Conditional and control statement

CONDITIONAL STATEMENTS
and
CONTROL STATEMENTS
1
Prepared by
V.Kumararaja, AP/IT
S.Thanga Prasath, AP/CSE
Er.Perumal Manimekalai Colleg of Engineering,
Hosur

CONDITIONAL STATEMENTS (Decision Making)
The basic decision statements in computer is
selection structure.
The decision is described to computer as a
conditional statement that can be answered
True or False.
Python language provide the following
conditional (Decision making) statements.
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if statement
if...else statement
if...elif...else staement
Nested if..else statement

The if statement
The if statement is a decision making statement.
It is used to control the flow of execution of the
statements and also used to test logically
whether the condition is true or false.
Syntax
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if test expression:
statement(s)

Example program
i=int(input(“Enter the number:”))
If (i<=10):
print(“ condition is true”)
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OUTPUT
Enter the number: 9
Condition is true

If … else statement
The if…else statement is called alternative
execution, in which there are two possibilities
and the condition determines wich one gets
executed.
Syntax
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if test expression:
Body of if
else:
Body of else

Write a program to check if a number is Odd or Even
num = int(input(“Enter the number:”))
if (num % 2)== 0:
print (“Given number is Even”)
else:
print(“ Given number is Odd”)
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OUTPUT
Enter the number: 9
Given number is Odd

elif Statements
 elif – is a keyword used in Python in
replacement of else if to place another condition
in the program. This is called chained conditional.
 Chained conditions allows than two
possibilities and need more than two branches.
SYNTAX
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if expression:
Body of if
elif expression:
Body of elif
else:
Body of else

Figure – elif condition Flowchart
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Example: largest among three numbers
a = int(input(“Enter 1st number:”))
b= int(input(“Enter 2nd number:”))
c= int(input(“Enter 3rd number:”))
if (a > b) and (a > c):
print("a is greater")
elif (b < a) and (b < c):
print(“b is greater")
else:
print(“c is greater")
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OUTPUT
Enter 1st number:10
Enter 2nd number:25
Enter 3rd number:15
B is greater

Nested if … else Statements
 We can write an entire if… else statement in
another if… else statement called nesting, and the
statement is called nested if.
 In a nested if construct, you can have an if … elif
… else construct inside an if … elif.. Else construct.
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Syntax
if expression1:
statement(s)
if expression2:
statement(s)
elif expression3:
statement(s)
else:
statement(s)
.
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• Example program
n = int(input(“Enter number:”))
If (n<=15):
if (n == 10):
print(‘play cricket’)
else:
print(‘play kabadi’)
Else:
print(‘Don’t play game’)
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OUTPUT
Enter number : 10
Play cricket

CONTROL STATEMENT (Looping Statement)
Program statement are executed sequentially
one after another. In some situations, a block
of code needs of times.
These are repetitive program codes, the
computers have to perform to complete tasks.
The following are the loop structures available
in python.
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while statement
for loop statement
Nested loop staement

While loop statement
 A while loop statement in Python
programming language repeatedly executes a
target statement as long as a given condition is
true.
Syntax of while loop
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while expression:
statement(s)

Write a program to find sum of number
num = int(input("Enter a number: "))
sum = 0
while(num > 0):
sum = sum+num
num = num-1
print("The sum is",sum)
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OUTPUT
Enter a number: 10
The sum is 55

Using else statement with while loops
 Python supports t have an else statement associated
with a loop statement.
 If the else statement is used with a while loop, the
else statement is executed when the condition false.
Program to illustrate the else in while loop
counter = 0
while counter < 3:
print("Inside loop")
counter = counter + 1
else:
print(“Outside loop")
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OUTPUT
Inside loop
Inside loop
Inside loop
Outside loop

For loop statement
The for loop is another repetitive control
structure, and is used to execute a set of
instructions repeatedly, until the condition
becomes false.
The for loop in Python is used to iterate over a
sequence (list, tuple, string) or other iterable
objects. Iterating over a sequence is called
traversal.
Syntax
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for val in sequence:
Body of for loop

For loop flow chart
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Addition of number using for loop
numbers = [6, 5, 3, 8, 4, 2, 5, 4]
sum1 = 0
for val in numbers:
sum1 = sum1+val
print("The sum is", sum1)
OUTPUT
The sum is 37

for Loop and for Loop with else
EX-01:
genre = ['pop', 'rock', 'jazz']
for i in range(len(genre)):
print("I like", genre[i])
EX-02:
genre = ['pop', 'rock', 'jazz']
for i in range(len(genre)):
print("I like", genre[i])
else:
print("No items left.")
OUTPUT
I like pop
I like rock
I like jazz
OUTPUT
I like pop
I like rock
I like jazz
No items left.

Conditional and control statement

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