This blog explores Python variable usage and functionalities.

phone = 1234567890
pi    = 3.14
name  = "python programming"
using_python   = True
example_none   = None
simple_list    = [1,2,3]
simple_dict    = {"name":"python"}
simple_set     = {1,1,1,1,1.0}
simple_tuple   = (1,2,3)
complex_number = 3+5j

print("number     = ",phone)
print("float      = ",pi)
print("boolean    = ",using_python)
print("None       = ",example_none)
print("list       = ",simple_list)
print("dictionary = ",simple_dict)
print("set        = ",simple_set)
print("tuple      = ",simple_tuple)
print("complex    = ",complex_number)

number     =  1234567890
float      =  3.14
boolean    =  True
None       =  None
list       =  [1, 2, 3]
dictionary =  {'name': 'python'}
set        =  {1}
tuple      =  (1, 2, 3)
complex    =  (3+5j)

print(type(phone))
print(type(pi))
print(type(using_python))
print(type(simple_list))
print(type(simple_dict))
print(type(simple_set))
print(type(simple_tuple))
print(type(complex_number))
print(type(example_none))

<class 'int'>
<class 'float'>
<class 'bool'>
<class 'list'>
<class 'dict'>
<class 'set'>
<class 'tuple'>
<class 'complex'>
<class 'NoneType'>

b1 = bytes([1,2,3,4])
bo = memoryview(b1)
print("byte example :",bo[0])

byte example : 1

b2 = bytearray(b"aaaa")
bo = memoryview(b2)
print("byte array :",b2)
bo[1] = 98
bo[2] = 99
bo[3] = 100
print("byte array :",b2)

byte array : bytearray(b'aaaa')
byte array : bytearray(b'abcd')

Other Data Types

Frozenset

A frozenset is similar to a normal set, but it is immutable.

test_frozenset = frozenset([1,2,1])
for i in test_frozenset:
    print("frozen set item :",i)

Output

frozen set item : 1
frozen set item : 2

Range

The range data type specifies a number range (e.g., 1-10).

It is mostly used in loops and mathematical operations.

a = range(3)
print("a = ",a)
print("type = ",type(a))

Output

a =  range(0, 3)
type =  <class 'range'>

Type Casting

Type casting is converting a data type into another. Try explicit type casting to change data types.

value = 1
numbers = [1,2,3]
print("type casting int     : ",type(int(value)))
print("type casting float   : ",type(float(value)))
print("type casting string  : ",type(str(value)))
print("type casting boolean : ",type(bool("True")))
print("type casting list    : ",type(list(numbers)))
print("type casting set     : ",type(set(numbers)))
print("type casting tuple   : ",type(tuple(numbers)))

Output

type casting int     :  <class 'int'>
type casting float   :  <class 'float'>
type casting string  :  <class 'str'>
type casting boolean :  <class 'bool'>
type casting list    :  <class 'list'>
type casting set     :  <class 'set'>
type casting tuple   :  <class 'tuple'>

Delete Variable

Delete an existing variable using Python’s del keyword.

temp = 1
print("temp variable is : ",temp)
del temp
# print(temp)  => throw NameError : temp not defined

Output

temp variable is :  1

Find Variable Memory Address

Use the id() function to find the memory address of a variable.

temp = "hi"
print("address of temp variable : ",id(temp))

Output

address of temp variable :  140710894284672

Constants

Python does not have a direct keyword for constants, but namedtuple can be used to create constants.

from collections import namedtuple
const = namedtuple("const",["PI"])
math = const(3.14)

print("namedtuple PI = ",math.PI)
print("namedtuple type =",type(math))

Output

namedtuple PI =  3.14
namedtuple type = <class '__main__.const'>

Global Keyword

Before understanding global keyword, understand function-scoped variables.

• Function inside variable are stored in stack memory.
• A function cannot modify an outside (global) variable directly, but it can access it.
• To create a reference to a global variable inside a function, use the global keyword.

message = "Hi"
def dummy():
    global message 
    message = message+" all"

dummy()
print(message)

Output

Hi all

Explicit Type Hint

Type hints are mostly used in function parameters and arguments.

They improve code readability and help developers understand variable types.

-> float : It indicates the return data type.

def area_of_circle(radius :float) -> float:
    PI :float = 3.14
    return PI * (radius * radius)

print("calculate area of circle = ",area_of_circle(2))

Output

calculate area of circle =  12.56

hi,everyody
I am kavin. I am going to write which I learnt I my class.

Variables

A variable in Python is a symbolic name that references or points to an object. Once a variable is assigned a value, it can be used to refer to that value throughout the program. Variables act as containers for storing data values.

How to name a variables

1.Start with a letter or an underscore.
2.Followed by letters, digits, or underscores.
3.Case-sensitive
4.Don't use Python Keywords

Examples of Valid Variable Names:
my_variable
variable1
_hidden_variable
userName


Assigning Values to Variables

In Python, the assignment operator = is used to assign values to variables. The syntax is straightforward: variable_name = value.
eg:

>>>name="kavin"
>>>print(name)

>>>kavin

Multiple Assignments

Python allows you to assign values to multiple variables in a single line. This can make your code more concise and readable.
eg:

>>>a,b,c=1,2,3
>>>print(a,b,c)

Variable Types

Python is a dynamically typed language, which means you don’t need to declare the type of a variable when assigning a value to it. The type is inferred at runtime based on the assigned value.
eg:

>>>my_variable="10"

>>>my_variable is an integer

You can check the type of a variable using the type() function.
eg:

>>>type("hello")

>>><class'str'>

Constants

In Python, constants are variables whose values are not meant to change. By convention, constants are typically written in all uppercase letters with underscores separating words.
eg:

>>>PI=22/7

Data Types

Data types are the different kinds of values that you can store and work with.

1.Numeric Types
*Integer (int): Whole numbers.

>>>value=23

*Float (float): Decimal numbers.

>>>value=23.5

*Complex (complex): Complex numbers.

>>>value=2+3j

2. Text Type

String (str): Sequence of characters.
eg:

>>>message="hello mac"

3. Boolean Type

Boolean (bool): Represents True or False.
eg:

>>>my_project=True

4. None Type

NoneType: Represents the absence of a value
eg:

>>>result=none

5. Sequence Types

*List (list): Ordered, mutable collection
eg:

>>>fruits=[apple,cherry,mango]

*Tuple (tuple): Ordered, immutable collection.
eg:

>>>coordinates(3,4)

*Range (range): Sequence of numbers.
eg:

>>>number=range(1,10)

6. Mapping Type

Dictionary (dict): Unordered, mutable collection of key-value pairs.
eg:

>>>person={"name":"kavin","url":"https://www.kavin.com"}

7.Set Type

Set (set): Unordered collection of unique elements.
Eg:

>>>unique_number={2,3,4}

Frozenset (frozenset): Immutable set.
eg:

>>>frozen_set=frozena([2,3,4])

Checking Data Type

Syntax: type(variable_name)
eg:

>>>name="kavin"
>>>print(type(name))

>>> <class'int'>

this is the things which i learnt in the class of Variables, Constants and Data Types.
Thank You