Variable and Datatypes

What is a Variable

In programming, a variable is a named container that is used to store data. It is a way to refer to a memory location that holds a value. Variables are fundamental in programming as they allow us to store and manipulate data during the execution of a program.

Declaring Variables in Python

In Python, you can declare a variable by assigning a value to it using the assignment operator =. Here's the general syntax for declaring a variable:

variable_name = value

Example :

name = "Ankita"

In the above example, we declared a variable named name and assigned the value Ankita to it.

Rules to declare a variable in python

1. A variable name must start with a letter a-z or A-Z or the underscore _ character.
2. A variable name cannot start with a number.
3. Variable names are case-sensitive, which means name and Name are considered different variables.
4. A variable name can not used reserved keyword
5. A variable name can include a-z,A-z, 0-9, and _ Here are some examples of valid and invalid variable names:

Valid variable names

age = 21
student_name = "John"
_total = 100
my_variable_2 = True

Invalid variable names

2name = "Alice"  # Cannot start with a number
first-name = "Bob"  # Cannot use hyphens
class = "Math"  # Cannot use reserved keywords

Let's learn by examples

variable.py

age=21
print(age)

Output

21

In the above example, In the First line we can create one variable and the name of that variable is age. In this variable, we store the 21 value And In 2 lines we can print the value of that variable..

datatype.py

name="sakshi"
age=21
weight=45.65

print("Name: ",name)
print("Age: ",age)
print("Weight: ",weight)

Output

Name: sakshi
Age: 21
Weight: 45.65

In the above example, In the First line we create 1st variable and the name of that variable is the name. In this variable, we store the Sakshi value, In the second line we create 2nd variable, and the name of that variable is age. In this variable, we store the 21 value In the third line we create the 3rd variable and the name of that variable is weight. In this variable, we store the 45.65. In the fifth line, we print the value of the name variable but in a formatted way, In the sixth line, we print the value of the age variable but in a formatted way In the seventh line, we print the value of the weight variable but in a formatted way .

multiple-assignment.py

a,b,c=10,20,30
print(a)
print(b)
print(c)

Output

10
20
30

In Python, One of the beautiful things that is we can create multiple declarations and we can assign multiple values. So, in the above example, we can create three variables a, b, and c means multiple declarations and we assign multiple values 10, 20, and 30 means multiple assignments. In the 2nd line, we print the value of variable a, the 3rd line print value of variable b, 4th line print the value of variable c.

reassignment.py

val=10
print(val)
val=20
print(val)
val=30
val=40
val=50
print(val)

Output

10
20
50

A variable can only store one value at a time so that's why In the above example the output is 10, 20 and 50.

type() function in python

The type() function is used to check the type of datatype.

type(variablename)

Example :

name = "Ankita"
age = 25
weight = 50.50
print(type(name))
print(type(age))
print(type(weight))

Output :

 <class 'str'><br/>
 <class 'int'><br/>
 <class 'float'><br/>

Example explanation :

In the above example, In the First line we create 1st variable and the name of that variable is the name. In this variable, we store the Ankita value, In the second line we create 2nd variable, and the name of that variable is age. In this variable, we store the 25 value. In the third line, we create 3rd variable and the name of that variable is weight. In this variable, we store the 50.50. In the fifth line, we print the value of the name variable but we have to check the type of the name variable so we used to print(type(name)).In the sixth line, we have to check the type of age variable so we used print(type(age)).In the seventh line, we have to check the type of weight variable so e used print(type(weight)).

Another Example :

name = "Harshda"
age = 22
weight = 41.70
print(type(name))
print(type(age))
print(type(weight))

Output :

 <class 'str'><br/>
 <class 'int'><br/>
 <class 'float'><br/>