Standard Modules in Python: math, datetime, and os

Python follows a “Batteries Included” philosophy — it comes pre-installed with rich standard modules so programmers don’t have to write common utilities from scratch. Three of the most important standard modules in the BCA syllabus are math, datetime, and os.

Core Standard Modules in Unit 3

1. math Module

Mathematical functions (square root, trigonometry, logarithms, constants like pi and e).

2. datetime Module

Working with dates, times, timestamps, formatting (strftime), and date arithmetic.

3. os Module

Interacting with the Operating System (folders, file paths, environment variables).

1. The math Module

The math module provides fast mathematical functions and constants. To use it, write import math.

Important Constants in `math`:

math.pi → Value of Pi (3.141592653589793)
math.e → Euler’s number (2.718281828459045)

Important Functions in `math`:

Function	Description	Example	Output
`math.sqrt(x)`	Returns the square root of `x` as a `float`	`math.sqrt(49)`	`7.0`
`math.pow(x, y)`	Returns `x` raised to power `y` as a `float`	`math.pow(2, 5)`	`32.0`
`math.ceil(x)`	Rounds a float UP to the nearest integer	`math.ceil(4.2)`	`5`
`math.floor(x)`	Rounds a float DOWN to the nearest integer	`math.floor(4.8)`	`4`
`math.factorial(x)`	Returns the factorial of `x` (`x!`)	`math.factorial(5)`	`120`
`math.gcd(a, b)`	Returns Greatest Common Divisor of `a` & `b`	`math.gcd(12, 18)`	`6`
`math.fabs(x)`	Returns the absolute (positive) float value	`math.fabs(-15.5)`	`15.5`
`math.sin(x)`, `cos(x)`	Trigonometric functions (`x` in radians)	`math.sin(math.radians(90))`	`1.0`
`math.log10(x)`	Base-10 logarithm of `x`	`math.log10(1000)`	`3.0`

import math

radius = 7
area = math.pi * math.pow(radius, 2)
print("Area of circle =", round(area, 2))   # Output: 153.94
print("Ceiling of 9.1 =", math.ceil(9.1))   # Output: 10
print("Floor of 9.9   =", math.floor(9.9))  # Output: 9
print("5!             =", math.factorial(5))# Output: 120

2. The datetime Module

The datetime module provides classes for manipulating dates and times in both simple and complex ways.

Main Classes Inside `datetime` Module:

datetime.date — Represents a calendar date (year, month, day).
datetime.time — Represents time of day (hour, minute, second, microsecond).
datetime.datetime — Combines both date and time into a single object.
datetime.timedelta — Represents the difference (duration) between two dates or times (used for adding/subtracting days).

Practical Examples of `datetime`:

from datetime import datetime, date, timedelta

# 1. Get current date and time
now = datetime.now()
print("Current Date & Time:", now)

# 2. Get only today's date
today = date.today()
print("Year:", today.year, "Month:", today.month, "Day:", today.day)

# 3. Create a specific custom date (e.g., Independence Day)
ind_day = date(1947, 8, 15)
print("Custom Date:", ind_day)

# 4. Date Arithmetic using timedelta (Add 7 days to today)
next_week = today + timedelta(days=7)
print("Date after 7 days:", next_week)

Formatting Dates with `strftime()` (String Format Time):

The strftime() method converts a datetime object into a readable formatted string:

%d → Day of month (01 to 31)
%m → Month number (01 to 12)
%B → Full month name (April, October)
%Y → 4-digit Year (2026)
%A → Full weekday name (Monday, Friday)
%H:%M:%S → 24-hour Time (14:30:05)

from datetime import datetime

now = datetime.now()
formatted = now.strftime("%d-%B-%Y (%A) %H:%M:%S")
print("Formatted:", formatted)
# Example Output: 02-April-2026 (Thursday) 18:45:10

3. The os Module (Operating System Interface)

The os module allows your Python program to interact directly with the underlying Operating System (Windows, Linux, macOS) to manage directories (folders), files, paths, and environment variables.

Important Functions in `os`:

Function	Description
`os.name`	Returns the OS kernel name (`'nt'` for Windows, `'posix'` for Linux/Mac)
`os.getcwd()`	Returns the Current Working Directory (folder path)
`os.chdir(path)`	Changes the current working directory to `path`
`os.listdir(path)`	Returns a list of all files and folders inside `path`
`os.mkdir("folder")`	Creates a single new folder (directory)
`os.makedirs("a/b/c")`	Creates nested folders recursively
`os.rmdir("folder")`	Removes an empty directory
`os.remove("file.txt")`	Deletes a file from the disk
`os.rename(old, new)`	Renames a file or folder from `old` to `new`
`os.path.exists(path)`	Returns `True` if the file or folder exists, else `False`

import os

# 1. Check current working directory
print("Current Folder:", os.getcwd())

# 2. Create a new folder if it doesn't exist
if not os.path.exists("BCA_Notes"):
    os.mkdir("BCA_Notes")
    print("Folder 'BCA_Notes' created successfully!")

# 3. List all files and folders in current directory
print("Files in current directory:", os.listdir("."))

Standard Modules in Python: os, datetime & math Modules

Standard Modules in Python: math, datetime, and os

1. The math Module

Important Constants in math:

Important Functions in math:

2. The datetime Module

Main Classes Inside datetime Module:

Practical Examples of datetime:

Formatting Dates with strftime() (String Format Time):