Introduction to Python

Chapter 17 - if-else Selection Structure

IF - ELSE Statement in Python

Definition
- else condition can be optionally used to define an alternate block of statements to be executed if the boolean expression in the if condition evaluates to False
Purpose
- In programming languages, The else keyword is used in conditional statements (if statements), is an alternative statement that is executed if the result of a previous test condition evaluates to false
Importance
- The else keyword is used in conditional statements (if statements), and decides what to do if the condition is False
Suitable to Use
- An else statement contains the block of code that executes if the conditional expression in the if statement do not meet
- The if-else structure works well in situations in which you want Python to always execute one of two possible actions. In a simple if-else chain like this, one of the two actions will always be executed
- The if-else statement evaluates test expression and will execute the body of if only when the test condition is True

				
					'''
if Condition is True the block will be executed otherwise the control will move to the else statement and execute the else block
'''

if condition: 
    <statement(s)01>
    <statement(s)02>
    <statement(s)03>
    ….
    <statement(s)N>
else:
    <statement(s)01>
    <statement(s)02>
    <statement(s)03>
    ….
    <statement(s)N>
endif

				
					'''
__author__ = Ms. Samavi Salman
__copyright__= Copyright I 2020 Ms. Samavi Salman
__license__ = Public Domain
__version__ = 1.0

'''

try:

    print("Before If-Statement") 
    if 5 > 7:
        print("Statement 01 - Condition is True")
    else:
        print("Statement 01 - Condition is False")
    print("After if-Statement")
except:
    print("Runtime Error")

Execution of Code (Dry Run)
Python Statement	Calculations	Variable(s)	Output
try:
print(“Before If-Statement”)			Before If-Statement
If 5 > 7:	Decision Making – Check Whether Condition is True or False 5 > 7 False(i.e., Statement(s) will be executed after if-Statement)		Before If-Statement
print(“Statement 01 – Condition is True”)	This Statement will not be executed because Condition is False in above if-Statement (see Output Screen)		Before If-Statement
else:			Before If-Statement
print(“Statement 01 – Condition is False”)	This Statement will be executed because Condition is False in above if-Statement (see Output Screen)		Before If-Statement Statement 01 – Condition is False
print(“After if-Statement”)			Before If-Statement Statement 01 – Condition is False After if-Statement
except:			Before If-Statement Statement 01 – Condition is False After if-Statement
print(“Runtime Error”)			Before If-Statement Statement 01 – Condition is False After if-Statement

				
					'''
__author__ = Ms. Samavi Salman
__copyright__= Copyright I 2020 Ms. Samavi Salman
__license__ = Public Domain
__version__ = 1.0
'''

try:
    number = 10
    print("Before If-Statement") 
    if 20 >= number:
        print("Statement 01 - Condition is True")
   else:
        print("Statement 01 - Condition is False")
    print("After if-Statement")
except:
    print("Runtime Error")

Execution of Code (Dry Run)
Python Statement	Calculations	Variable(s)	Output
try:
number = 10		number = 10
print(“Before If-Statement”)		number = 10	Before If-Statement
if 20 >= number:	Decision Making – Check Whether Condition is True or False 20 >= number 20 >= 10 True (i.e., Statement(s) will be executed after if-Statement)	number = 10	Before If-Statement
print(“Statement 01 – Condition is True”)	This Statement will be executed because Condition is True in above if-Statement (see Output Screen)	number = 10	Before If-Statement Statement 01 – Condition is True
else:		number = 10	Before If-Statement
print(“Statement 01 – Condition is False”)	This Statement will not be executed because Condition is True in above if-Statement (see Output Screen)	number = 10	Before If-Statement
print(“After if-Statement”)		number = 10	Before If-Statement Statement 01 – Condition is True After if-Statement
except:		number = 10	Before If-Statement Statement 01 – Condition is True After if-Statement
print(“Runtime Error”)		number = 10	Before If-Statement Statement 01 – Condition is True After if-Statement

				
					'''
__author__ = Ms. Samavi Salman
__copyright__= Copyright I 2020 Ms. Samavi Salman
__license__ = Public Domain
__version__ = 1.0
'''

try:
    number1 = 100
    number2 = 100
    print("Before If-Statement") 
    if number1 != number2:
        print("Statement 01 - Condition is True")
        print("Statement 02 - number1 and number2 are not equal")
    else:
        print("Statement 01 - Condition is False")
        print("Statement 02 - number1 and number2 are equal")
    print("After if-Statement")
except:
    print("Runtime Error")

