Introduction to Python

1.1 What is Python?

Python is a programming language. You can use it to write small scripts, automation tools, web applications, and many other types of software.

Python is popular because its code is easy to read and quick to write.

print("Hello, Python!")

When you run this program, Python displays:

Hello, Python!

A Python program is usually saved in a file ending with .py. You can run the file with the Python interpreter:

python3 hello.py

1.2 A Short History

Python was created by Guido van Rossum. The first public version was released in 1991.

The language was designed with a simple goal: developers should be able to write clear and useful programs without unnecessary complexity.

Python 3 is the current version. Python 2 reached the end of its life on January 1, 2020, so new projects should use Python 3.

# Python 3
print("Use Python 3 for new projects")

1.3 Main Features of Python

1. Easy to read syntax
2. Cross platform
3. Large standard library
4. Many third-party packages
5. Dynamically typed

1. Easy-to-Read Syntax

Python code often looks close to plain English. It uses indentation to show which lines belong together.

name = "Alex"

if name:
    print(f"Hello, {name}")

2. Cross-Platform

Python is available on Linux, Windows, and macOS. The same script can often run on all three operating systems.

3. Large Standard Library

Python includes useful modules for files, JSON, dates, networking, and many other common tasks. You can use these modules without installing extra packages.

import json

server = {"name": "web-01", "status": "running"}
print(json.dumps(server))

4. Many Third-Party Packages

When the standard library is not enough, you can install packages from PyPI. Examples include:

• boto3 for AWS
• requests for HTTP APIs
• pytest for testing
• pandas for data analysis

5. Dynamically Typed

You do not have to declare a variable type before using it. Python works out the type from the value.

count = 5
name = "web-server"

print(type(count))
print(type(name))

1.4 Why Learn Python?

Python is useful because it helps you solve real problems with a small amount of code.

• Automation: Automate repetitive tasks such as moving files, creating reports, and checking servers.
• DevOps: Write scripts for CI/CD, monitoring, deployments, and infrastructure management.
• Cloud: Use cloud SDKs such as boto3 to manage AWS resources.
• Web development: Build websites and APIs with frameworks such as Django, Flask, and FastAPI.
• Data and AI: Work with data and machine learning using libraries such as pandas, NumPy, and PyTorch.

1.5 Where Is Python Used?

Python is commonly used for:

1. Web development: Building websites and APIs.
2. Automation: Replacing repetitive manual work with scripts.
3. Data science: Cleaning, analyzing, and visualizing data.
4. Machine learning: Building and using machine-learning models.
5. Networking: Creating API clients, monitoring tools, and network scripts.
6. Cybersecurity: Analyzing logs and automating security checks.

1.6 Why Python Is Useful for DevOps

DevOps engineers work with servers, cloud services, APIs, containers, and CI/CD pipelines. Python can connect these systems and automate work between them.

Infrastructure Automation

Python can connect to servers and run administrative tasks. Libraries such as paramiko can be used for SSH automation.

import paramiko

client = paramiko.SSHClient()
client.set_missing_host_key_policy(paramiko.AutoAddPolicy())
client.connect('server01', username='deploy', key_filename='id_rsa')
stdin, stdout, stderr = client.exec_command('uptime')
print(stdout.read().decode())

AWS Automation

boto3 is the AWS SDK for Python. It allows Python programs to work with AWS services such as EC2, S3, Lambda, and IAM.

import boto3

ec2 = boto3.client('ec2')
response = ec2.describe_instances()
# The response contains information about EC2 instances.

CI/CD

Python scripts can run tests, build packages, check deployments, and trigger other tools inside Jenkins, GitHub Actions, or GitLab CI.

Monitoring

Python can check application health, read metrics, process logs, and send alerts.

Configuration Management

Ansible is built with Python. Python knowledge is useful when creating custom Ansible modules or automation scripts.

1.7 Python Compared with Other Tools

Python and Bash

Bash is excellent for short commands and simple Linux tasks. Python is usually better when a script needs data structures, reusable functions, API calls, or detailed error handling.

Python and Go

Go is compiled and is a good choice for fast, standalone tools. Python is often quicker to write and is popular for internal automation.

Python and PowerShell

PowerShell is a strong choice for Windows and Microsoft administration. Python is a good choice when the same automation must run across Linux, Windows, and macOS.

When to Choose Each?

Quick Interview Answer

Python is a general-purpose programming language created by Guido van Rossum and first released in 1991. It is popular because its syntax is easy to read and it helps developers write useful programs quickly. Python is widely used for automation, DevOps, cloud engineering, web development, data science, and machine learning.

Key Takeaways

• Python is a readable, general-purpose programming language.
• Python 3 should be used for new projects.
• Python works on Linux, Windows, and macOS.
• Python is useful for automation, cloud, DevOps, web development, and data work.
• Python can be extended with packages from PyPI.

Common Mistakes

• Assuming Python is only used for data science or machine learning.
• Using Python 2 for a new project. Python 2 is no longer supported.
• Choosing Python for every task. Bash, Go, or PowerShell may be a better fit in some situations.

Chapter practice checkpoint

Run python --version (or python3 --version on systems using that command). Save print("Hello, automation!") in hello.py, then run it from the terminal with python hello.py.

Expected output: Hello, automation! on its own line.

Knowledge check: What is the difference between the interpreter prompt and a saved script?

You are ready to continue when you can locate your script, run it, change its message, and explain the output.