Python basics - Day 20

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Day 20 – Python Standard Library

Project: Build a “Utility Toolkit” using core Python standard modules (math, random, datetime, time, os).

01. Learning Goal

By the end of this lesson, you will be able to:

Use Python’s built-in standard libraries effectively
Perform mathematical operations with math
Generate random numbers with random
Work with dates and time using datetime and time
Manage files and folders with os

02. Problem Scenario

You’re developing a small automation program and need tools for math calculations, random data generation, time management, and file handling — all without installing extra libraries.

Luckily, Python’s Standard Library already provides everything you need.

03. Step 1 – math module (Mathematical Operations)

Provides mathematical functions like square roots, powers, factorials, and constants such as π.

import math

print(math.sqrt(16))    # Square root
print(math.pow(2, 3))   # Power
print(math.factorial(5)) # Factorial
print(math.pi)          # Pi constant

print(math.ceil(3.2))   # Ceiling (round up)
print(math.floor(3.9))  # Floor (round down)

04. Step 2 – random module (Random Number Generation)

Generate random integers, choices, or samples — useful for games, simulations, and testing.

import random

print(random.randint(1, 6))               # Random integer (1–6)
print(random.choice(["Apple", "Banana", "Grape"]))  # Random choice
print(random.sample(range(1, 46), 6))    # Lotto numbers

05. Step 3 – datetime module (Date and Time Handling)

Work with current dates, format conversions, and time calculations.

from datetime import datetime, timedelta

now = datetime.now()
print("Now:", now)

d = datetime(2025, 1, 1, 9, 0)
print("Specific Date:", d)

tomorrow = now + timedelta(days=1)
print("Tomorrow:", tomorrow)

date_str = "2025-09-11 18:30"
dt = datetime.strptime(date_str, "%Y-%m-%d %H:%M")
print("Parsed:", dt)

print(dt.strftime("%Y-%m-%d %H:%M"))
print(dt.strftime("%Y년 %m월 %d일 %H시 %M분"))

06. Step 4 – time module (Delay and Execution Control)

Pause your program or measure execution duration.

import time

print("Wait 3 seconds...")
time.sleep(3)
print("Done!")

07. Step 5 – os module (Operating System Interaction)

Manage files, folders, and paths.

import os

print("Current Working Directory:", os.getcwd())
os.mkdir("test_folder")
os.rmdir("test_folder")

08. Step 6 – Practice Examples

Example 1: Circle Area Calculator

import math

r = 5
area = math.pi * r**2
print("Circle Area:", area)

Example 2: Lotto Number Generator

import random

lotto = random.sample(range(1, 46), 6)
print("Lotto Numbers:", lotto)

Example 3: Today’s Date Formatter

from datetime import datetime

today = datetime.today()
print("Today:", today.strftime("%Y-%m-%d"))

09. Step 7 – Mini Project: Utility Toolkit

Combine all modules into one useful “Utility Toolkit”.

import math, random, time, os
from datetime import datetime

print("--- Utility Toolkit ---")

# 1. Math
r = 4
print("Circle Area:", math.pi * r**2)

# 2. Random
numbers = random.sample(range(1, 46), 6)
print("Random Numbers:", numbers)

# 3. Date & Time
print("Now:", datetime.now().strftime("%Y-%m-%d %H:%M"))

# 4. Delay Example
print("Processing...")
time.sleep(2)
print("Done!")

# 5. OS
print("Current Folder:", os.getcwd())

Output example:

--- Utility Toolkit ---
Circle Area: 50.26548245743669
Random Numbers: [8, 21, 34, 45, 12, 3]
Now: 2025-10-04 16:10
Processing...
Done!
Current Folder: /Users/sabin/projects

10. Reflection

You have learned how to: