Variable in python?

 Variable in Python

• It is a name of storage space which is used to store data.
• It's value may be changed.
• It always contains last value stored to it.
• There is no need to declare a variable in python.
• Variable is created by assigning a value to it.

Variable Initialization

name="Tom"
rollno=205
marks=85.6

• Here name rollno and marks are the name of variables.
• Value of name is Tom,rollno is 205 and marks is 85.6

Printing value of variable

• We can print the value of a variable using print() function.

#creating variables
name="Tom"
rollno=205
marks=85.6
#printing value of varibales
print("Name:",name)
print("Roll:",rollno)
print("Marks:",marks)
"""
***Output***
Name: Tom
Roll: 205
Marks: 85.6
"""

Assigning single value to multiple variable

• We can assign a single value to multiple variables using single statement in python.

#creating variables
a=b=c=90
#printing value of varibales
print("a:",a)
print("b:",b)
print("c:",c)
"""
***Output***
a: 90
b: 90
c: 90
"""

Assigning multiple values to multiple variables

• We can also assign multiple values to multiple variables using single statement in python.

#creating variables
a,b,c=70,80,90
#printing value of varibales
print("a:",a)
print("b:",b)
print("c:",c)
"""
***Output***
a: 70
b: 80
c: 90
"""

Rules to define a variable

• The first letter of a variable should be alphabet or underscore(_).
• The first letter of variable should not be digit.
• After first character it may be combination of alphabets and digits.
• Blank spaces are not allowed in variable name.
• Variable name should not be a keyword.
• Variable names are case sensitive for example marks and MARKS are different variables.

Local Variable

• A variable declared inside the body of the function is called local variable.
• Local variable can be used only inside that function in which it is defined.

#function definition
def add():
    #creating variable
    x=50
    y=30
    z=x+y
    print("Add=",z)
#Calling funtion
add()
#This line will raise an error
#because x is local variable
#and it can't be accessed
#outside function
print(x)
"""
***Output***
Add= 80
NameError: name 'x' is not defined
"""

Global Variable

• A variable which is created outside a function is called global variable.
• It can be used anywhere in the program.

#creating global variable
x=50
y=30
def add():
    #accessing global variable
    #inside a function
    print("Inside function Sum=",x+y)
#Calling funtion
add()
#accessing global variable
#outside a function
print("Outside function Sum=",x+y)
"""
***Output***
Inside function Sum= 80
Outside function Sum= 80
"""
 

Local and Global variable with same name

#creating global variable
x=50
def add():
    x=20
    # this line will print 20
    print("Inside function x=",x)
#Calling funtion
add()
#this line will print 50
print("Outside function x=",x)
"""
***Output***
Inside function x= 20
Outside function x= 50
"""
 

global keyword

• Simply we can't modify the value of global variable inside a function but by using global keyword we can modify the value of global variable inside a function.

#creating global variable
x=50
def add():
    global  x
    #updating value of x
    x=20
    # this line will print 20
    print("Inside function x=",x)
#Calling funtion
add()
#this line will print 20
print("Outside function x=",x)
"""
***Output***
Inside function x= 20
Outside function x= 20
"""