Python Variables & Data Types Tutorial for Beginners

Python Variables and Data Types

Variables and data types are fundamental concepts in Python programming. Almost every Python program uses variables to store, process, and manipulate information.

In this lesson, you will learn how Python variables work, how dynamic typing works, Python's built-in numeric and text types, type checking, type conversion, user input, output formatting, multiple assignment, and variable swapping.

By the end of this lesson, you will be able to create variables, identify Python data types, convert values between types, accept input from users, and format program output effectively.

What Is a Variable in Python?

A variable is a name that refers to an object containing a value.

A simple way to visualize a variable is:

text
1Variable Name ─────► Object / Value
2     age      ─────► 20

In Python, you create a variable by assigning a value to a name using the = operator.

Syntax

python
1variable_name = value

Basic Example

python
1name = "Ankit"
2age = 22
3city = "Delhi"
4
5print(name)
6print(age)
7print(city)

Output:

text
1Ankit
222
3Delhi

Python does not require you to specify the variable's type when assigning a value.

python
1name = "Ankit"
2age = 22

Python determines the type of each value at runtime.

Understanding Variable Assignment

It is useful to understand that Python variables are names bound to objects, rather than traditional boxes that directly contain values.

For example:

python
1age = 22

Conceptually:

text
1age ─────► 22

The name age refers to an integer object whose value is 22.

If you later write:

python
1age = 30

the name age is now bound to another integer object:

text
1age ─────► 30

This model becomes particularly important when working with mutable objects such as lists and dictionaries.

Variable Naming Rules

Python has specific rules for naming variables.

Valid Variable Names

python
1name = "Ankit"
2_age = 22
3student_name = "Rahul"
4student2 = "Aman"
5total_marks = 450

Invalid Variable Names

python
12name = "Ankit"       # Cannot start with a number
2my-name = "Python"    # Hyphen is not allowed
3class = "Python"     # Reserved keyword

A Python identifier can contain:

Letters (a-z, A-Z)
Numbers (0-9)
Underscores (_)

However, it cannot begin with a number.

Python identifiers are also case-sensitive.

python
1name = "Alice"
2Name = "Bob"
3
4print(name)
5print(Name)

Output:

text
1Alice
2Bob

name and Name are different identifiers.

Python Variable Naming Best Practices

Use descriptive names that communicate what the value represents.

Good:

python
1student_name = "Ankit"
2total_marks = 450
3user_age = 22
4is_logged_in = True

Less descriptive:

python
1x = "Ankit"
2a = 450
3b = 22

For variables and functions, Python commonly follows the snake_case naming convention.

python
1first_name = "Alice"
2last_name = "Smith"
3total_price = 999.99

Good variable names make programs easier to read, debug, and maintain.

Dynamic Typing in Python

Python is a dynamically typed language.

This means you do not normally need to declare the type of a variable before assigning a value.

For example, in Java you might write:

java
1int age = 20;

In Python, you simply write:

python
1age = 20

Python determines that age refers to an integer object.

Changing the Type of a Variable

A Python name can later be rebound to an object of a different type.

python
1x = 10
2
3print(x)
4
5x = "Python"
6
7print(x)

Output:

text
110
2Python

The name x first refers to an integer and later refers to a string.

You can inspect the current type with type():

python
1data = 100
2print(type(data))
3
4data = 12.5
5print(type(data))
6
7data = True
8print(type(data))

Output:

text
1<class 'int'>
2<class 'float'>
3<class 'bool'>

Dynamic typing makes Python concise, but you still need to understand what type of object your code is working with.

Python Constants

Python does not provide a dedicated const keyword for creating immutable constants.

Instead, Python developers use a naming convention: constant names are normally written in uppercase.

python
1PI = 3.14159
2MAX_USERS = 100
3SITE_NAME = "Tech3Space"
4
5print(PI)
6print(MAX_USERS)
7print(SITE_NAME)

Output:

text
13.14159
2100
3Tech3Space

Uppercase names communicate that a value is intended to remain unchanged.

However, Python does not prevent reassignment:

python
1PI = 3.14
2
3PI = 5
4
5print(PI)

Output:

text
15

Therefore, uppercase names represent a convention rather than a language-enforced constant.

