
10:30 | Convert the if else ladder below into a ternary conditional statement. |
10:39 | x = 20
if x greater than 10 colon print x multiply by 100 else colon print x |
10:48 | And now lets look at the answers, |
10:52 | We can use the if/else statements as
if time less than 12 colon print in double quotes Good Morning else colon print in double quotes Hello |
11:06 | The if else ladder can be converted to a ternary conditional statement as print x multiply by 100 if x greater than 10 else x |
11:17 | Hope you have enjoyed this tutorial and found it useful. |
11:20 | Thank you! |