Python Data Types

What are data types in Python?

A data type describes the kind of value an object represents and the operations that can be performed on it. Python is dynamically typed, so you do not declare a variable's type before assigning a value. Python determines the type at runtime.

value = 10

print(value)
print(type(value))

Output

In this example, value refers to an integer object. The type() function reports the object's class.

Built-in Python data types

Python includes built-in types for numbers, text, collections, Boolean values, binary data, and missing values:

In Python, everything is an object. A variable is a name that refers to an object, and that object has a type.

Numeric types

int stores whole numbers, float stores decimal values, and complex stores a real part and an imaginary part. Python integers can grow as large as available memory allows.

whole = 42
decimal = 3.14
complex_value = 2 + 5j

print(type(whole))
print(type(decimal))
print(type(complex_value))

Output

Sequence types

Sequence types store items in an order. Lists are mutable, tuples are immutable, strings contain text, and ranges represent a sequence of numbers without storing every number separately.

items = ["Python", 3, True]       # list
coordinates = (10, 20)           # tuple
language = "Python"              # string
numbers = range(1, 4)             # range

print(items)
print(coordinates)
print(language)
print(list(numbers))

Output

Use a list when values need to change, and use a tuple when the group of values should remain fixed.

Set types

A set stores unique values and can be changed. A frozenset also stores unique values, but it cannot be changed after creation. Sets do not support indexing, and their display order should not be relied upon.

languages = {"Python", "Java", "Python"}
fixed_languages = frozenset(["Python", "Java"])

print(len(languages))
print(type(fixed_languages))

Output

Dictionary type

A dictionary stores data as key-value pairs. Keys must be unique and hashable. Dictionaries preserve insertion order in modern Python versions and are useful for named data.

student = {
    "name": "Asha",
    "age": 20,
    "course": "Python"
}

print(student["name"])
print(type(student))

Output

Boolean and None types

bool has only two values: True and False. The special value None means that a value is absent or not available. These values are commonly used in conditions and function results.

is_logged_in = True
profile = None

print(is_logged_in)
print(profile is None)

Output

Binary data types

bytes is an immutable sequence of integers from 0 to 255. bytearray is its mutable counterpart, while memoryview provides access to binary data without making an unnecessary copy.

data = bytes([65, 66, 67])
mutable_data = bytearray(data)
mutable_data[0] = 90

print(data)
print(mutable_data)

Output

Checking and comparing types

Use type() when you need the exact type. Use isinstance() when you want to check whether an object belongs to a type or one of its subclasses.

age = 21

print(type(age) is int)
print(isinstance(age, int))

Output

Type conversion

Type conversion creates a value of another type. Python performs some conversions automatically, such as converting an integer to a float during mixed arithmetic. You can request a conversion explicitly with functions such as int(), float(), str(), list(), and tuple().

price = 19
decimal_price = float(price)
number_text = str(price)

print(decimal_price)
print(number_text, type(number_text))

Output

Conversions can fail or lose information. For example, int(7.9) removes the fractional part, and int("hello") raises ValueError.

Key points for beginners

• Python assigns types at runtime; variable declarations do not need a type keyword.
• Lists, dictionaries, sets, and bytearrays are mutable; strings, tuples, bytes, and frozensets are immutable.
• Use isinstance() for readable type checks in application code.
• Use None to represent an intentionally missing value and compare it with is None.
• Choose a data type based on the operations and behavior your program needs.