Execution of Code (Dry Run)
Python Statement	Calculations	Variable(s)	Output
number1 = 100
number2 = 100		number1 = 100
print(“Before If-Statement”)		number2 = 100
if number1 != number2:	Decision Making – Check Whether Condition is True or False number1 != number2 100 == 100 False (i.e., Statement(s) will be executed after if-Statement)	number1 = 100 number2 = 100	Before If-Statement
print(“Statement 01 – Condition is True”)	This Statement will not be executed because Condition is False in above if-Statement (see Output Screen)	number1 = 100 number2 = 100	Before If-Statement
print(“Statement 02 – number1 and number2 are not equal”)	This Statement will not be executed because Condition is False in above if-Statement (see Output Screen)	number1 = 100 number2 = 100	Before If-Statement
else:		number1 = 100 number2 = 100	Before If-Statement
print(“Statement 01 – Condition is False”)	This Statement will be executed because Condition is False in above if-Statement (see Output Screen)	number1 = 100 number2 = 100	Before If-Statement Statement 01 – Condition is False
print(“Statement 02 – number1 and number2 are equal”)	This Statement will be executed because Condition is False in above if-Statement (see Output Screen)	number1 = 100 number2 = 100	Before If-Statement Statement 01 – Condition is False Statement 02 – number1 and number2 are equal
print(“After if-Statement”)		number1 = 100 number2 = 100	Before If-Statement Statement 01 – Condition is False Statement 02 – number1 and number2 are equal After if-Statement
except:		number1 = 100 number2 = 100	Before If-Statement Statement 01 – Condition is False Statement 02 – number1 and number2 are equal After if-Statement
print(“Runtime Error”)		number1 = 100 number2 = 100	Before If-Statement Statement 01 – Condition is False Statement 02 – number1 and number2 are equal After if-Statement

				
					'''
__author__ = Ms. Samavi Salman
__copyright__= Copyright I 2020 Ms. Samavi Salman
__license__ = Public Domain
__version__ = 1.0
'''

try:
    print("Before If-Statement") 
    if 20 % 2 == 0:
        print("Statement 01 - Condition is True")
        print("Statement 02 – Number is even")
    else:
        print("Statement 01 - Condition is False")
        print("Statement 02 – Number is odd")
    print("After if-Statement")
except:
    print("Runtime Error")

Execution of Code (Dry Run)
Python Statement	Calculations	Variable(s)	Output
try:			Before If-Statement
print(“Before If-Statement”)			Before If-Statement
if 20 % 2 == 0:	Decision Making – Check Whether Condition is True or False 20 % 2 == 0 True (i.e., Statement(s) will be executed after if-Statement)		Before If-Statement
print(“Statement 01 – Condition is True”)	This Statement will be executed because Condition is True in above if-Statement (see Output Screen)		Before If-Statement Statement 01 – Condition is True
print(“Statement 02 – Number is Odd”)	This Statement will be executed because Condition is True in above if-Statement (see Output Screen)		Before If-Statement Statement 01 – Condition is True Statement 02 – Number is even
else:			Before If-Statement Statement 01 – Condition is True Statement 02 – Number is even
print(“Statement 01 – Condition is False”)	This Statement will not be executed because Condition is True in above if-Statement (see Output Screen)		Before If-Statement Statement 01 – Condition is True Statement 02 – Number is even
print(“Statement 02 – Number is odd”)	This Statement will not be executed because Condition is True in above if-Statement (see Output Screen)		Before If-Statement Statement 01 – Condition is True Statement 02 – Number is even
print(“After if-Statement”)			Before If-Statement Statement 01 – Condition is True Statement 02 – Number is even After if-Statement
except:			Before If-Statement Statement 01 – Condition is True Statement 02 – Number is even After if-Statement
print(“Runtime Error”)			Before If-Statement Statement 01 – Condition is True Statement 02 – Number is even After if-Statement

				
					'''
__author__ = Ms. Samavi Salman
__copyright__= Copyright I 2020 Ms. Samavi Salman
__license__ = Public Domain
__version__ = 1.0
'''

try:
    number1 = 10
    number2 = 4
    print("Before If-Statement") 
    exponent = number1 ** number2

    if exponent >= 1000:
        print("Statement 01 - Condition is True")
        print("Statement 02 – Exponent of", number1,"with", number2, "is greater than 1000")
    else:
        print("Statement 01 - Condition is False")
        print("Statement 02 – Exponent of", number1,"with", number2, "is less than 1000")
    print("After if-Statement")
except:
    print("Runtime Error")

