variable.txt

                        variableit 
it is a container in which we store value.
In python we can define variable by using 
variable name=value
we do not need to define data type of variable it automatically detect variable type
>>> x=291.291
>>> y=291
>>> x+y
582.2909999999999
>>> _+291
873.2909999999999
_ underscore is used for output for previous operation

string is a array of characters
>>> name[0]
'm'
>>> name[-3]
'n'
we can also use negative number it will give from last charcter
>>> name[-1]
'h'
>>> name[-5]

it will print the character start with 0 and end with index 2
>>> name[0:3]
'man'
name[1:] it will start with 1 and it will go till the end 
name[:3] it will start with 0 and end with index 2
string in python is immutable that mean once we assign the charcater it cannot change it 
name[0]='d' it is not possible
len function return number of character in string 
len(name)
it will return length string variable name