Python Numbers

Three Numeric Types in Python

Python has three built-in numeric types:

• int — Whole numbers, positive or negative, with no decimal point and unlimited length.
• float — Floating-point numbers containing one or more decimals (including scientific notation).
• complex — Numbers written with a j as the imaginary part (mostly used in engineering and higher math).

x = 25
y = -3.5
z = 4 + 2j

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

25 <class 'int'>
-3.5 <class 'float'>
(4+2j) <class 'complex'>

Integers (int)

An integer (int) is any whole number without decimals—positive, negative, or zero. Python integers can be arbitrarily large!

score = 100
temperature = -12
population = 8000000000

print(score, temperature, population)

100 -12 8000000000

Floating-Point Numbers (float)

A float represents real numbers with a decimal point. You can also write floats using scientific notation with e or E to indicate powers of 10 (for instance, 2.5e3 means 2.5 × 1000 = 2500.0).

price = 19.99
tiny = -0.005
big_float = 3.5e4

print(price, tiny, big_float)
print(type(big_float))

19.99 -0.005 35000.0
<class 'float'>

Complex Numbers (Basic Introduction)

In Python, complex numbers combine a real part and an imaginary part marked with the letter j (not i). While beginners mainly use int and float, knowing complex exists prevents confusion when you see j in math libraries.

Numeric Type Conversion

You can convert integers and floats between types using int(), float(), and complex(). Note that you cannot convert a complex number directly into an int or float.

a = 10
b = 4.8

a_float = float(a)
b_int = int(b)
a_complex = complex(a)

print(a_float)
print(b_int)
print(a_complex)

10.0
4
(10+0j)

z = 3 + 4j
print(int(z))

z = 3 + 4j
print(int(z.real))

Random Numbers (Basic Introduction)

Python includes a built-in random module for generating unpredictable numbers—useful in games, quizzes, and simulations.

Use import random at the top of your file, then call random.randint(start, end) to get a random integer between start and end (inclusive).

import random

random.seed(42)
dice_roll = random.randint(1, 6)
lucky_num = random.randrange(10, 50, 5)

print("Dice roll:", dice_roll)
print("Random multiple of 5:", lucky_num)

Dice roll: 6
Random multiple of 5: 15

Quick Check

Chapter Summary

• Python supports int (whole numbers), float (decimal or scientific numbers), and complex (with j).
• int(), float(), and complex() convert between compatible numeric types.
• import random unlocks functions like random.randint(a, b) for beginner games and experiments.