Difference between revisions of "Python-3.4.3/C3/Conditional-Statements/English"

Objectives

• if/else blocks
• if/elif/else blocks
• Ternary conditional statement and
• Pass statement

System Specifications

• Ubuntu Linux 16.04 operating system
• Python 3.4.3
• IPython 5.1.0

Pre-requisite

• basic data types and operators
• strings and Input/Output statements

If not, see the relevant Python tutorials on this website.

if condition

if condition is used to decide whether to execute the statements in the if block or not.

Here is the syntax.

if else condition

Box line by line

Highlight :

Highlight 4 spaces

When the test condition is true, it will execute the body of if.

If the condition is False, body of the else is executed.

Note that, if and else statements end with a colon.

This denotes the beginning of the code block of True or False condition.

All the statements inside a code block are indented by 4 spaces.

Open the terminal.

press Enter

From here onwards, remember to press the Enter key after typing every command on the terminal.

Enter number 4 and press Enter

Type, num is equal to int inside brackets input open and close brackets

Enter 4 and press Enter

if num % 2 == 0: print ('Even')else: print ('Odd')

print inside brackets inside single quotes Even

Press backspace four times and type, else colon

print inside brackets inside single quotes Odd

Highlight the spaces

Press Enter twice to get the output.

As expected, it displays Even as output.

Note that, the statements inside a code block are indented by 4 spaces automatically.

<<PAUSE>>

elif statement

All the syntax and rules for elif are same as if/else statements.

In if/else, only one condition is checked.

But in elif statement multiple conditions can be checked.

if/elif Example

Box line by line

The first block of code is executed as soon as one of the conditions evaluates to True.

All the subsequent conditions in elif ladder are not checked.

The else block gets executed if all the conditions in elif ladder are evaluated to False.

Type, a is equal to minus 3

We have a variable a which holds integer value as -3.

if a > 0:

print ("positive")

elif a < 0:

print ("negative")

else:

print ("zero")

Highlight positive

Highlight negative

Highlight zero

This program will print

• "positive" if a is positive,
• "negative" if it is negative or
• "zero" if it is 0.

Point to the output

Highlight elif

For example, based on the type of user the corresponding operations are performed using elif.

Note that else block is optional in both if/else and if/elif/else statements.

Try this exercise and then resume the video.

Assignment 1

Write an if else block to print num, if it is divisible by 10, else print 10 asterisk num.

<<PAUSE>>

Ternary operator

syntax:

[A] if <condition> else [B]

Ternary operator allows to test a condition in a single line replacing the multiline if-else.

It can reduce the code size and increase the readability of the code.

Here is the syntax.

Type, a is equal to 4

We got the required output.

Try this exercise and then resume the video.

Assignment 2

Write a ternary operator to print n, if it is divisible by 10, else print 10 asterisk n.

<<PAUSE>>

Pass statement

The pass statement acts as a null operation (i.e) nothing happens when it executes.

It works as a placeholder for a block of code.

It is used in a code block where actual code implementation is not known yet.

Type a is equal to 11

if a%2 == 0: print(‘even’)else: pass

If a divided by 2 equals to zero, if block is executed.

Else no operation is performed.

Here a divided by 2 is not 0.

So no operation is performed and nothing is displayed as output.

Summary

Let us summarize.

In this tutorial, we have learnt the conditional statements such as,

• if/else statement
• if/elif/else statement
• Ternary conditional statement and
• Pass statement

<<PAUSE>>

Evaluation

1. Given a variable t.

Print Good Morning if it is less than 12, otherwise print Hello. Use if else statement

2.Convert the below if else code into ternary conditional statement.

Solutions

1. The following code gives the required output.
2. Use the following statement to convert the if else code into a ternary statement

Acknowledgment

http://spoken-tutorial.org

For more details, visit this website.