Decision Making and Loops in Python

Decision Making:

Decision making evaluates the multiple conditions that will produce TRUE or FALSE as an output. Following figure shows the typical structure of decision making:

Python programming language having following types of decision making statements,

1.      If statement
2.    If … else statement
3.    Nested if statement

1.        If statement :

It is used for decision making and run the body of the code when if statement is true.

Syntax:

            If expression:

                        statement(s)

Example:

            a=10

            b=8

if a>b:

            print(“a is greater than b”)

 2.      If … else statement:

In this type else statement is combined with an if statement. It is mainly used to execute Boolean conditions like if for true and else for false.

Syntax:

if expression:

            statement(s)

else:

            statement(s)

Example:

mark = int(input("Enter the mark of student:"))

if mark >= 40:

    print("Student is passed")

else:

    print("Student is failed")

Above code produce following output:

Enter the marks of student: 38

Student is failed

3.      Nested if statement:

When there are more than two conditions are presents, in that situation nested if statements are used.

Syntax:

if expression1:
    statement(s)
    if expression2:
      statement(s)
    elif expression3:
      statement(s)
    else
      statement(s)
elif expression4:
    statement(s)
else:
    statement(s)

Example:

if 1 = = 2:

    print('first')

elif 3 = = 3:

    print('middle')

else:

    print('Last')

Above code produce following output:

middle

Loops in Python:

In Python there are following types of loops are mainly used:

1.       For loop
2. While loop

 1. For loop: It executes a sequence of statements multiple times up to the given condition satisfied.

For example:

seq = [1,2,3,4,5]

for item in seq:

    print(item)

It displays following output:

1

2

3

4

5

2. While loop: It repeats a given one or more statements while a given condition becomes true.

Syntax:

while expression:
statement(s)

Example:

i = 1

while i < 4:

    print('i is: {}'.format(i))

    i = i+1

It displays following output:

                    i is: 1

                    i is: 2

                    i is: 3