Python Basics — Numbers

Numbers

Python has three numeric types: integers, floating-point numbers, and complex numbers. Most of the time, you’ll work with integers and floats.

Integers (int)

Integers are whole numbers — positive, negative, or zero — with no decimal point.

age = 25
temperature = -10
count = 0
big_number = 1_000_000  # Underscores for readability

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

Python integers have unlimited precision — they can be as large as your memory allows:

huge = 10 ** 100  # 10 raised to the power of 100
print(huge)
# 10000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
print(type(huge))  # <class 'int'>

Integer Bases

decimal = 42        # Base 10 (default)
binary = 0b101010   # Base 2 (prefix 0b)
octal = 0o52        # Base 8 (prefix 0o)
hexadecimal = 0x2A  # Base 16 (prefix 0x)

print(decimal, binary, octal, hexadecimal)
# 42 42 42 42 — all represent the same number!

Floating-Point Numbers (float)

Floats are numbers with a decimal point:

price = 19.99
pi = 3.14159
negative = -0.5
scientific = 2.5e3  # 2.5 × 10³ = 2500.0

print(type(price))  # <class 'float'>

Float Precision Warning

Floats have limited precision due to how computers store decimal numbers in binary:

print(0.1 + 0.2)       # 0.30000000000000004 (not 0.3!)
print(0.1 + 0.2 == 0.3) # False

How to handle this: Use round() or the decimal module for precise calculations:

# Using round()
result = round(0.1 + 0.2, 1)
print(result)        # 0.3
print(result == 0.3) # True

# Using decimal module for financial calculations
from decimal import Decimal
a = Decimal("0.1")
b = Decimal("0.2")
print(a + b)  # 0.3 (exact!)

Complex Numbers (complex)

Complex numbers have a real part and an imaginary part:

z = 3 + 4j
print(z)          # (3+4j)
print(type(z))    # <class 'complex'>
print(z.real)     # 3.0
print(z.imag)     # 4.0

You probably won’t use complex numbers unless you’re working in scientific computing or engineering.

Numeric Type Comparison

Type	Example	Use Case
int	42, -7, 0	Counting, indexing, IDs
float	3.14, -0.5, 2.5e3	Measurements, calculations
complex	3+4j	Scientific computing

The math Module

Python’s built-in math module provides mathematical functions:

import math

print(math.sqrt(16))      # 4.0 — square root
print(math.ceil(4.2))     # 5 — round up
print(math.floor(4.8))    # 4 — round down
print(math.pow(2, 10))    # 1024.0 — power
print(math.pi)            # 3.141592653589793
print(math.e)             # 2.718281828459045
print(math.factorial(5))  # 120 — 5! = 5×4×3×2×1
print(math.log(100, 10))  # 2.0 — log base 10 of 100
print(math.gcd(12, 18))   # 6 — greatest common divisor

The random Module

Generate random numbers with the random module:

import random

print(random.randint(1, 10))     # Random integer from 1 to 10
print(random.random())           # Random float from 0.0 to 1.0
print(random.uniform(1.0, 5.0))  # Random float from 1.0 to 5.0
print(random.choice([1, 2, 3]))  # Random element from a list

# Shuffle a list in place
cards = [1, 2, 3, 4, 5]
random.shuffle(cards)
print(cards)  # e.g., [3, 1, 5, 2, 4]

Built-in Numeric Functions

Function	Description	Example
abs(x)	Absolute value	abs(-5) → 5
round(x, n)	Round to n decimals	round(3.14159, 2) → 3.14
pow(x, y)	x to the power of y	pow(2, 3) → 8
divmod(x, y)	Quotient and remainder	divmod(17, 5) → (3, 2)
min(...)	Minimum value	min(3, 1, 4) → 1
max(...)	Maximum value	max(3, 1, 4) → 4
sum(iterable)	Sum of elements	sum([1, 2, 3]) → 6

Number Formatting

price = 1234567.891

# Comma separator
print(f"{price:,.2f}")  # 1,234,567.89

# Percentage
rate = 0.856
print(f"{rate:.1%}")  # 85.6%

# Padding with zeros
code = 42
print(f"{code:05}")  # 00042

# Binary, octal, hex
num = 255
print(f"{num:b}")   # 11111111
print(f"{num:o}")   # 377
print(f"{num:x}")   # ff
print(f"{num:X}")   # FF

Common Mistakes

Mistake	Example	Fix
Integer division surprise	7 / 2 → 3.5 (not 3)	Use // for integer division
Float comparison	0.1 + 0.2 == 0.3 → False	Use round() or math.isclose()
Division by zero	10 / 0 → ZeroDivisionError	Check divisor before dividing
String + number	"Age: " + 25 → TypeError	Use f-string: f"Age: {25}"

Summary

• Integers (int) handle whole numbers with unlimited precision
• Floats (float) handle decimal numbers but have precision limitations
• Complex (complex) numbers have real and imaginary parts
• Use the math module for mathematical functions (sqrt, ceil, floor)
• Use the random module for generating random numbers
• Format numbers with f-strings for commas, percentages, and padding
• Be careful with float comparisons — use round() or math.isclose()

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