This document summarizes key concepts from lectures 9-11 on conditionals and recursion in Python programming. It discusses logical operators, relational operators, boolean expressions, floor division, modulus, conditional execution using if/else statements, chained and nested conditionals. Recursion is defined as a function calling itself and examples of valid and infinite recursion are provided. The document also covers taking keyboard input in Python using the input function.

1. Python Programming
Unit – II (Part II)
(Lecture 11)
Conditionals and Recursion
Recursion Infinite Recursion Keyboard input

2. Python Programming
Unit – II (Part II)
(Lecture 9)
Conditionals and Recursion

3. Syllabus
Lecture 9
Lecture 10
Lecture 11
Floor division and
modulus
Boolean expressions
Logical operators
Conditional
execution
Alternative
execution
Chained
conditionals
Nested
conditionals
Recursion
Infinite Recursion
Keyboard input

4. Syllabus
Lecture 9
Floor division and
modulus
Boolean expressions
Logical operators

5. • There are three logical
operators:
1. and
2. or
3. not
Relational operators:
• A = = B(Equal to)
• A! = B (Not equal to)
• A > B (Greater than)
• A < B (Less than)
• A > = B (Greater than or equal to)
• A < = B (Less than or equal to)
A Boolean expression is either
true or false.
• Ex: A = 5, B = 5, C = 6
• A = = B returns True
• A = = C returns False
Floor division:
• Digits after the decimal point
are removed.
• Symbol for Floor division: //
• Ex: 9 / 2 is 4.5 (Division)
9 // 2 is 4 (Floor division)
Modulus:
• Returns the remainder value
• Symbol for Modulus: %
• Ex: 9 % 2 is 1
Floor division and
modulus
Boolean expressions Logical operators

6. • There are three logical
operators:
1. and
2. or
3. not
Relational operators:
• A = = B(Equal to)
• A! = B (Not equal to)
• A > B (Greater than)
• A < B (Less than)
• A > = B (Greater than or equal to)
• A < = B (Less than or equal to)
A Boolean expression is either
true or false.
• Ex: A = 5, B = 5, C = 6
• A = = B returns True
• A = = C returns False
Floor division:
• Digits after the decimal point
are removed.
• Symbol for Floor division: //
• Ex: 9 / 2 is 4.5 (Division)
9 // 2 is 4 (Floor division)
Modulus:
• Returns the remainder value
• Symbol for Modulus: %
• Ex: 9 % 2 is 1
Floor division and
modulus
Boolean expressions Logical operators

7. Python Programming
Unit – II (Part II)
(Lecture 10)
Conditionals and Recursion

8. Syllabus
Lecture 9
Lecture 10
Lecture 11
Floor division and
modulus
Boolean expressions
Logical operators
Conditional
execution
Alternative
execution
Chained
conditionals
Nested
conditionals
Recursion
Infinite Recursion
Keyboard input

9. Syllabus
Lecture 10
Conditional
execution
Alternative
execution
Chained
conditionals
Nested
conditionals

10. Conditional
execution
Alternative
execution
Chained
conditionals
Nested
conditionals
• Conditions change
the flow of program
execution
• if statement is used
in conditions
Syntax:
if condition:
statement 1
…
• Two possibilities
(else is used)
Syntax:
if condition:
statement 1
…
else:
statement 2
…
• More than two
possibilities.
• elif is used.
Syntax:
if condition:
statement 1
elif condition:
statement 2
elif condition:
statement 3
else:
statement 4
• Another Condition
in one condition
Syntax:
if condition1:
if condition2:
statement 1
else:
statement 2
else:
statement 3
Conditionals

11. Conditional
execution
Alternative
execution
Chained
conditionals
Nested
conditionals
• Conditions change
the flow of program
execution
• if statement is used
in conditions
Syntax:
if condition:
statement 1
…
• Two possibilities
(else is used)
Syntax:
if condition:
statement 1
…
else:
statement 2
…
• More than two
possibilities.
• elif is used.
Syntax:
if condition:
statement 1
elif condition:
statement 2
elif condition:
statement 3
else:
statement 4
• Another Condition
in one condition
Syntax:
if condition1:
if condition2:
statement 1
else:
statement 2
else:
statement 3

12. Python Programming
Unit – II (Part II)
(Lecture 11)
Conditionals and Recursion

13. • There are three logical
operators:
1. and
2. or
3. not
Relational operators:
• A = = B(Equal to)
• A! = B (Not equal to)
• A > B (Greater than)
• A < B (Less than)
• A > = B (Greater than or equal to)
• A < = B (Less than or equal to)
A Boolean expression is either
true or false.
• Ex: A = 5, B = 5, C = 6
• A = = B returns True
• A = = C returns False
Floor division:
• Digits after the decimal point
are removed.
• Symbol for Floor division: //
• Ex: 9 / 2 is 4.5 (Division)
9 // 2 is 4 (Floor division)
Modulus:
• Returns the remainder value
• Symbol for Modulus: %
• Ex: 9 % 2 is 1
Floor division and
modulus
Boolean expressions Logical operators