Python Variable References

Python variables are references to objects.

Consider:

python
1a = 10
2b = a
3
4print(a)
5print(b)

Output:

text
110
210

Both names currently refer to an integer object representing 10.

If you reassign a:

python
1a = 20
2
3print(a)
4print(b)

Output:

text
120
210

Reassigning a does not change what b refers to.

Mutable Objects and Shared References

The behavior becomes more important with mutable objects such as lists.

python
1list1 = [10, 20]
2list2 = list1
3
4list2.append(30)
5
6print(list1)
7print(list2)

Output:

text
1[10, 20, 30]
2[10, 20, 30]

Why did both lists change?

Because:

python
1list2 = list1

does not create a new list. Both names refer to the same list object.

Conceptually:

text
1list1 ──┐
2        ├──► [10, 20, 30]
3list2 ──┘

If you want an independent list, you can create a copy:

python
1list1 = [10, 20]
2list2 = list1.copy()
3
4list2.append(30)
5
6print(list1)
7print(list2)

Output:

text
1[10, 20]
2[10, 20, 30]

This distinction between assignment, references, and copying becomes increasingly important as you work with Python collections.

Using the id() Function

The built-in id() function returns an integer that identifies an object during its lifetime.

Example:

python
1a = 100
2b = a
3
4print(id(a))
5print(id(b))

In this example, both names refer to the same object, so they will normally have the same id() value.

Do not rely on id() as a permanent physical memory address. It is better understood as an identity value for the object within that Python process.

Python Numeric Data Types

Python provides three built-in numeric types:

int — integers
float — floating-point numbers
complex — complex numbers

Example:

python
1integer_number = 100
2decimal_number = 25.5
3complex_number = 3 + 4j
4
5print(integer_number)
6print(decimal_number)
7print(complex_number)

Output:

text
1100
225.5
3(3+4j)

Python Integer Type

An int represents whole numbers without a decimal point.

Examples:

text
110
2-5
31000
40

Example:

python
1marks = 95
2
3print(marks)
4print(type(marks))

Output:

text
195
2<class 'int'>

Python integers can represent arbitrarily large integers, limited primarily by available memory.

python
1large_number = 10 ** 100
2
3print(large_number)

Python handles this without requiring a separate "long integer" type.

Integer Arithmetic

Python supports common arithmetic operations.

python
1a = 15
2b = 4
3
4print(a + b)   # Addition
5print(a - b)   # Subtraction
6print(a * b)   # Multiplication
7print(a // b)  # Floor division
8print(a % b)   # Remainder
9print(a ** b)  # Exponentiation

Output:

The // operator performs floor division, while % returns the remainder.

For positive numbers:

python
1print(15 // 4)
2print(15 % 4)

Output:

text
13
23

Python Float Type

A float represents a floating-point number.

Examples:

text
13.14
212.75
30.5
4-8.25

Example:

python
1price = 99.99
2
3print(price)
4print(type(price))

Output:

text
199.99
2<class 'float'>

You can perform arithmetic operations with floating-point values.

python
1x = 5.5
2y = 2.5
3
4print(x + y)
5print(x * y)
6print(x / y)

Output:

text
18.0
213.75
32.2

Keep in mind that floating-point numbers can have small representation errors because many decimal fractions cannot be represented exactly in binary floating-point.

For applications such as financial calculations where exact decimal arithmetic is important, Python's decimal module may be more appropriate.

Python Complex Numbers

Python supports complex numbers using the j suffix for the imaginary component.

The general form is:

text
1a + bj

Example:

python
1z = 2 + 5j
2
3print(z)
4print(type(z))

Output:

text
1(2+5j)
2<class 'complex'>

You can access the real and imaginary components:

python
1z = 3 + 8j
2
3print(z.real)
4print(z.imag)

Output:

text
13.0
28.0

Complex numbers are useful in areas such as engineering, scientific computing, signal processing, and mathematics.

