4 .. Clearly state the objectives of the LO (along with RBT level)

     4 .. By the end of this tutorial, you will be able to 

     5 

     6 .. * Use if/else blocks 

     7 .. * Use if/elif/else blocks

     8 .. * Use the Ternary conditional statement - C if X else Y

     9 

    10 .. to check conditions in your programs. 

    11 

     9 ..   1. Name of LO-1

    16 ..   1. Basic datatypes and operators

    10 ..   2. Name of LO-2

    17 

    11 ..   3. Name of LO-3

    24 Hello friends. Welcome to this spoken tutorial on Getting started with

    30 Hello friends. Welcome to this spoken tutorial on Conditionals

    25 strings.

    43 Python. Say for example we have a variable "a" which stores integers

    48 Python. 

    44 and we are required to find out whether the value of the variable "a"

    49 

    45 is an even number or an odd number. To test out conditional statements

    50 For example, say, we have a variable ``a`` which stores integers and

    46 as an example, let us say the value of the variable "a" is 5::

    51 we are required to find out whether ``a`` is even or odd.  an even

    52 number or an odd number. Let's say the value of ``a`` is 5, now.

    53 ::

    57 When the value of the variable "a" is divided by 2 and the remainder

    64 If ``a`` is divisible by 2, i.e., the result of "a modulo 2" is 0, it

    58 is 0 i.e. the result of the operation "a modulo 2" is 0 the condition

    65 prints "Even", otherwise it prints "Odd". 

    59 "a % 2 == 0" evaluates to True, so the code within the if block gets

    66 

    60 executed. This means that the value of "a" is Even. 

    67 Note that in such a case, only one of the two blocks gets executed

    61 

    68 depending on whether the condition is ``True`` or ``False``.

    62 If the operation "a modulo 2" is not 0 the condition "a % 2 == 0"

    69 

    63 evaluates to False and hence the code block within else gets executed

    70 There is a very important sytactic element to understand here. Every

    64 which means that the value of "a" is Odd. 

    71 code block begins with a line that ends with a ``:``, in this example

    65 

    72 the ``if`` and the ``else`` lines. Also, all the statements inside a

    66 Note in such a case only one of the two blocks get executed depending

    73 code block are intended by 4 spaces. Returning to the previous

    67 on whether the condition is True or False.

    74 indentation level, ends the code block. 

    68 

    75 

    69 There is a very important sytactic element to understand here. All the

    76 The if/else blocks work for a condition, which can take one of two

    70 statements which are inside a certain code block are indented by 4

    77 states. What do we do for conditions, which can take more than two

    71 spaces. The statement which starts a new code block after it, i.e. the

    78 states? 

    72 if statement in this example ends with a colon (:). So the next

    79 

    73 immediate line will be inside the if block and hence indented by 4

    80 Python provides if/elif/else blocks, for such conditions. Let us take

    74 spaces. To come out of the code block we have to come back to the

    81 an example. We have a variable ``a`` which holds integer values. We

    75 previous indentation level as shown in the else line here. Again the

    82 need to print "positive" if ``a`` is positive, "negative" if

    76 line following else will be in a new block so else line ends with a

    83 it is negative or "zero" if it is 0. 

    77 colon and the following block of code is indented by 4.

    84 

    78 

    85 Let us use if/elif/else ladder for it. For the purposes of testing our

    79 As we use if/else statement when we have a condition which can take

    86 code let us assume that the value of a is -3::

    80 one of the two states, we may have conditions which can take more than

    81 two states. In such a scenario Python provides if/elif/else

    82 statements. Let us take an example. We have a variable "a" which holds

    83 integer values. We need to print "positive" if the value of a is

    84 positive, "negative" if it is negative and "zero" if the value of the

    85 variable "a" is 0. Let us use if/elif/else ladder for it. For the

    86 purposes of testing our code let us assume that the value of a is -3::

    97 This if/elif/else ladder is self explanatory. All the syntax and rules

    97 All the syntax and rules as said for if/else statements hold. The only

    98 as said for if/else statements hold. The only addition here is the

    98 addition here is the ``elif`` statement which can have another

    99 elif statement which can have another condition of its own.

    99 condition of its own.

   100 

   100 

   101 Here, exactly one block of code is executed and that block of code

   101 Here too, exactly one block of code is executed -- the block of code

   102 corresponds to the condition which first evaluates to True. Even if

   102 which first evaluates to ``True``. Even if there is a situation where

   103 there is a situation where multiple conditions evaluate to True all

   103 multiple conditions evaluate to True all the subsequent conditions

   104 the subsequent conditions other than the first one which evaluates to

   104 other than the first one which evaluates to True are neglected.

   105 True are neglected. Consequently, the else block gets executed if and

   105 Consequently, the else block gets executed if and only if all the

   106 only if all the conditions evaluate to False.

   106 conditions evaluate to False.

   107 

   107 

   108 Also, the else block in both if/else statement and if/elif/else is

   108 Also, the ``else`` block in both if/else statement and if/elif/else is

   150 Moving on, there are certain situations where we will have to no

   156 Following is an exercise that you must do. 

   151 operations or statements within the block of code. For example, we

   157 

   152 have a code where we are waiting for the keyboard input. If the user

   158 %% %%     

   153 enters "s" as the input we would perform some operation nothing

   159 

   160 Please, pause the video here. Do the exercise and then continue. 

   161 

   162 Moving on, there are certain situations where we will have no

   163 operations or statements within a block of code. For example, we have

   164 a code where we are waiting for the keyboard input. If the user enters

   165 "c", "d" or "x" as the input we would perform some operation nothing

   170 nothing. So "pass" statement can be used as a null operation

   182 nothing. It can used as a place holder when the actual code

   171 statement, or it can used as a place holder when the actual code