Python/C3/Conditionals/English-timed

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!

Contributors and Content Editors

Gaurav, Minal, PoojaMoolya, Sneha