Functions in Modules
M3-R5.1 · Chapter 6: Functions · 3 min read
2. Functions in Module
1. What is a Module?
A module is a file containing Python definitions (functions, classes, variables) that can be imported and reused in other programs. Python ships with a rich standard library of built-in modules, and you can also install third-party modules via pip.
Key benefits:
• Code reusability — write once, use anywhere
• Organisation — split large programs into logical files
• Namespace management — avoids name conflicts
• Access to Python's standard library (~200+ built-in modules)
2. Ways to Import a Module
|
Syntax |
Meaning |
Example usage |
|
import module |
Import whole module |
import math |
|
from module import name |
Import specific item |
from math import sqrt |
|
from module import * |
Import everything (avoid in big projects) |
from math import * |
|
import module as alias |
Give module a short alias |
import math as m |
3. math Module — Complete Function Reference
Provides mathematical functions and constants for numerical computations. Always use import math before calling any function.
Usage: import math then call math.sqrt(25)
|
Function / Constant |
Description |
Example |
Result |
|
math.pi |
Value of π (constant) |
math.pi |
3.14159… |
|
math.e |
Euler's number (constant) |
math.e |
2.71828… |
|
math.sqrt(x) |
Square root of x |
math.sqrt(25) |
5.0 |
|
math.pow(x, y) |
x raised to power y |
math.pow(2, 8) |
256.0 |
|
math.floor(x) |
Largest integer ≤ x |
math.floor(4.9) |
4 |
|
math.ceil(x) |
Smallest integer ≥ x |
math.ceil(4.1) |
5 |
|
math.fabs(x) |
Absolute value (float) |
math.fabs(-7) |
7.0 |
|
math.factorial(n) |
n! factorial |
math.factorial(5) |
120 |
|
math.gcd(a, b) |
Greatest common divisor |
math.gcd(12, 8) |
4 |
|
math.log(x) |
Natural log (base e) |
math.log(math.e) |
1.0 |
|
math.exp(x) |
e raised to power x |
math.exp(1) |
2.718… |
|
math.hypot(x, y) |
Hypotenuse √(x²+y²) |
math.hypot(3, 4) |
5.0 |
|
math.isnan(x) |
True if x is NaN |
math.isnan(float('nan')) |
True |
|
math.trunc(x) |
Truncate to integer |
math.trunc(3.99) |
3 |
4. random Module — Complete Function Reference
Generates pseudo-random numbers, selections, and shuffles. Uses the Mersenne Twister algorithm internally. Set a seed for reproducible results.
Usage: import random then call random.randint(1, 10)
|
Function |
Description |
Example |
Result |
|
random.random() |
Float in [0.0, 1.0) |
random.random() |
0.7342… |
|
random.randint(a, b) |
Integer in [a, b] inclusive |
random.randint(1, 6) |
4 |
|
random.randrange(start, stop, step) |
Random from range |
random.randrange(0, 10, 2) |
6 |
|
random.choice(seq) |
Random element from sequence |
random.choice([1,2,3]) |
2 |
|
random.choices(seq, k=n) |
k random choices with replacement |
random.choices('abc', k=3) |
['b','a','b'] |
|
random.shuffle(lst) |
Shuffle list in-place |
random.shuffle([1,2,3]) |
[3,1,2] |