last-day
core conepts
"""
=======================================================
CORE PYTHON BASICS
=======================================================
"""
# 🔹 Variables & Data Types
# What: It Store values (numbers, text, flags)
# Why: Needed for all scripts, from configs to counters
# How:
server_count = 5 # int
server_name = "web-01" # str
is_active = True # bool
cpu_usage = 75.5 # float
print(server_count, server_name, is_active, cpu_usage)
print(f"count = {server_count}, name = {server_name}, active = {is_active}, cpu = {cpu_usage}")
# 🔹 Loops
# What: Repeat tasks
# Why: Iterate over servers, pods, files, etc.
# How:
servers = ["web-01", "web-02", "db-01"]
for s in servers:
print("Checking server:", s)
# 🔹 Conditionals
# What: Run logic based on conditions
# Why: Alerts, decisions in automation
# How:
cpu_usage = 85
if cpu_usage > 80:
print("⚠️ High CPU usage!")
elif cpu_usage > 50:
print("Normal load")
else:
print("Idle")
# 🔹 Functions
# What: Reusable blocks of logic
# Why: Keep scripts modular and clean
# How:
def check_disk(disk_percent):
if disk_percent > 90:
return "Alert: Low disk space!"
return "Disk usage OK."
print(check_disk(75))
# 🔹 Comments & Docstrings
# What: Notes in code
# Why: Explain automation for teammates
# How:
def restart_service(service):
"""
Restart a given service on a Linux system.
service: str → service name (nginx, mysql, etc.)
"""
print(f"Restarting {service}...")
# (real code would use subprocess here)
restart_service("nginx")
"""
=======================================================
DATA STRUCTURES
=======================================================
"""
# 🔹 Lists
# What: Ordered collection
# Why: Store IPs, servers, logs
# How:
ips = ["10.0.0.1", "10.0.0.2"]
ips.append("10.0.0.3")
print("All IPs:", ips)
# 🔹 Tuples
# What: Immutable collection
# Why: Useful for constants like version numbers
# How:
version = (1, 24, 3) # k8s version
print("Cluster version:", ".".join(map(str, version)))
# 🔹 Dictionaries
# What: Key-value mapping
# Why: Store configs, JSON responses
# How:
server = {"name": "web-01", "ip": "10.0.0.1", "status": "active"}
print("Server name:", server.get("name"))
for k, v in server.items():
print(k, "=>", v)
# 🔹 Sets
# What: Unique collection
# Why: Deduplicate IPs or hosts
# How:
hosts = {"web-01", "db-01", "web-01"}
print("Unique hosts:", hosts)
"""
=======================================================
FILE & SYSTEM HANDLING
=======================================================
"""
import os
import subprocess
from pathlib import Path
# 🔹 File I/O
with open("servers.txt", "w") as f:
f.write("web-01\nweb-02\n")
with open("servers.txt", "r") as f:
print("Servers from file:", f.readlines())
# 🔹 OS Module
print("Home dir:", os.environ.get("HOME"))
print("Join path:", os.path.join("/etc", "nginx", "nginx.conf"))
# 🔹 Subprocess
result = subprocess.run(["echo", "Hello DevOps"], capture_output=True, text=True)
print("Command output:", result.stdout)
# 🔹 Pathlib
config_path = Path("/etc") / "nginx" / "nginx.conf"
print("Pathlib path:", config_path)
"""
=======================================================
ERROR HANDLING
=======================================================
"""
# 🔹 Try / Except
try:
x = 10 / 0
except ZeroDivisionError as e:
print("Error:", e)
finally:
print("Cleanup if needed")
# 🔹 Custom Exception
class ServerDownError(Exception):
pass
def check_server(status):
if not status:
raise ServerDownError("Server is DOWN!")
return "Server OK"
print(check_server(True))
"""
=======================================================
USEFUL BUILT-INS & ITERATION
=======================================================
"""
nums = [10, 20, 30]
# 🔹 Enumerate
for i, val in enumerate(nums):
print(f"Index {i} has value {val}")
# 🔹 Zip
names = ["web", "db"]
ips = ["10.0.0.1", "10.0.0.2"]
for n, ip in zip(names, ips):
print(n, "=>", ip)
# 🔹 Comprehension
active_servers = [s for s in servers if "web" in s]
print("Filtered servers:", active_servers)
"""
=======================================================
WORKING WITH DATA
=======================================================
"""
import json
import csv
import re
from datetime import datetime
# 🔹 JSON
data = {"name": "web-01", "ip": "10.0.0.1"}
with open("server.json", "w") as f:
json.dump(data, f)
print("JSON dump:", json.dumps(data))
# 🔹 YAML
# pip install pyyaml
import yaml
with open("server.yaml", "w") as f:
yaml.dump(data, f)
# 🔹 CSV
with open("report.csv", "w", newline="") as f:
writer = csv.writer(f)
writer.writerow(["name", "ip"])
writer.writerow(["web-01", "10.0.0.1"])
# 🔹 Datetime
now = datetime.now()
print("Current time:", now.strftime("%Y-%m-%d %H:%M:%S"))
# 🔹 Regex
log = "Error: Disk full on /dev/sda1"
match = re.search(r"Disk full on (.+)", log)
if match:
print("Disk issue on:", match.group(1))
"""
=======================================================
NETWORKING & APIS
=======================================================
"""
import requests
# 🔹 Requests
response = requests.get("https://api.github.com")
print("GitHub API status:", response.status_code)
"""
=======================================================
DEVOPS / SRE SPECIFIC
=======================================================
"""
import logging
# 🔹 Logging
logging.basicConfig(level=logging.INFO)
logging.info("Service started successfully.")
# 🔹 Argparse
import argparse
parser = argparse.ArgumentParser()
parser.add_argument("--service", help="Service to restart")
args = parser.parse_args([])
print("Service arg:", args.service)
# (Boto3, Kubernetes, Paramiko, Jinja2 would need their libraries and setup)
# Example with Jinja2 template:
from jinja2 import Template
tmpl = Template("server {{ name }} with IP {{ ip }}")
print(tmpl.render(name="web-01", ip="10.0.0.1"))
"""
=======================================================
TESTING & VALIDATION
=======================================================
"""
# 🔹 Assert
cpu = 70
assert cpu < 90, "CPU usage too high!"
# 🔹 Unittest
import unittest
class TestServer(unittest.TestCase):
def test_check_disk(self):
self.assertEqual(check_disk(70), "Disk usage OK.")
unittest.main(exit=False)
Last updated