Execution of Code (Dry Run)
Python Statement	Calculations	Variable(s)	Output
try:
number1 = 10
number2 = 4		number1 = 10
print(“Before If-Statement”)		number2 = 4	Before If-Statement
exponent = number1 number2**		number1 = 10 number2 = 4 exponent = 10000	Before If-Statement
if exponent >= 1000:	Decision Making – Check Whether Condition is True or False exponent >= 1000 + == + True (i.e., Statement(s) will be executed after if-Statement)	number1 = 10 number2 = 4 exponent = 10000	Before If-Statement
print(“Statement 01 – Condition is True”)	This Statement will be executed because Condition is True in above if-Statement (see Output Screen)	number1 = 10 number2 = 4 exponent = 10000	Before If-Statement Statement 01 – Condition is True
print(“Statement 02 – Exponent of”, number1,”with”, number2, “is greater than 1000”)	This Statement will be executed because Condition is True in above if-Statement (see Output Screen)	number1 = 10 number2 = 4 exponent = 10000	Before If-Statement Statement 01 – Condition is True Statement 02 – Exponent of 10 with 4 is greater than 1000
else:		number1 = 10 number2 = 4 exponent = 10000	Before If-Statement Statement 01 – Condition is True Statement 02 – Exponent of 10 with 4 is greater than 1000
print(“Statement 01 – Condition is False”)	This Statement will not be executed because Condition is True in above if-Statement (see Output Screen)	number1 = 10 number2 = 4 exponent = 10000	Before If-Statement Statement 01 – Condition is True Statement 02 – Exponent of 10 with 4 is greater than 1000
print(“Statement 02 – Exponent of”, number1,”with”, number2, “is less than 1000”)	This Statement will not be executed because Condition is True in above if-Statement (see Output Screen)	number1 = 10 number2 = 4 exponent = 10000	Before If-Statement Statement 01 – Condition is True Statement 02 – Exponent of 10 with 4 is greater than 1000
print(“After if-Statement”)		number1 = 10 number2 = 4 exponent = 10000	Before If-Statement Statement 01 – Condition is True Statement 02 – Exponent of 10 with 4 is greater than 1000 After if-Statement
except:		number1 = 10 number2 = 4 exponent = 10000	Before If-Statement Statement 01 – Condition is True Statement 02 – Exponent of 10 with 4 is greater than 1000 After if-Statement
print(“Runtime Error”)		number1 = 10 number2 = 4 exponent = 10000	Before If-Statement Statement 01 – Condition is True Statement 02 – Exponent of 10 with 4 is greater than 1000 After if-Statement

				
					'''
__author__ = Ms. Samavi Salman
__copyright__= Copyright I 2020 Ms. Samavi Salman
__license__ = Public Domain
__version__ = 1.0
'''
try:
    number = -10
    print("Before If-Statement") 
    if number < 0:
        print("Statement 01 - Condition is True")
        print("Statement 02 – ", number, "is a negative number")
    else:
        print("Statement 01 - Condition is False")
        print("Statement 02 – ", number, "is a positive number")
    print("After if-Statement")
except:
    print("Runtime Error")

Execution of Code (Dry Run)
Python Statement	Calculations	Variable(s)	Output
try:			Before If-Statement
number = -10		number = -10	Before If-Statement
print(“Before If-Statement”)		number = -10	Before If-Statement
if number < 0:	Decision Making – Check Whether Condition is True or False number < 0 -10 < 0 True (i.e., Statement(s) will be executed after if-Statement)	number = -10	Before If-Statement
print(“Statement 01 – Condition is True”)	This Statement will be executed because Condition is True in above if-Statement (see Output Screen)	number = -10	Before If-Statement Statement 01 – Condition is True
print(“Statement 02 – “, number, “is a negative number”)	This Statement will be executed because Condition is True in above if-Statement (see Output Screen)	number = -10	Before If-Statement Statement 01 – Condition is True Statement 02 – -10 is a negative number
else:		number = -10	Before If-Statement Statement 01 – Condition is True Statement 02 – -10 is a negative number
print(“Statement 01 – Condition is False”)	This Statement will not be executed because Condition is True in above if-Statement (see Output Screen)	number = -10	Before If-Statement Statement 01 – Condition is True Statement 02 – -10 is a negative number
print(“Statement 02 – “, number, “is a positive number”)	This Statement will not be executed because Condition is True in above if-Statement (see Output Screen)	number = -10	Before If-Statement Statement 01 – Condition is True Statement 02 – -10 is a negative number
print(“After if-Statement”)		number = -10	Before If-Statement Statement 01 – Condition is True Statement 02 – -10 is a negative number After if-Statement
except:		number = -10	Before If-Statement Statement 01 – Condition is True Statement 02 – -10 is a negative number After if-Statement
print(“Runtime Error”)		number = -10	Before If-Statement Statement 01 – Condition is True Statement 02 – -10 is a negative number After if-Statement

Completely and Correctly Understand a Task

Task Description

Write a Python Program which takes a Number as Input (from User) and makes a decision whether it’s a Positive Number or a Negative Number?

Sample Outputs

Sample Output 01

Enter an Integer Number: 100

100 is a Positive Number

Sample Output 02

Enter an Integer Number: -1.5

-1.5 is a Negative Number

Plan and Design Solution to the Task

Input-Processing-Output

Input
- Data
  - A Number
Instruction(s)
- Make a Decision – Whether the Number is Positive or Negative?
Output
- Display a Message (on the Output Screen) whether the Number is Positive or Negative?
Processing
- Use if-else Selection Structure for Decision Making – To check whether the Number is Positive or Negative?
  - Condition (To Check Whether the Number is Positive or Negative) – number >= 0.0
  - Use print() Function – To display the Message (on the Output Screen) whether the Number is Positive or Negative?

