Python Variables

Variable is a name that is used to refer to memory location. Python variable is also known as an identifier and used to hold value.

In Python, we don't need to specify the type of variable because Python is a infer language and smart enough to get variable type.

Variable names can be a group of both the letters and digits, but they have to begin with a letter or an underscore.

Identifier Naming

Variables are the example of identifiers. An Identifier is used to identify the literals used in the program. The rules to name an identifier are given below.

• The first character of the variable must be an alphabet or underscore ( _ ).
• All the characters except the first character may be an alphabet of lower-case(a-z), upper-case (A-Z), underscore, or digit (0-9).
• Identifier name must not contain any white-space, or special character (!, @, #, %, ^, &, *).
• Identifier name must not be similar to any keyword defined in the language.
• Identifier names are case sensitive; for example, my name, and MyName is not the same.
• Examples of valid identifiers: a123, _n, n_9, etc.
• Examples of invalid identifiers: 1a, n%4, n 9, etc.

Declaring Variable and Assigning Values

Python does not bind us to declare a variable before using it in the application. It allows us to create a variable at the required time.

We don't need to declare explicitly variable in Python. When we assign any value to the variable, that variable is declared automatically.

The equal (=) operator is used to assign value to a variable.

Object References

It is necessary to understand how the Python interpreter works when we declare a variable. The process of treating variables is somewhat different from many other programming languages.

Python is the highly object-oriented programming language; that's why every data item belongs to a specific type of class. Consider the following example.

1. print("Python")  

Python Variable Types

There are two types of variables in Python - Local variable and Global variable. Let's understand the following variables.

Local Variable

Local variables are the variables that declared inside the function and have scope within the function. Let's understand the following example.

Example -

1. # Declaring a function  
2. def add():  
3.     # Defining local variables. They has scope only within a function  
4.     a = 20  
5.     b = 30  
6.     c = a + b  
7.     print("The sum is:", c)  
8.   
9. # Calling a function  
10. add()  

Global Variables

Global variables can be used throughout the program, and its scope is in the entire program. We can use global variables inside or outside the function.

Example -

1. # Declare a variable and initialize it  
2. x = 101  
3.   
4. # Global variable in function  
5. def mainFunction():  
6.     # printing a global variable  
7.     global x  
8.     print(x)  
9.     # modifying a global variable  
10.     x = 'Welcome To Javatpoint'  
11.     print(x)  
12.   
13. mainFunction()  
14. print(x)