Variables and Data types in Python

Variables in Python

A variable is a container used to store data values. In Python, you don’t need to declare the type of a variable, it is automatically assigned.

Example:

name = "Aman"
age = 20
height = 5.8

print(name)
print(age)
print(height)

Rules for naming variables:

• Must start with a letter or underscore ( _ )
• Cannot start with a number
• Cannot use keywords (like if, for, while) # will learn about keywords in upcoming topics
• Case-sensitive (Name and name are different)

x = 5
5x = 7  # wrong
x5 = 8  
_g = 9       

Data Types in Python

we will mainly study numbers, strings and list in these “Introduction to Python Programming” Syllabus/notes. Your can learn more about python in detail from our advance courses available on site. or you can search it via search bar on our website.

A data type defines the kind of value a variable can hold. We just need to type the require data with the variables.

1. Numbers

Python supports different types of numbers:

• Integer (int) → whole numbers
• Float (float) → decimal numbers

Example:

a = 10        # Integer
b = 3.14      # Float

print(a)       
print(b)

Output :

10
3.14

2. Strings

A string is a sequence of characters enclosed in single of double quotes.

Example:

name = "Python"
message = 'Hello World'

print(name)
print(message)

Python
Hello World

3. List

A list in Python is a collection used to store multiple values in a single variable. It can store multiple types of data in it.

x = [3,5,6,7,8]
y = [4,5.7,"Hello",8]

print(x)
print(y)

[3, 5, 6, 7, 8]
[4, 5.7, 'Hello', 8]

Checking Data Types

You can check the type of any variable using type() function:

x = 10
y = "Hello"
z = [4, 5.7, 'Hello', 8]

print(type(x))
print(type(y))
print(type(z))

<class 'int'>
<class 'str'>
<class 'list'>

Type Conversion (Type Casting)

Type conversion means changing one data type into another.

1. Convert to Integer

x = "10"                 # it is string because it is in quotes
y = int(x)               # we are using variable x in int( ) function

print(y)
print(type(y))

10
<class 'int'>

2. Convert to Float

x = 5 
y = float(x)

print(y)
print(type(y))

5.0
<class 'float'>

3. Convert to String

x = 100
y = str(x)

print(y)
print(type(y))

100
<class 'str'>

Not all conversions are valid:

x = "hello"        # converting letters string to integer
y = int(x)          # This will cause an error

But we can do this

x = "100"
y = int(x)

print(y)
print(type(y))