Pseudo Code

Step 1: Start

Step 2: Input – number

Step 3: if number is greater than or equal to 0.0

Print – Positive Number

else

Print – Negative Number

endif-else

Step 6: Stop

Flow Chart

Implementation in Python

Code

				
					'''
__author__   = Ms. Samavi Salman
__copyright__= Copyright I 2020 Ms. Samavi Salman
__license__  = Public Domain
__version__  = 1.0
'''

'''
The main purpose of this Program is to take an Integer Number as Input from User and check whether it is a Positive Number or a Negative Number?
'''

try:
    # Take an Integer Number as Input from User
    number = int(input("Enter an Integer Number: "))

    # Decision Making - Check whether Condition is True or False 
    if number >= 0.0:
        print(number, "is a Positive Number")
    else:
        print(number, " is a Negative Number ")

except ValueError:
    print("Sorry !!!. Invalid Input. Please enter Integer Number")

Execution of Code (Dry Run)
Python Statement	Calculations	Variable(s)	Output Screen
number = int(input(“Enter an Integer Number: “))		number = 100	Enter an Integer Number: 100
if number > 0:	Decision Making – Check Whether Condition is True or False number > 0 100 > 0 True (i.e., Statement(s) after if-Statement will be executed)	number = 100	Enter an Integer Number: 100
print(number, “is a Positive Number”)	This Statement will be executed because Condition is True in above if-Statement (see Output Screen)	number = 100	Enter an Integer Number: 100 100 is a Positive Number
else:	Decision Making – Check Whether Condition is True or False (Statement will be executed when Condition is False in the above if-Statement)	number = 100	Enter an Integer Number: 100 100 is a Positive Number
print(number, ” is a Negative Number “)	This Statement will not be executed because Condition is False in above if-Statement (see Output Screen)	number = 100	Enter an Integer Number:100 100 is a Positive Number
Output of Code
Enter an Integer Number: 100 100 is a Positive Number

Completely and Correctly Understand a Task

Task Description

Write a Python Program which takes Marks of Student as Input (from User) and makes a decision whether the Student passes or fails the course of Introduction to Python?

Sample Outputs

Sample Output 01

Enter marks in Introduction to Python course: 60

Congratulations!!! You passed the course

———————————————-

Sample Output 02

Enter marks in Introduction to Python course: 49

Sorry!!! You failed the course

———————————————-

Sample Output 03

Enter marks in Introduction to Python course: 49.99

Unfortunately!!! You failed the course

Plan and Design Solution to the Task

Input-Processing-Output

Input

- Data

- - Marks (Integer or Float)
- Instruction(s)
  - Make a Decision – Whether the Input Marks are greater than 50 or less than 50?
Output
- Display a Message (on the Output Screen) whether the Student passes the Course of Introduction to Python or not
Processing
- Use Conditions for Decision Making – To check whether the Student passes the Course of Introduction to Python or not
  - Condition for Pass– marks >= 50
  - Use print() Function – To display the Message (on the Output Screen) whether the Student passes the Course of Introduction to Python?

Pseudo Code

Step 1: Start

Step 2: Input – number (Integer Value)

Step 3: if marks are greater than or equal to 50.0

Print – Pass

else

Print – Fail

Endif-else

Step 6: Stop

Flow Chart

Implementation in Python

Code

				
					'''
__author__   = Ms. Samavi Salman
__copyright__= Copyright I 2020 Ms. Samavi Salman
__license__  = Public Domain
__version__  = 1.0
'''

'''
The main purpose of this Program is to take an Integer Number as Input from User and check whether it’s an Even Number or an Odd Number?
'''

try:
    # Take an Integer Number as Input from User
    marks = float(input("Enter Marks in Course: "))
    # Decision Making - Check whether Condition is True or False 

    if marks >= 50.0:
        print("Congratulations!!! You passed the course")

    else:
        print("Unfortunately!!! You failed the course")

except ValueError:
    print("Sorry !!!. Invalid Input. Please enter Integer Number")

Execution of Code (Dry Run)
Python Statement	Calculations	Variable(s)	Output Screen
marks = float(input(“Enter Marks in Course: “))		marks = 49.9	Enter Marks in Course: 49.9
if marks >= 50:	Decision Making – Check Whether Condition is True or False marks >= 50 49.9 >= 50 False (i.e., Statement(s) after if-Statement will not be executed)		Enter Marks in Course: 49.9
print(“Congratulations!!! You passed the course”)	This Statement will not be executed because Condition is False in above if-Statement (see Output Screen)		Enter Marks in Course: 49.9
else:	Decision Making – Check Whether Condition is True or False (Statement will be executed when Condition is False in the above if-Statement)		Enter Marks in Course: 49.9
print(“Unfortunately!!! You failed the course”)	This Statement will be executed because Condition is True in above if-Statement (see Output Screen)		Enter Marks in Course: 49.9 Unfortunately!!! You failed the course
Output of Code
Enter marks in Introduction to Python course: 49.99 Unfortunately!!! You failed the course

Completely and Correctly Understand a Task

Task Description

Write a Python Program which takes an Integer Number as Input (from User) and makes a decision whether it’s an Even Number or an Odd Number?

