Variables : Types of variables in Python

Variables in Python

Syntax:

            variable_name = value

• There is no datatype declaration concept in python, datatype of variable will be decided at run time

• Datatype is dynamic type

Important

• type(variable_name)            will provide datatype of variable

• id(variable_name)                will provide address variable_name is referring.

Lets have a look at below example, this will prove 2 points discussed in "important points to remember section"

• Datatype is a run time allocation.

• Everything in Python is Object

>>> a = 10
>>> b = 10.25
>>> c = 'AETies'
 
>>> print(type(a))
>>> <class 'int'>
>>> print(type(b))
>>> <class 'float'>
>>> print(type(c))
>>> <class 'str'>
 

The above example have a, b and c variables.

We have not defined any variable with datatype,  datatype is decided dynamically at run time.

so we can see that

• a belongs to int class, so a is int class object

• b belongs to float class, so b is float class object

• c belongs to str class, so c is as str class object  (str is string)

Types of Variables in Python

We have 5 types of variables in Python. Among 5 types, 2 totally belongs to Class.

Example:

#program

def add(a, b) :             
    print("a: ", a, "\nb: ", b, "\nd :", d)
    c = a + b
    global e                # declaring global variable inside function
    e = "global Variable defined inside a function with keyword global"
    return c
d = 10.25
result = add (5, 10)
print(e)                    # trying to print global variable defined inside function
print("sum :",result)
print(c)                    # trying to print local variable outside function

#output

a:  5
b:  10
d : 10.25
global Variable defined inside a function with keyword global
sum : 15
Traceback (most recent call last):
  File "C:/Self_Practice_Er_M_S_Dandyan/Python/Pycharm/xml/main.py", line 11, in <module>
    print(c)                    # trying to print local variable outside function
NameError: name 'c' is not defined

Process finished with exit code 1

LOCAL Variable

• Variables defined inside a function.

• Scope is in the defined function only.

• Memory will be allocated at function calling time.

• As per above example,
• 'c' is a local variable as it is defined inside the function.

• when we tried to call outside function, it thrown error.

GLOBAL Variable

• Variables defined inside a module , but outside the functions.

• Scope is inside the defined module and other modules.

• Memory will be allocated, when application execution starts.

• We can define a global variable inside a function with the help of keyword "global".

• As per example,
• 'd' is a global variable defined outside a function.

• 'e' is a global variable declared inside function with keyword 'global'.

PARAMETERIZED Variable

• Variables defined in Function/Method definition inside parameters.

• Scope is through out the function.

• As per example
• 'a' and 'b' are parameterized variables

STATIC Variable

• Variables defined inside a Class but outside the method.

• Memory is allocated at Class loading time.

• Without creating Object to Class, we can access Static variables with Class name

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INSTANCE Variable

• Variable defined inside Method with keyword self

• Memory is created at Class Object creation time

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