Python - Things to know before proceed - Variable Tutorial

Python variable is a container in memory (storage area) to hold value or data. In python, there is no need to assign a variable with datatype because python can detect the data type of a variable automatically.

We can assign a value to a variable by simply using the assignment operator (=).

For example-

a=10

print(a)

b= 'fresherbell.com'

print(b)

Run Program

Here we have created a variable named a and b with no datatype and assigned the value integer 10 to variable a and string “fresherbell.com” to variable b.

Rules and Naming Convention for Variables

• Variable can contain a combination of letters in lowercase (a to z) or uppercase (A to Z) or digits (0 to 9) or an underscore (_). For example-

a_A1=10

print(a_A1)

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• Variable name must not contain any white-space, or special character (!, @, #, %, ^, &, *).
• The variable name must not be similar to any keyword defined in the language.
• The variable name is case sensitive, i.e a and A has a different meaning.

Assigning a single value to multiple variable

a=b=c=10

print(a)

print(b)

print(c)

Run Program

Assigning multiple values to multiple variable

a,b,c=10,20,30

print(a)

print(b)

print(c)

Run Program

Type of Variable in Python

• Local Variable

A local variable is a variable that is declared inside the function and has scope inside the function.

def localvariable():
    
    a=10
    
    print (a)
    
localvariable()
#It will give error - name 'a' is not defined
print(a) 

Run Program

In the above example, we declare a local variable inside function localvariable(), which will print a value of 10 on calling a function localvariable().

Also, we tried to print variable outside function localvariable(), which will give an error that variable a is not defined.

Hence local variables will only work within its scope.

• Global Variable

A global variable can be used anywhere in the program. Its scope is within the entire program.

The variable outside function is by default global. To declare a global variable inside a function use the global keyword behind the variable.

a=20 # Global Variable
def localvariable():
    global b
    b=10
    print (b)
localvariable()
print(a)
print(b)

Run Program

Constants

A constant is a type of variable, whose value cannot be changed. Constant is always written in CAPS or UpperCase.

ABC = 10
PI = 3.14