Python Data Types Reference Guide

1. The 12 Core Python Data Types

Python provides a rich set of built-in data types to store various kinds of information efficiently.

1. Integer (int)

Whole numbers (no decimals).

age = 25
print(type(age)) # <class 'int'>
print(age)       # 25

2. Float (float)

Decimal/fractional numbers.

pi = 3.14159
print(type(pi))  # <class 'float'>
print(pi)        # 3.14159

3. String (str)

Text / sequence of characters.

name = "Python"
print(type(name))# <class 'str'>
print(name)      # Python

4. Boolean (bool)

Truth values (True or False).

is_active = True
print(type(is_active)) # <class 'bool'>
print(is_active)       # True

5. List

Ordered, mutable collection.

fruits = ["Apple", "Banana"]
print(type(fruits)) # <class 'list'>
print(fruits)       # ['Apple', 'Banana']

6. Tuple

Ordered, immutable collection.

coords = (10, 20, 30)
print(type(coords)) # <class 'tuple'>
print(coords)       # (10, 20, 30)

7. Set

Unordered collection of unique items.

colors = {"red", "green"}
print(type(colors)) # <class 'set'>
print(colors)       # {'red', 'green'}

8. Dictionary (dict)

Key-value pair mappings.

student = {"name": "Alice", "age": 20}
print(type(student)) # <class 'dict'>
print(student)       # {'name': 'Alice'...}

9. Complex (complex)

Numbers with real & imaginary parts.

c = 2 + 3j
print(type(c)) # <class 'complex'>
print(c)       # (2+3j)

10. Bytes (bytes)

Immutable binary data sequence.

data = b"Python"
print(type(data)) # <class 'bytes'>
print(data)       # b'Python'

11. Bytearray (bytearray)

Mutable binary data sequence.

data = bytearray(5)
print(type(data)) # <class 'bytearray'>

12. NoneType (None)

Represents absence of a value.

x = None
print(type(x)) # <class 'NoneType'>
print(x)       # None

2. Variables, Scope & Operations

Assigning Multiple Variables

# Same value
a = b = c = 100

# Different values
x, y, z = 10, 20, 30

# Variable swapping
m, n = 5, 10
m, n = n, m  # m becomes 10, n becomes 5

Variable Scope (Global vs Local)

x = "Global"  # Global variable

def func():
    y = "Local"  # Local variable
    print("Inside function, y =", y)

func()
print("Outside function, x =", x)

Type Conversion & Common Functions

x = "100"
print(int(x) + 50)  # Output: 150

y = 3.99
print(int(y))       # Output: 3 (truncates decimal)

flag = "True"
print(bool(flag))   # Output: True

Supported casting functions: int(), float(), str(), bool(), list(), tuple(), dict()

Constants & Variable Management

PI = 3.14159  # Constant by convention (UPPERCASE)

a = 10
del a         # Deletes variable from memory

# Checking if variable exists
if 'x' in globals():
    print("x exists")

Note: Python does not enforce rigid hardware constants, but using uppercase names signals to other developers that a variable value should remain constant.