Sample Outputs

Sample Output 01

Enter an Integer Number: 5

5 is an Odd Number

———————————–

Sample Output 02

Enter an Integer Number: 12

12 is an Odd Number

———————————–

Sample Output 03

Enter an Integer Number: 500

500 is an Even Number

Plan and Design Solution to the Task

Input-Processing-Output

Input
- Data
  - An Integer Number
Instruction(s)
- Make a Decision – Whether the Input Integer Number is Odd or Even?
Output
- Display a Message (on the Output Screen) whether the Input Integer Number is an Even Number or Odd Number
Processing
- Use Conditions for Decision Making – To check whether the Integer Number is Odd or Even?
  - Condition for Even Number – number % 2 == 0
  - Use print() Function – To display the Message (on the Output Screen) whether the Integer Number is Even or Odd?

Pseudo Code

Step 1: Start

Step 2: Input – number (Integer Value)

Step 3: if Modulus of number with 2 is equal to 0

Print – Even Number

Step 5: else

Print – Odd Number

endif

Step 6: Stop

Flow Chart

Implementation in Python

Code

				
					'''
__author__   = Ms. Samavi Salman
__copyright__= Copyright I 2020 Ms. Samavi Salman
__license__  = Public Domain
__version__  = 1.0
'''
'''
The main purpose of this Program is to take an Integer Number as Input from User and check whether it is an Even Number or an Odd Number?
'''
try:
    # Take an Integer Number as Input from User
    number = int(input("Enter an Integer Number: "))

    # Decision Making - Check whether Condition is True or False 
    if number % 2 == 0:
        print(number, "is an Even Number")
    else:
        print(number, "is an Odd Number")

except ValueError:
    print("Sorry !!!. Invalid Input. Please enter Integer Number")

Execution of Code (Dry Run)
Python Statement	Calculations	Variable(s)	Output Screen
number = int(input(“Enter an Integer Number: “))		number = 7	Enter an Integer Number: 7
if number % 2 == 0:	Decision Making – Check Whether Condition is True or False number % 2 == 0 7 % 2 == 0 1 == 0 False (i.e., Statement(s) after if-Statement will not be executed)	number = 7	Enter an Integer Number: 7
print(number, “is an Even Number”)	This Statement will not be executed because Condition is False in above if-Statement (see Output Screen)	number = 7	Enter an Integer Number: 7
else:	Decision Making – Check Whether Condition is True or False (Statement will be executed when Condition is False in the above if-Statement)	number = 7	Enter an Integer Number: 7
print(number, “is an Odd Number”)	This Statement will be executed because Condition is True in above if-Statement (see Output Screen)	number = 7	Enter an Integer Number:7 7 is an Odd Number
Output of Code
Enter an Integer Number: 7 7 is an Odd Number

Completely and Correctly Understand a Task

Task Description

Calculate the Temperature of a person using Thermometer. Write a Python Program which takes a Number as Input (from User) and makes a decision: (1) Number is Positive (2) Number is Negative?

Sample Outputs

Sample Output 01

Enter a Number: 50.45

50.45 is a Positive Number

———————————————-

Sample Output 02

Enter a Number: 0

0 is a Positive Number

———————————————-

Sample Output 03

Enter a Number: -45.76

-45.76 is a Negative Number

———————————————-

Sample Output 04

Enter a Number: -1000

-1000 is a Negative Number

———————————————-

Sample Output 05

Enter a Number: courage

Sorry !!!. Invalid Input. Please enter Integer / Float Number

Plan and Design Solution to the Task

Input-Processing-Output

Input
- Data
  - A Number
Instruction(s)
- Make a Decision – Whether the Number is Positive or Negative?
Output
- Display a Message (on the Output Screen) whether the Number is Positive or Negative?
Processing
- Use if-else Selection Structure for Decision Making – To check whether the Number is Positive or Negative?
  - Condition (To Check Whether the Number is Positive or Negative) – number >= 0.0
  - Use print() Function – To display the Message (on the Output Screen) whether the Number is Positive or Negative?