Python Boolean Type

The Boolean type, bool, has two values:

python
1True
2False

Example:

python
1is_student = True
2is_admin = False
3
4print(is_student)
5print(is_admin)

Output:

text
1True
2False

Booleans are frequently used in conditions.

python
1age = 20
2
3print(age >= 18)
4print(age < 18)

Output:

text
1True
2False

Comparison operators return Boolean values.

Python Strings

A string is a sequence of characters used to represent text.

Example:

python
1name = "Python"
2
3print(name)
4print(type(name))

Output:

text
1Python
2<class 'str'>

Python strings can be written using single or double quotes.

Single Quotes

python
1language = 'Python'

Double Quotes

python
1language = "Python"

Both create a string.

Multiline Strings

Triple-quoted strings can contain multiple lines.

python
1text = """Python
2is
3awesome"""
4
5print(text)

Output:

text
1Python
2is
3awesome

Triple-quoted strings are also commonly used for docstrings.

Accessing String Characters

Python strings are indexed starting from 0.

python
1word = "Python"
2
3print(word[0])
4print(word[2])
5print(word[-1])

Output:

text
1P
2t
3n

The indexes are:

text
1 P  y  t  h  o  n
2 0  1  2  3  4  5

Negative indexes start from the end:

text
1 P   y   t   h   o   n
2-6  -5  -4  -3  -2  -1

String Length

Use the built-in len() function to determine the number of characters in a string.

python
1name = "Programming"
2
3print(len(name))

Output:

text
111

Spaces are also counted as characters.

python
1text = "Hello World"
2
3print(len(text))

Output:

text
111

String Concatenation

You can combine strings using the + operator.

python
1first = "Hello"
2second = "World"
3
4message = first + " " + second
5
6print(message)

Output:

text
1Hello World

String Repetition

The * operator can repeat a string.

python
1print("Python " * 3)

Output:

text
1Python Python Python

Python None

None is a special Python object that represents the absence of a value.

Example:

python
1data = None
2
3print(data)
4print(type(data))

Output:

text
1None
2<class 'NoneType'>

None is commonly used when a value is currently unavailable or when a function intentionally returns no meaningful value.

Example:

python
1result = None
2
3if result is None:
4    print("No result found")

Output:

text
1No result found

Use is None rather than == None when checking for None.

Type Checking with type()

The type() function tells you the type of an object.

python
1x = 100
2y = "Python"
3z = 5.6
4
5print(type(x))
6print(type(y))
7print(type(z))

Output:

text
1<class 'int'>
2<class 'str'>
3<class 'float'>

type() is particularly useful while learning Python and debugging code.

Type Checking with isinstance()

The isinstance() function checks whether an object is an instance of a particular type.

python
1age = 20
2
3print(isinstance(age, int))
4print(isinstance(age, float))

Output:

text
1True
2False

You can also check multiple types:

python
1value = 10
2
3print(isinstance(value, (int, float)))

Output:

text
1True

For many programs, isinstance() is preferable when you need to test whether a value belongs to a particular type.

Type Conversion in Python

Type conversion, also called type casting, means converting a value from one type to another.

Python provides built-in functions such as:

text
1int()
2float()
3str()
4bool()

Convert Integer to Float

python
1num = 10
2
3result = float(num)
4
5print(result)
6print(type(result))

Output:

text
110.0
2<class 'float'>

Convert Float to Integer

python
1price = 99.99
2
3result = int(price)
4
5print(result)

Output:

text
199

Be careful: int() truncates the fractional part. It does not round the value.

python
1print(int(9.99))
2print(int(-9.99))

Output:

text
19
2-9

Convert Integer to String

python
1age = 22
2
3age_text = str(age)
4
5print(age_text)
6print(type(age_text))

Output:

text
122
2<class 'str'>

This is useful when you need to combine numbers with text.

Convert String to Integer

If a string contains a valid integer representation, you can convert it using int().

python
1num = "150"
2
3number = int(num)
4
5print(number)
6print(type(number))

Output:

text
1150
2<class 'int'>

An invalid conversion raises an exception:

python
1num = "hello"
2
3number = int(num)

This results in a ValueError.

