Python Variables

What is a Variable?

Variables are the reserved memory locations to store values(data). This means that when you create a variable you reserve some space in memory.

Location of Variable

id is used to find the address or location of the variables.

# id is used to find the address of the variables 
age = 20
print(id(age))

name ="Python"
print(id(name))

company = "" 
print(id(company))

Output:
140736363164000
1534947487848
1534917180528
    

Rules for Python Variables

  • An variable is a sequence of letters such as uppercase(A to Z),lowercase(a to z),digits(0 to 9) and an underscore (_) ie “Alphanumeric “ characters.
  • It does not allow punctuation characters such as @, $, and % within variable.
  • It is a case sensitive ( Eg: Students and student are different variable)
  • Reserved words cannot be used as variable.
  • It cannot start with a digit. (Python thinks it is a number)
    Eg: 1student is invalid 
         student1 is valid 
    	      
  • Creating and Assigning Values to Variables

    A variable is created the moment you first assign a value to it. The equal sign (=) is used to assign values to variables.

    # Declaring the variables 
    rollnumber  = 12345 # rollnumber  is integer
    name = "Santosh" # name is string
    marks = 80.5  # marks is float
    print(rollnumber,name,marks)
    
    Output:
    12345 Santosh 80.5
        

    Conclusion: Python variables do not need explicit declaration to reserve memory space. The declaration happens automatically when you assign a value to a variable. Based on the data type of a variable, the interpreter allocates memory and decides what can be stored in the reserved memory. Note: An interpreter is a program that reads and executes code

    Multiple Assignment

    # 1. Multiple variables in single row
    a,b,c,d = 10,20,30,40
    print(a,b,c,d)
    
    Output:
    10 20 30 40
    
    # 2. Multiple variables of different data types
    name,rollnumber,marks="Santosh",12345,85.75
    print(name,rollnumber,marks)
    
    Output:
    Santosh 12345 85.75
    
    # 3. Single value to several variables
    graph1 = graph2 = graph3 = "DataScience"
    print(graph1,graph2,graph3)
    
    Output:
    DataScience DataScience DataScience
    

    Memory Allocation

    If the value is same, the memory location will be also same.

    # id is used to find the address of the varaible
    print(id(graph1))
    print(id(graph2))
    
    Output:
    1534987626544
    1534987626544
    
    # Updating the value of varible (graph2) and checking the memory location
    graph2= "Python"
    print(id(graph2))
    
    Output:
    1534947487848
    

    Conclusion: The performance of our coding depends on 2 things.
    1. Code logic
    2. Memory allocation(how we handle variables)

    Total Website Visits: 40425
    © Copyright 2018 - 2020. All Rights Reserved.

    Developed by Vinoth Rathinam

    Leave a Reply