Pseudo Code

Step 1: Start

Step 2: Input – number

Step 3: if number is greater than or equal to 0.0

Print – Positive Number

else

Print – Negative Number

endif

Step 6: Stop

Flow Chart

Implementation in Python

Code

				
					'''
__author__   = Ms. Samavi Salman
__copyright__= Copyright I 2020 Ms. Samavi Salman
__license__  = Public Domain
__version__  = 1.0
'''

'''
The main purpose of this Program is to take a Number (Integer / Float) as Input from User and check whether it’s a Positive Number or a Negative Number?
'''

try:
    # Take a Number (Integer / Float) as Input from User
    number = float(input("Enter an Integer Number: "))

    # Decision Making - Check whether Condition is True or False 
    if number >= 0.0:
        print(number, "is a Positive Number")
    else:
        print(number, " is a Negative Number ")

except ValueError:
    print("Sorry !!!. Invalid Input. Please enter Integer / Float Number")

Execution of Code (Dry Run)
Python Statement	Calculations	Variable(s)	Output Screen
try:
number = int(input(“Enter an Integer Number: “))		number = 100	Enter an Integer Number: 100
if number > 0:	Decision Making – Check Whether Condition is True or False number > 0 100 > 0 True (i.e., Statement(s) will be executed after if-Statement)	number = 100	Enter an Integer Number: 100
print(number, “is a Positive Number”)	This Statement will be executed because Condition is True in above if-Statement (see Output Screen)	number = 100	Enter an Integer Number: 100 100 is a Positive Number
else:	Decision Making – Check Whether Condition is True or False (Statement will be executed when Condition is False in the above if-Statement)	number = 100	Enter an Integer Number: 100 100 is a Positive Number
print(number, ” is a Negative Number “)	This Statement will not be executed because Condition is False in above if-Statement (see Output Screen)	number = 100	Enter an Integer Number:100 100 is a Positive Number
except ValueError:		number = 100	Enter an Integer Number:100 100 is a Positive Number
print(“Sorry !!!. Invalid Input. Please enter Integer / Float Number”)		number = 100	Enter an Integer Number:100 100 is a Positive Number
Output of Code
Enter an Integer Number: 100 100 is a Positive Number

Completely and Correctly Understand a Task

Task Description

Calculate the Temperature of a person using Thermometer. Write a Python Program which takes a Number as Input (from User) and makes a decision: (1) Number is Positive (2) Number is Negative?

Sample Outputs

Sample Output 01

Enter a Number: 50.45

50.45 is a Positive Number

———————————————-

Sample Output 02

Enter a Number: 0

0 is a Positive Number

———————————————-

Sample Output 03

Enter a Number: -45.76

-45.76 is a Negative Number

———————————————-

Sample Output 04

Enter a Number: -1000

-1000 is a Negative Number

———————————————-

Sample Output 05

Enter a Number: courage

Sorry !!!. Invalid Input. Please enter Integer / Float Number

Plan and Design Solution to the Task

Input-Processing-Output

Input

- Data

- - A Number
- Instruction(s)
  - Make a Decision – Whether the Number is Positive or Negative?
Output
- Display a Message (on the Output Screen) whether the Number is Positive or Negative?
Processing
- Use if-else Selection Structure for Decision Making – To check whether the Number is Positive or Negative?
  - Condition (To Check Whether the Number is Positive or Negative) – number >= 0.0
  - Use print() Function – To display the Message (on the Output Screen) whether the Number is Positive or Negative?

Pseudo Code

Step 1: Start

Step 2: Input – number

Step 3: if number is greater than or equal to 0.0

Print – Positive Number

else

Print – Negative Number

endif

Step 6: Stop

Flow Chart

Implementation in Python

Code

				
					'''
__author__   = Ms. Samavi Salman
__copyright__= Copyright I 2020 Ms. Samavi Salman
__license__  = Public Domain
__version__  = 1.0
'''

'''
The main purpose of this Program is to take a Number (Integer / Float) as Input from User and check whether it’s a Positive Number or a Negative Number?
'''

try:
    # Take a Number (Integer / Float) as Input from User
    number = float(input("Enter an Integer Number: "))

    # Decision Making - Check whether Condition is True or False 
    if number >= 0.0:
        print(number, "is a Positive Number")

    else:
        print(number, " is a Negative Number ")

except ValueError:
    print("Sorry !!!. Invalid Input. Please enter Integer / Float Number")