Convert String to Float

python
1price = "49.99"
2
3number = float(price)
4
5print(number)
6print(type(number))

Output:

text
149.99
2<class 'float'>

Boolean Conversion

The bool() function converts a value to a Boolean.

python
1print(bool(1))
2print(bool(0))
3print(bool(""))
4print(bool("Python"))

Output:

text
1True
2False
3False
4True

Some values are considered falsey, including:

python
1False
2None
30
40.0
5""
6[]
7{}
8set()

Most other objects are truthy.

This concept becomes important when writing conditions.

Taking User Input with input()

The input() function allows a Python program to receive text from the user.

Example:

python
1name = input("Enter your name: ")
2
3print("Hello", name)

If the user enters:

text
1Ankit

the program displays:

text
1Hello Ankit

Important: input() Returns a String

Regardless of what the user enters, input() returns a string.

python
1age = input("Enter your age: ")
2
3print(type(age))

Example output:

text
1<class 'str'>

If you need a number, explicitly convert the input.

python
1age = int(input("Enter your age: "))
2
3print(age + 5)

If the user enters:

text
122

the output is:

text
127

If the user enters something that cannot be converted to an integer, Python raises a ValueError.

Building a Simple Calculator

You can combine input(), float(), variables, and arithmetic operators to create a basic calculator.

python
1num1 = float(input("Enter first number: "))
2num2 = float(input("Enter second number: "))
3
4sum_result = num1 + num2
5
6print(f"Sum = {sum_result}")

Example:

text
1Enter first number: 10
2Enter second number: 5
3Sum = 15.0

Later in the course, you can improve this calculator by adding subtraction, multiplication, division, error handling, and a menu system.

Output Formatting in Python

Python provides several ways to format output.

Using Commas with print()

python
1name = "Ankit"
2age = 22
3
4print("Name:", name)
5print("Age:", age)

Output:

text
1Name: Ankit
2Age: 22

Using format()

Python's str.format() method can insert values into a string.

python
1name = "Ankit"
2age = 22
3
4print("My name is {} and I am {} years old.".format(name, age))

Output:

text
1My name is Ankit and I am 22 years old.

Using f-Strings

For modern Python code, f-strings are usually the clearest choice.

python
1name = "Ankit"
2age = 22
3
4print(f"My name is {name} and I am {age} years old.")

Output:

text
1My name is Ankit and I am 22 years old.

You can also evaluate expressions inside an f-string:

python
1price = 100
2quantity = 3
3
4print(f"Total = {price * quantity}")

Output:

text
1Total = 300

Formatting Decimal Numbers

You can control the number of decimal places with an f-string.

python
1pi = 3.14159265
2
3print(f"{pi:.2f}")

Output:

text
13.14

Another example:

python
1price = 1499.5678
2
3print(f"Price: ₹{price:.2f}")

Output:

text
1Price: ₹1499.57

Multiple Assignment

Python allows you to assign multiple values in a single statement.

python
1a, b, c = 10, 20, 30
2
3print(a)
4print(b)
5print(c)

Output:

text
110
220
330

This is called multiple assignment or iterable unpacking, depending on the context.

Assigning the Same Value

You can assign the same value to multiple names:

python
1x = y = z = 100
2
3print(x)
4print(y)
5print(z)

Output:

text
1100
2100
3100

Each name refers to the same integer object in this example.

Swapping Variables in Python

Python provides a simple and elegant way to swap two variables.

Pythonic Approach

python
1a = 10
2b = 20
3
4a, b = b, a
5
6print(a)
7print(b)

Output:

text
120
210

This is the preferred approach in normal Python code.

Using a Temporary Variable

The traditional approach uses a temporary variable.

python
1a = 10
2b = 20
3
4temp = a
5a = b
6b = temp
7
8print(a)
9print(b)

Output:

text
120
210

Arithmetic Swap

You may also encounter an arithmetic approach:

python
1a = 10
2b = 20
3
4a = a + b
5b = a - b
6a = a - b
7
8print(a)
9print(b)

Output:

text
120
210

Although this works for suitable numeric values, it is generally less readable than Python's multiple-assignment syntax. Prefer:

python
1a, b = b, a

in normal Python programs.

