Python Practical Guide: File I/O, CSV, JSON, HTTP Requests, SQLite, Scheduling, Logging, Argument Parsing, Compression, Subprocess, DateTime, Email, Image Processing, NumPy, Pandas, Regex, System Info, Socket Programming, and AsyncIO

1. File read/write:

with open('file.txt','r') as file:
    content = file.read()
print(content)

and

with open('output.txt','w') as file:
    file.write("Hello, World!")

2. CSV handling: read with

import csv
with open('data.csv','r') as file:
    reader = csv.reader(file)
    for row in reader:
        print(row)

; write with

import csv
data = [['Name','Age'],['Alice',30],['Bob',25]]
with open('output.csv','w', newline='') as file:
    writer = csv.writer(file)
    writer.writerows(data)

3. JSON handling: read with

import json
with open('data.json','r') as file:
    data = json.load(file)
print(data)

; write with

import json
data = {'name':'Alice','age':30}
with open('output.json','w') as file:
    json.dump(data, file)

4. HTTP requests: GET with

import requests
response = requests.get('https://api.example.com/data')
if response.status_code == 200:
    print(response.json())
else:
    print(f"Request failed with status code: {response.status_code}")

; POST with

import requests
payload = {'key':'value'}
response = requests.post('https://api.example.com/submit', data=payload)
if response.status_code == 200:
    print(response.json())
else:
    print(f"Request failed with status code: {response.status_code}")

5. SQLite database:

import sqlite3
conn = sqlite3.connect('example.db')
c = conn.cursor()
c.execute('''CREATE TABLE IF NOT EXISTS stocks (date text, trans text, symbol text, qty real, price real)''')
c.execute("INSERT INTO stocks VALUES ('2023-01-01','BUY','RHAT',100,35.14)")
conn.commit()
c.execute('SELECT * FROM stocks')
print(c.fetchall())
conn.close()

6. Scheduling tasks:

import schedule, time

def job():
    print("I'm working...")

schedule.every(10).seconds.do(job)
while True:
    schedule.run_pending()
    time.sleep(1)

7. Logging:

import logging
logging.basicConfig(filename='app.log', level=logging.INFO, format='%(asctime)s - %(levelname)s - %(message)s')
logging.info('This is an info message')
logging.warning('This is a warning message')
logging.error('This is an error message')

8. Command‑line argument parsing:

import argparse
parser = argparse.ArgumentParser(description='Process some integers.')
parser.add_argument('integers', metavar='N', type=int, nargs='+', help='an integer for the accumulator')
parser.add_argument('--sum', dest='accumulate', action='store_const', const=sum, default=max, help='sum the integers (default: find the max)')
args = parser.parse_args()
print(args.accumulate(args.integers))

9. File compression:

import zipfile
with zipfile.ZipFile('archive.zip','w') as zipf:
    zipf.write('file.txt')

; extraction with

import zipfile
with zipfile.ZipFile('archive.zip','r') as zipf:
    zipf.extractall('.')

10. Subprocess execution:

import subprocess
result = subprocess.run(['ls','-l'], capture_output=True, text=True)
print(result.stdout)

11. Date and time:

from datetime import datetime
now = datetime.now()
print(now.strftime("%Y-%m-%d %H:%M:%S"))

12. Sending email:

import smtplib
from email.mime.text import MIMEText
msg = MIMEText('This is the body of the email')
msg['Subject'] = 'Hello'
msg['From'] = '[email protected]'
msg['To'] = '[email protected]'
with smtplib.SMTP('smtp.example.com', 587) as server:
    server.starttls()
    server.login('username','password')
    server.sendmail('[email protected]',["[email protected]"],msg.as_string())

13. Image processing:

from PIL import Image
img = Image.open('image.jpg')
img_resized = img.resize((800,600))
img_resized.save('resized_image.jpg')

14. Text replace:

text = "Hello, World!"
new_text = text.replace("World","Python")
print(new_text)

15. Numerical computation with NumPy:

import numpy as np
arr = np.array([1,2,3,4])
print(arr * 2)

16. Data analysis with Pandas:

import pandas as pd
df = pd.DataFrame({
    'Name': ['Alice','Bob','Charlie'],
    'Age': [25,30,35]
})
print(df.describe())

17. Regular expressions:

import re
pattern = r'\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Z|a-z]{2,}\b'
text = "Contact us at [email protected]"
match = re.search(pattern, text)
if match:
    print(match.group())

18. System information:

import platform
print(platform.system())
print(platform.release())
print(platform.version())

19. Simple TCP server:

import socket
host = '127.0.0.1'
port = 65432
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
    s.bind((host, port))
    s.listen()
    conn, addr = s.accept()
    with conn:
        print('Connected by', addr)
        while True:
            data = conn.recv(1024)
            if not data:
                break
            conn.sendall(data)

20. Simple TCP client:

import socket
host = '127.0.0.1'
port = 65432
with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
    s.connect((host, port))
    s.sendall(b'Hello, Server!')
    data = s.recv(1024)
print('Received', repr(data))

21. Asynchronous programming with asyncio:

import asyncio
async def my_coroutine():
    print("Starting coroutine")
    await asyncio.sleep(1)
    print("Coroutine finished")
async def main():
    task = asyncio.create_task(my_coroutine())
    await task
asyncio.run(main())