Execution of Code (Dry Run)
Python Statement	Calculations	Variable(s)	Output Screen
try:
number = int(input(“Enter an Integer Number: “))		number = 100	Enter an Integer Number: 100
if number > 0:	Decision Making – Check Whether Condition is True or False number > 0 100 > 0 True (i.e., Statement(s) will be executed after if-Statement)	number = 100	Enter an Integer Number: 100
print(number, “is a Positive Number”)	This Statement will be executed because Condition is True in above if-Statement (see Output Screen)	number = 100	Enter an Integer Number: 100 100 is a Positive Number
else:	Decision Making – Check Whether Condition is True or False (Statement will be executed when Condition is False in the above if-Statement)	number = 100	Enter an Integer Number: 100 100 is a Positive Number
print(number, ” is a Negative Number “)	This Statement will not be executed because Condition is False in above if-Statement (see Output Screen)	number = 100	Enter an Integer Number:100 100 is a Positive Number
except ValueError:		number = 100	Enter an Integer Number:100 100 is a Positive Number
print(“Sorry !!!. Invalid Input. Please enter Integer / Float Number”)		number = 100	Enter an Integer Number:100 100 is a Positive Number
Output of Code
Enter an Integer Number: 100 100 is a Positive Number

Completely and Correctly Understand a Task

Task Description

A Teacher wants to mark the status of Students as Pass or Fail. Write a Python Program which takes Marks of a Student in a Course as Input (from User) and makes a decision: (1) Student Passed the Course (2) Student Failed in the Course?

Sample Outputs

Sample Output 01

Enter Marks in Course: 89.5

You Passed the Course of Introduction to Python

———————————————————————

Sample Output 02

Enter Marks in Course: 49.9

You Failed the Course of Introduction to Python

———————————————————————

Sample Output 03

Enter Marks in Course: 50

You Passed the Course of Introduction to Python

———————————————————————

Sample Output 04

Enter Marks in Course: 45

You Failed the Course of Introduction to Python

———————————————————————

Sample Output 05

Enter Marks in Course: passion

Sorry !!!. Invalid Input. Please enter Integer / Float Number

Plan and Design Solution to the Task

Input-Processing-Output

Input

- Data

- - Marks (of a Student in a Course)
- Instruction(s)
  - Make a Decision – Whether the Student Passed the Course or Not?
Output
- Display a Message (on the Output Screen) whether the Student passed the Course or not?
Processing
- Use Conditions for Decision Making – To check whether the Student passed / failed the Course
  - Condition (To Check Whether Student Passed the Course or Not) – marks >= 50.0
  - Use print() Function – To display the Message (on the Output Screen) whether the Student passed/ failed the Course

Pseudo Code

Step 1: Start

Step 2: Input – marks (Integer / Float)

Step 3: if marks are greater than or equal to 50.0

Print – Pass

else

Print – Fail

Endif

Step 6: Stop

Flow Chart

Implementation in Python

Code

				
					'''
__author__   = Ms. Samavi Salman
__copyright__= Copyright I 2020 Ms. Samavi Salman
__license__  = Public Domain
__version__  = 1.0
'''
'''
The main purpose of this Program is to take Marks (Integer / Float) as Input from User and check whether the Student passed/ failed the Course?
'''

try:
    # Take a Number (Integer / Float) as Input from User
    marks = float(input("Enter Marks in Course: "))

    # Decision Making - Check whether Condition is True or False 
    if marks >= 50.0:
        print("You Passed the Course of Introduction to Python")
    else:
        print("You Failed the Course of Introduction to Python")

except ValueError:
    print("Sorry !!!. Invalid Input. Please enter Integer / Float Number")

Execution of Code (Dry Run)
Python Statement	Calculations	Variable(s)	Output Screen
try:
marks = float(input(“Enter Marks in Course: “))		marks = 70	Enter Marks in Course: 70
if marks >= 50.0:	Decision Making – Check Whether Condition is True or False marks >= 50 70 >= 50 True (i.e., Statement(s) will be executed after if-Statement)	marks = 70	Enter Marks in Course: 70
print(“You Passed the Course of Introduction to Python”)	This Statement will be executed because Condition is True in above if-Statement (see Output Screen)	marks = 70	Enter Marks in Course: 70 You Passed the Course of Introduction to Python
else:	Decision Making – Check Whether Condition is True or False (Statement will be executed when Condition is False in the above if-Statement)	marks = 70	Enter Marks in Course: 70 You Passed the Course of Introduction to Python
print(“You Failed the Course of Introduction to Python”)	This Statement will not be executed because Condition is False in above if-Statement (see Output Screen)	marks = 70	Enter Marks in Course: 70 You Passed the Course of Introduction to Python
except ValueError:		marks = 70	Enter Marks in Course: 70 You Passed the Course of Introduction to Python
print(“Sorry !!!. Invalid Input. Please enter Integer / Float Number”)		marks = 70	Enter Marks in Course: 70 You Passed the Course of Introduction to Python
Output of Code
Enter Marks in Course: 70 Congratulations!!! You passed the course

Completely and Correctly Understand a Task

Task Description

Count the number of Students in the classroom. After counting, identify if the total is even or odd. Write a Python Program which takes an Integer Number as Input (from User) and makes a decision whether it’s an Even Number or an Odd Number?

