To evaluate multiple conditions we use nested if statement. The general form is
Syntax
if test condition1:
if test condition2:
statement1
else:
statement2
else:
statement3
From the above syntax if the condition1 is true control transfers to condition2 when it is true statement 1 executes, oterwise statement 2 will be executed.If the condition1 itself false the control will be transferred to else part and statement3 will be executed.
If statement: If statement evaluates the test condition and will execute statement-block only if the condition is True. If the condition is False, the statement-block is not executed and control is transferred to next statements. The group of statements which has to be executed when the condition is true are written in statements-block. Statement-block may be a single statement or group of statements with proper indent.
Flow chart :
Ex: Python program to check whether the given number is positive or not
num = float(input("Enter a number: "))
if num > 0:
print("Positive number")
print("Simple if")
Output:
Enter a number 5
Positive number
Simple if
If –else:
The if-else is an extension of the simple if statement. The if –else statement evaluates the condition, whether the condition is true then the If block will be executed otherwise the else block will be executed, not both. The general form is
if test condition:
If block
else:
else block
statement-x
num = float(input("Enter a number: "))
if num > 0:
print("Positive Number ")
else:
print("Negative Number ")
Output:
Enter a number 5
Positive Number
Control statements are used to change the order of
sequence of execution based on some conditions. Various control statements in python are if statement,
for statement, while statement, break, continue and pass.
Decision making
and Branching / Conditional / if statements
If statement is a powerful
decision-making statement and used to control the flow of execution of
statements. Basically it is a two way decision statement and is used with a
keyword if and test condition. It allows computer to evaluate the condition
first and then, depending on the condition transfers the control to a
particular statement. Python supports the following statements in order to
achieve decision making capabilities
1.
If statement
2.
If –else
3.
Nested If
4. elif
A statement is an instruction that
a Python interpreter can execute. In python we use various statements to write
the code. Some of the statements available in Python are assignment
statement, print statement, control flow and the import statement.
Assignment
Statement:
Assignment statements are used to
set value to a variable
Ex: a = 10
in this statement value 10 is stored into variable a.
we can use assignment statement in evaluating an expression
f = c *9.0/5.0 + 32
This expression converts Celsius into Fahrenheit
We can assign several variables at once
a = b = c =10
Python permits number of variables to assign with different values with
comma separated values
x , y = 10,20
is same as
x = 10
y =
20
Input and
Output Statements
Input from the
user: We use input function to read data from user,
>>>input(“Enter
a number”)
…Enter a number 10
'10' Here, we can see that the entered value 10 is
a string, not a number. To convert this into a number we can use int() or
float() functions.
>>>
int(10)
10
>>>float(10)
10.0
Output:
print
statement: In python we
use print statement to display output in
console
>>>
print(“Hello world”)
will display Hello world as output
formatting
output
The print
statement produces a more readable output, by omitting the enclosing quotes and
by printing escape sequences, comma separator and special characters:
\'
display ' \" display "\t tab space \n new line
An operator is a symbol that tells the computer to perform certain mathematical or logical manipulations. Operators are used in programs to manipulate data and variables.
Ex:
c = a + b
In
this statement +, = are operators
and a, b, c are operands (variables).in this instruction the sum of two
variables a, b is carried out and the result is stored in variable c.
Operators
in Python
1. Arithmetic Operators
2. Relational Operators
(Comparison Operators)
3. Logical Operators
4. Bitwise operators
5. Assignment Operators
Arithmetic Operators: All the
arithmetic operators will perform basic calculations. The operators +,-,*, /,
//, % all work the same way as in other languages.
Python
Program Demonstrating the use of arithmetic operators
|
a = int (input
("Enter First Value")) b = int (input
("Enter Second Value")) print("sum", a+b) print("difference", a-b) print("product", a*b) print("division", a/b) print("modulus", a%b) print("floor division", a//b) print("exponent", a**2)
|
Arith.py
Relational Operators: Relational
Operators used in comparing the quantities and to formulate some conditions.
The value of a relational expression is either true or false.
Ex: 10 < 100 is true
100 < 10 is false
|
Operator |
Meaning |
|
< <= > >= == != |
Is less than Is less than or equal to Is greater than Is greater than or equal to Is equal to Is not equal to |
Table: Relational
Operators
|
a = int (input
("Enter First Value")) b = int (input
("Enter Second Value")) print("less than: ",a<b) print("less than
or equal to: ",a<=b) print("greater
than: ",a>b) print("greater than
or equal to: ",a>=b) print("equal
to:" ,a==b)
|
Logical Operators: In order to evaluate more than one condition we use
logical operators.in python we use and,
or, not as logical operators
|
Operator |
Meaning |
|
and or
not
|
logical And
logical Or
logical Not |
Python Program Demonstrating the use of Logical operators
|
a = True b = False print(a and b) print(a or b) print(not a) |
Output:
Bitwise operators: we use bitwise operators to manipulate data at bit
level.
|
Operator |
Meaning |
|
& | ^ << >> ~ |
Bitwise AND Bitwise Or Bitwise Exclusive Or Shift left Shift Right Bitwise Inverse |
Table: Bitwise operators
Python Program Demonstrating the use of Bitwise operators
|
a = int(input
("Enter First Value")) b = int(input
("Enter Second Value")) print("Bitwise AND
:",a&b) print("Bitwise Or
:",a|b) print("Bitwise
Exclusive Or :",a^b) print("Bitwise
Inverse :",~a) print("Shift left
:",a<<b) print("Shift Right
:",a>>b) |
ASSIGNMENT Operators: Assignment operator used to store some value (right side)into variable(left side). Compound-assignment operators provide a shorter syntax for assigning the result of an arithmetic or bitwise operator. They perform the operation on the two operands before assigning the result to the first operand.
|
Simple assignment
statement |
Short Hand Operator |
|
a
= a+1 a
= a-1 a
= a* 1 a
= a / 1 a
= a % b a = a&b a = a | b a = a ^ b a = a << b a = a >> b
|
a
+= 1 a
-=1 a
*=1 a
/=1 a
%= b a &= b a |= b a ^=
b a <<= b a >>= b |
Table: Assignment Operators
Python Program Demonstrating the use of Assignment operators
|
a = int(input
("Enter First Value")) b = int(input
("Enter First Value")) a += b print("+=",a) a -= b print("-=",a) a *= b print("*=",a) a /= b print("/=",a) a %= b print("%=",a) a //=b print("//=",a) a **=b print("**=",a) a &= b print("&=",a) a |= b print("|=",a) a ^= b print("^=",a) a <<= b print("<<=",a) a >>= b print(">>=",a)
|
Output:
Special Operators:
Membership Operators: in and not in are membership operators in Python.
Operator
Meaning
in
not in
Member of sequence
Not a member of sequence
Table:Membership Operators
Python
Program Demonstrating the use of membership operators
|
list1 = [1,2,3,'Ram','Rani',3.2] print(1 in list1) print(1 not in list1) print('Ram' in list1) print(5.5 not in list1) |
Output:
Operator
Meaning
is
is not
Same memory location
Not same memory location
Table: Identity Operators
Python Program Demonstrating the use of Identity operators
|
#for integer values a = int(input
("Enter First Value")) b = int(input
("Enter Second Value")) print("IS",a
is b) print("iS NOT
:",a is not b) #for string values s1 = 'Hello' s2 = 'Hello' print(s1 is s2) #for list L1 = [1,2,3] L2 = [1,2,3] Print(L1 is L2) |
Output:
