Variable and Data Type

Data Type

There are several data types for Python:

To get a data type in Python, we use the type() function. Example:

          

          
    x=6
    print(type(x)) #the output will be int
          
        


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Variable Name

The general rules for naming variables are:

• Names can contain letters, digits, and underscores
• Names must begin with a letter or an underscore (_)
• Names are case-sensitive (lowercase and uppercase letters have different meanings)
• Names cannot contain whitespaces or special characters ($, #, %, etc.)
• Names cannot contain reserved words, such as int, float, etc.

Creating Variable

Creating variables also known as declaring variables is an action of making a variable to store data.

Example: x = 5

Assign Value to Variable

Assigning value means storing a value in a variable. You can assign a value when declaring a variable.

Syntax: variable_name = value;

Example:

            

            
    x = 5
    y = 'me'
            
          


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To change a variable value, we just need to assign a new value to an existing variable. The new assigned value will overwrite the previous value.

Example:

            

            
    x = 20 	#the value of x is 20
    x = 100 	#the value of x is now 100
            
          


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We can also copy the value of a variable to another variable.

Syntax: variable_name1 = variable_name2;

Example:

            

            
    x = 10
    y = x	#the value of y becomes 10
            
          


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In Python, the data type is set automatically when we assign a value to a variable.

Casting

Casting, also known as type conversion is an action of converting a value of one data type to another data type. For example, the conversion of int to float or vice versa. There are two types of conversion in Python:

1. Implicit Conversion

This conversion occurs automatically when we assign a value to a variable.

Example:

              

              
    x = 8 	#x is automatically set to int
              
            
        

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2. Explicit Conversion

This conversion is done manually by using constructor functions. There are three well-known constructor functions:

• int() - constructs an integer number
• float() - constructs a float number
• str() - constructs a string



Example:

                

                
    x = int(9.12)	#x will be 9
    y = float(8)	#y will be 8.0
    z = str(100)	#z will be '100'
                
              
  

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Variable Scope

Scope is the area in which a variable can be used or can be accessed. For Python variables, there are 2 types of scopes, local and global. Local variable exists and can only be accessed in a particular function, while global variable can be accessed by all functions in the entire program.

Example:

            

            
    x = "Hello!" 	#this is a global variable

    def myFunc(){
        y = "Hi!"	#this is a local variable
    } 
            
          


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We can also use the global keyword to make a local variable become global variable.

          

          
    def myFunc(){
        global y
        y = "Hi!"	#y is now a global variable
    } 
          
        


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