Practical Project: Student Information Program

Let's combine variables, strings, integers, Boolean values, input, and f-strings.

python
1name = input("Enter your name: ")
2age = int(input("Enter your age: "))
3city = input("Enter your city: ")
4course = input("Enter your course: ")
5
6is_student = True
7
8print("\nStudent Information")
9print("-------------------")
10print(f"Name: {name}")
11print(f"Age: {age}")
12print(f"City: {city}")
13print(f"Course: {course}")
14print(f"Student: {is_student}")

Example:

text
1Enter your name: Ankit
2Enter your age: 22
3Enter your city: Delhi
4Enter your course: Python
5
6Student Information
7-------------------
8Name: Ankit
9Age: 22
10City: Delhi
11Course: Python
12Student: True

This example combines several concepts from this lesson into one practical program.

Common Beginner Mistakes

Mistake 1: Starting a Variable With a Number

Incorrect:

python
12name = "Ankit"

Correct:

python
1name2 = "Ankit"

Mistake 2: Using a Hyphen

Incorrect:

python
1student-name = "Ankit"

Correct:

python
1student_name = "Ankit"

Mistake 3: Using a Keyword

Incorrect:

python
1class = "Python"

Correct:

python
1class_name = "Python"

Mistake 4: Forgetting That input() Returns a String

Incorrect:

python
1age = input("Enter age: ")
2
3print(age + 5)

Correct:

python
1age = int(input("Enter age: "))
2
3print(age + 5)

Mistake 5: Expecting int() to Round a Number

python
1print(int(9.99))

Output:

text
19

int() removes the fractional part; it does not round to the nearest integer.

Module Summary

In this lesson, you learned how Python variables and data types work.

You learned:

What Python variables are
Variable assignment
Variable naming rules
Naming conventions
Dynamic typing
Python constants
Object references
Mutable objects
The id() function
Numeric data types
Integers
Floating-point numbers
Complex numbers
Boolean values
Strings
String indexing
String length
String concatenation
String repetition
None
type()
isinstance()
Type conversion
int()
float()
str()
bool()
input()
Output formatting
f-strings
Multiple assignment
Variable swapping

These concepts are essential for understanding more advanced Python topics such as operators, conditional statements, loops, functions, collections, and object-oriented programming.

Practice Exercises

Exercise 1: Personal Information

Create variables for:

Name
Age
City
Programming language

Print all values.

Exercise 2: Data Types

Create one variable for each of these types:

text
1int
2float
3complex
4bool
5str
6NoneType

Use type() to display their types.

Exercise 3: Type Conversion

Convert:

text
1integer → float
2float → integer
3integer → string
4string → integer
5string → float

Print both the converted value and its type.

Exercise 4: User Input

Ask the user for:

Name
Age
City

Display the information using an f-string.

Exercise 5: Calculator

Ask the user for two numbers and display:

Sum
Difference
Product
Division
Remainder

Exercise 6: Variable Swap

Create two variables and swap their values using:

python
1a, b = b, a

Exercise 7: String Operations

Create a string and demonstrate:

Indexing
len()
Concatenation
Repetition

Exercise 8: Student Profile

Build a small student profile application that accepts user input and displays a formatted profile.

Quiz

Question 1

Which symbol is used for assignment in Python?

A. == B. = C. => D. :=

Answer: B. =

Question 2

Which data type represents whole numbers?

A. float B. str C. int D. bool

Answer: C. int

Question 3

What does input() return?

A. Always an integer B. Always a float C. A string D. A Boolean

Answer: C. A string

Question 4

Which is a valid Python variable?

A. 2name B. student-name C. student_name D. class

Answer: C. student_name

Question 5

What is the type of 3.14?

A. int B. float C. complex D. str

Answer: B. float

Question 6

What does None represent?

A. Zero B. False C. An empty string D. Absence of a value

Answer: D. Absence of a value

Question 7

What is the recommended Pythonic way to swap two variables?

python
1a, b = b, a

Question 8

Which function checks whether an object is an instance of a particular type?

python
1isinstance()

What's Next?

In the next lesson, you will learn about Python Operators.

You will explore:

Arithmetic operators
Assignment operators
Comparison operators
Logical operators
Identity operators
Membership operators
Bitwise operators
Operator precedence
Practical expressions and examples