14. Conditional
execution
Alternative
execution
Chained
conditionals
Nested
conditionals
• Conditions change
the flow of program
execution
• if statement is used
in conditions
Syntax:
if condition:
statement 1
…
• Two possibilities
(else is used)
Syntax:
if condition:
statement 1
…
else:
statement 2
…
• More than two
possibilities.
• elif is used.
Syntax:
if condition:
statement 1
elif condition:
statement 2
elif condition:
statement 3
else:
statement 4
• Another Condition
in one condition
Syntax:
if condition1:
if condition2:
statement 1
else:
statement 2
else:
statement 3

15. Syllabus
Lecture 9
Lecture 10
Lecture 11
Floor division and
modulus
Boolean expressions
Logical operators
Conditional
execution
Alternative
execution
Chained
conditionals
Nested
conditionals
Recursion
Infinite Recursion
Keyboard input

16. Lecture 11
Recursion
Infinite Recursion
Keyboard input
Recursion

17. Recursion
• Function to call
itself
Ex:
def countdown(n):
if n < 0:
print (“Blast”)
else:
print (n)
n = n - 1
countdown(n)
Countdown(n)
n
4
If
n < 0
False
Print(n)
n = n-1
Output:
4

18. Recursion
• Function to call
itself
Ex:
def countdown(n):
if n < 0:
print (“Blast”)
else:
print (n)
n = n - 1
countdown(n)
Countdown(n)
n
3
If
n < 0
False
Print(n)
n = n-1
Call count down
Output:
4
3

19. Recursion
• Function to call
itself
Ex:
def countdown(n):
if n < 0:
print (“Blast”)
else:
print (n)
n = n - 1
countdown(n)
Countdown(n)
n
2
If
n < 0
False
Print(n)
n = n-1
Call count down
Output:
4
3
2

20. Recursion
• Function to call
itself
Ex:
def countdown(n):
if n < 0:
print (“Blast”)
else:
print (n)
n = n - 1
countdown(n)
Countdown(n)
n
1
If
n < 0
False
Print(n)
n = n-1
Call count down
Output:
4
3
2
1

21. Recursion
• Function to call
itself
Ex:
def countdown(n):
if n < 0:
print (“Blast”)
else:
print (n)
n = n - 1
countdown(n)
Countdown(n)
n
0
If
n < 0
False
Print(n)
n = n-1
Call count down
Output:
4
3
2
1
0

22. Recursion
• Function to call
itself
Ex:
def countdown(n):
if n < 0:
print (“Blast”)
else:
print (n)
n = n - 1
countdown(n)
Countdown(n)
n
-1
If
n < 0
False
Print(n)
n = n-1
Call count down
Output:
4
3
2
1
0
Blast
Print(“Blast”)
True

23. Recursion
Lecture 11
Recursion
Infinite Recursion
Keyboard input

24. Countdown(n)
n
4
If
n < 0
False
Print(n)
n = n+1
Output:
4
Infinite Recursion
• Making recursive
calls forever
• The program never
terminates.
Ex:
def countdown(n):
if n < 0:
print (“Blast”)
else:
print (n)
n=n+1
countdown(n)

25. Countdown(n)
n
5
If
n < 0
False
Print(n)
n = n+1
Call count down
Output:
4
5
Infinite Recursion
• Making recursive
calls forever
• The program never
terminates.
Ex:
def countdown(n):
if n < 0:
print (“Blast”)
else:
print (n)
countdown(n+1)

26. Countdown(n)
n
6
If
n < 0
False
Print(n)
n = n+1
Call count down
Output:
4
5
6
Infinite Recursion
• Making recursive
calls forever
• The program never
terminates.
Ex:
def countdown(n):
if n < 0:
print (“Blast”)
else:
print (n)
countdown(n+1)

27. Countdown(n)
n
7
If
n < 0
False
Print(n)
n = n+1
Call count down
Output:
4
5
6
7
Infinite Recursion
• Making recursive
calls forever
• The program never
terminates.
Ex:
def countdown(n):
if n < 0:
print (“Blast”)
else:
print (n)
countdown(n+1)

28. Countdown(n)
n
8
If
n < 0
False
Print(n)
n = n+1
Call count down
Output:
4
5
6
7
8
Infinite Recursion
• Making recursive
calls forever
• The program never
terminates.
Ex:
def countdown(n):
if n < 0:
print (“Blast”)
else:
print (n)
countdown(n+1)

29. Countdown(n)
n
9
If
n < 0
False
Print(n)
n = n+1
Call count down
Output:
4
5
6
7
8
Infinite recursion
Infinite Recursion
• Making recursive
calls forever
• The program never
terminates.
Ex:
def countdown(n):
if n < 0:
print (“Blast”)
else:
print (n)
countdown(n+1)

30. Recursion
Lecture 11
Recursion
Infinite Recursion
Keyboard input

31. Keyboard input
• Accept input
from the user
with keyboard.
• input function
is used
A = 5
B = 6
print( A + B ) is 11
Here A & B variables has fixed values (given in
the program)
A = int(input("enter a value:"))
B = int(input("enter b value:"))
print( A + B)
Here A & B variables has no fixed values (given
in runtime)