Sample Outputs

Sample Output 01

Enter an Integer Number: 5

5 is an Odd Number

——————————————

Sample Output 02

Enter an Integer Number: 100

100 is an Even Number

——————————————

Sample Output 03

Enter an Integer Number: 10.25

Sorry Invalid Input!!! Please Enter an Integer Number

——————————————

Sample Output 04

Enter an Integer Number: honest

Sorry Invalid Input!!! Please Enter an Integer Number

Plan and Design Solution to the Task

Input-Processing-Output

Input

- Data

- - An Integer Number
- Instruction(s)
  - Make a Decision – Whether the Input Integer Number is Odd or Even?
Output
- Display a Message (on the Output Screen) whether the Input Integer Number is an Even Number or Odd Number
Processing
- Use Conditions for Decision Making – To check whether the Integer Number is Odd or Even?
  - Condition (To check whether number is Even Number or Odd Number) – number % 2 == 0
  - Use print() Function – To display the Message (on the Output Screen) whether the Integer Number is Even or Odd?

Pseudo Code

Step 1: Start

Step 2: Input – number (Integer Value)

Step 3: if Modulus of number with 2 is equal to 0

Print – Even Number

else

Print – Odd Number

endif

Step 4: Stop

Flow Chart

Implementation in Python

Code

				
					'''
__author__   = Ms. Samavi Salman
__copyright__= Copyright I 2020 Ms. Samavi Salman
__license__  = Public Domain
__version__  = 1.0
'''

'''
The main purpose of this Program is to take an Integer Number as Input from User and check whether it is an Even Number or an Odd Number?
'''

try:
    # Take an Integer Number as Input from User
    number = int(input("Enter an Integer Number: "))

    # Decision Making - Check whether Condition is True or False 
    if number % 2 == 0:
        print(number, "is an Even Number")
    else:
        print(number, "is an Odd Number")

except ValueError:
    print("Sorry !!!. Invalid Input. Please enter Integer Number")

Execution of Code (Dry Run)
Python Statement	Calculations	Variable(s)	Output Screen
try:
number = int(input(“Enter an Integer Number: “))		number = 7	Enter an Integer Number: 7
if number % 2 == 0:	Decision Making – Check Whether Condition is True or False number % 2 == 0 7 % 2 == 0 1 == 0 False (i.e., Statement(s) will be executed after if-Statement)	number = 7	Enter an Integer Number: 7
print(number, “is an Even Number”)	This Statement will not be executed because Condition is False in above if-Statement (see Output Screen)	number = 7	Enter an Integer Number: 7
else:	Decision Making – Check Whether Condition is True or False (Statement will be executed when Condition is False in the above if-Statement)	number = 7	Enter an Integer Number: 7
print(number, “is an Odd Number”)	This Statement will be executed because Condition is True in above if-Statement (see Output Screen)	number = 7	Enter an Integer Number:7 7 is an Odd Number
except ValueError:		number = 7	Enter an Integer Number:7 7 is an Odd Number
print(“Sorry !!!. Invalid Input. Please enter Integer Number”)		number = 7	Enter an Integer Number:7 7 is an Odd Number
Output of Code
Enter an Integer Number: 7 7 is an Odd Number

TODO and Your Turn

Todo Tasks

Your Turn Tasks

Todo Tasks

Your Turn Tasks

Ilm o Irfan

Introduction to Python

Table of Contents

Chapter 17 - if-else Selection Structure

IF - ELSE Statement in Python

Execution of Code (Dry Run)

Python Statement

Calculations

Variable(s)

Output

Execution of Code (Dry Run)

Python Statement

Calculations

Variable(s)

Output

Execution of Code (Dry Run)

Python Statement

Calculations

Variable(s)

Output

Execution of Code (Dry Run)

Python Statement

Calculations

Variable(s)

Output

Execution of Code (Dry Run)

Python Statement

Calculations

Variable(s)

Output

Execution of Code (Dry Run)

Python Statement

Calculations

Variable(s)

Output

Completely and Correctly Understand a Task

Task Description

Sample Outputs

Plan and Design Solution to the Task

Input-Processing-Output

Pseudo Code

Flow Chart

Implementation in Python

Code

Execution of Code (Dry Run)

Python Statement

Calculations

Variable(s)

Output Screen

Output of Code

Completely and Correctly Understand a Task

Task Description

Sample Outputs

Plan and Design Solution to the Task

Input-Processing-Output

Pseudo Code

Flow Chart

Implementation in Python

Code

Execution of Code (Dry Run)

Python Statement

Calculations

Variable(s)

Output Screen

Output of Code

Completely and Correctly Understand a Task

Task Description

Sample Outputs

Plan and Design Solution to the Task

Input-Processing-Output

Pseudo Code

Flow Chart

Implementation in Python

Code

Execution of Code (Dry Run)

Python Statement

Calculations

Variable(s)

Output Screen

Output of Code