Common Operations with Python's os, sys, and datetime Modules

os module

import os

print(os.listdir('.'))

# lists files and sub‑directories in the current directory

Expected output: a list such as ['file1.txt', 'folder1', 'file2.py'] os.makedirs('new_folder/subfolder') # creates a multi‑level directory

Expected output: no direct output; a folder new_folder/subfolder is created. os.rmdir('new_folder') # removes an empty directory

Expected output: no direct output; the empty new_folder is deleted. print(os.getcwd()) # prints the current working directory

Expected output: a path such as

/Users/username/Documents/Projects

os.chdir('/home/user')

# changes the current working directory

sys module print(sys.version) Expected output: the Python interpreter version string, e.g.,

3.9.1 (tags/v3.9.1:1e5d33e, Dec 7 2020, 17:08:21) [MSC v.1927 64 bit (AMD64)]

import sys

print(sys.argv)

# prints script name and command‑line arguments

Expected output: a list like ['script.py', 'arg1', 'arg2'] when run with arguments. sys.exit(0) # exits the program with status code 0

Expected output: program terminates and returns exit code 0 to the OS. sys.path.append('/my/custom/path') # adds a directory to the module search path

Expected output: no direct output; subsequent import statements will search the new path. print(sys.ps1) # prints the current interactive prompt (default >>>) sys.ps1 = '> ' # changes the prompt

Expected output: first shows the default prompt, then the prompt changes to > in interactive mode.

datetime module

from datetime import datetime

print(datetime.now())

Expected output: current date‑time, e.g.,

2024-05-11 10:30:45.123456

now = datetime.now()

print(now.strftime('%Y-%m-%d %H:%M:%S'))

Expected output: formatted date‑time string like

2024-05-11 10:30:45

one_week_later = datetime.now() + timedelta(weeks=1)

print(one_week_later)

Expected output: date‑time one week ahead, e.g.,

2024-05-18 10:30:45.123456

date_string = '2024-06-01'

parsed_date = datetime.strptime(date_string, '%Y-%m-%d')

print(parsed_date)

Expected output:

2024-06-01 00:00:00

from datetime import datetime, timedelta

start = datetime(2024, 5, 1)

end = datetime(2024, 5, 11)

delta = end - start

print(delta.days)

Expected output: 10, the number of days between the two dates.