Python was designed and developed by Guido van Rossum in the year 1989, and the first version was released in the year 1991.
- Python is a versatile programming language commonly used for application development across web, desktop, and mobile platforms. Although Python itself does not directly create physical infrastructure such as servers, networks, or cloud machines, it plays a crucial role in DevOps and cloud computing. Through libraries and tools like Ansible, SaltStack, boto3 (AWS), and Google Cloud SDK, Python enables engineers to automate, configure, and manage infrastructure efficiently using code
1. Introduction to Python
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Python is a General-purpose, High-level, Case-sensitive, and Easy-to-Learn programming language.
It is known for its Simple and Readability, making it highly Beginner-friendly.a) General-Purpose Language
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Python is a general-purpose programming language, meaning it is designed to be used for a wide variety of tasks, not restricted to a single domain.
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You can use Python for:
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🤖 AI and Data Automation — using pandas, numpy, openai, etc.
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📊 Data Analysis and Visualization — with matplotlib, seaborn, pandas
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🧩 Machine Learning & Deep Learning — with scikit-learn, tensorflow, pytorch
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☁️ Cloud and DevOps Automation — using boto3, azure, gcloud SDKs
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⚙️ Scripting & Process Automation — repetitive or scheduled tasks
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🖥️ OS and Network Automation — via os, subprocess, paramiko
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📑 Document Automation — Excel, Word, and PDF using openpyxl, python-docx, PyPDF2
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📁 File and Folder Operations — rename, move, delete, or backup files
b) High-level:
- Python is considered a high-level language because it is abstracted from the machine's hardware.(Python does not require you to deal with computer hardware directly (like CPU instructions or memory).)
- This makes Python easier to read, write, and understand, compared to low-level languages (like Assembly or C), which are closer to machine code.
- In other words, Python lets you focus more on solving problems rather than managing memory or other low-level tasks.
c) Case-Sensitive:
- Python treats uppercase and lowercase characters as different.
- For example, Variable and variable would be considered two different identifiers.
- This is important to remember when writing Python code, as the language will not automatically correct case mismatches.
d) Easy to Learn:
- Python has a simple and easy learn and easy-to-understand syntax, making it a great choice for beginners.
- meaning it’s a straight forward language
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2. Python is completely cross-platform or platform-independent
- Python is cross-platform, meaning you can write Python code on one operating system (e.g., Windows) and run it on another (e.g., macOS or Linux) without modifications, as long as Python is installed on that system.
3. Python is completely free and open-source
4. Python is an Interpreted language.
a) Interpreter-based languages(e.g., Python):
- The code is executed line by line, with each line being translated into machine code and executed on the fly.
- In this languages, all the debugging occurs at run-time.which makes debugging easier.
b) Compiler-based languages(e.g., C, C++, Java):
- The source code is compiled into machine code (binary) before execution.
- In this language, compilation errors prevent the code from compiling.
5. Python is a dynamically typed language, not a statically typed language
a) Statically typed languages (e.g., C, Java) require the programmer to specify the data type of variables at the time of
c or c++:
int a = 100
The data type (int) must be declared explicitly
int main() {
printf("hello, python");
return 0;
}
b) Dynamically typed languages (e.g., Python) allow the data type to be inferred based on the assigned value. You don't need to declare the type explicitly, making the code simpler and more flexible
- dynamically: no need to spcify any data type at the time of decleration
print("hello, python", "very, simple")
# you’re passing two separate arguments
print("hello, python", "very, simple", sep=" | ")
# By default, arguments are joined with a space ().
# variable name = value
var = 100 # Here, 'var' is dynamically typed as an integer.
print(var)
print(type(var))
- Expressive & Readable → Concise syntax, beginner-friendly, easy to learn.
- Free & Open Source → Available under the Python Software Foundation License.
- Cross-Platform & Portable → Runs on Windows, Linux, macOS without modification.
- Object-Oriented & Extensible → Supports OOP concepts and integration with C/C++.
- Rich Standard Library → Built-in modules for file I/O, web, data, and more.
- GUI Support → Frameworks like Tkinter, PyQt, and Kivy for desktop apps.
Interactive Mode
- You can run Python code interactively in the Python shell (REPL(Read-Eval-Print Loop)).
Script Mode
- You can write Python code in a file (e.g., test.py) and execute it via the command prompt:
Using Python IDLE
- Python's Integrated Development and Learning Environment (IDLE(Integrated Development and Learning Environment)) is a simple environment to write and run Python code.
Using PyCharm Editor
- PyCharm is a popular Python IDE for professional developers.
- You can download PyCharm Community Edition here.
- download PyCharm Community Edition : https://www.jetbrains.com/pycharm/download/?section=windows
Install Python extension VS Code
- Open VS Code → go to Extensions (left sidebar).
- Search for Python and install the official extension
- Desktop Apps (CUI/GUI) → Command-line or graphical applications.
- Web Development → Django, Flask.
- Networking & Cloud → Protocols, AWS (Boto3), Azure, GCP automation.
- Data Science & Analysis → Pandas, NumPy, Matplotlib.
- Business Apps → ERP, CRM systems.
- DevOps & Automation → Scripts for monitoring, server management.
- Scientific Computing → SciPy, SymPy (MATLAB-like).
- AI/ML → TensorFlow, Keras, PyTorch.
- Testing → unittest, pytest, Selenium.
- File Extension → Python files use
.py(e.g.,test.py). - Indexing
- Indexing means accessing individual elements from a sequence (like string, list, tuple) using their position number (index).
- Indexing starts from 0 (zero-based indexing).
- Negative indexing starts from the end (-1 is last element).
- Works with strings, lists, tuples, etc.
- Indexing gives only one element at a time.
s = "python"
print(s[0]) # Output: p
print(s[5]) # Output: n
print(s[-1]) # Output: n
print(s[-2]) # Output: o
- Slicing
- Slicing is used to extract a part (subsequence) from a sequence like a string, list, or tuple.
- start → index where slice begins (inclusive)
- stop → index where slice ends (exclusive)
- step → optional, defines jump or direction (default = 1)
s = "python"
print(s[0:4]) # Output: pyth
print(s[2:]) # Output: thon
print(s[:3]) # Output: pyt
print(s[::2]) # Output: pto
print(s[::-1]) # Output: nohtyp (reverse string)
- A. Comments
- Python are identified with a hash symbol(#), and extend to the end of the line#
- short cut key is ctrl + /
- using # for comments is a great practice in Python to describe what your code does.
- You can also use multi-line comments with triple quotes(""" """ ) for longer explanation
- B. Keywords or Reserved Words
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There are fewer restrictions on their usage. For example, you will get a “SyntaxError” if you try assigning a keyword to a variable
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Python keywords are special reserved words that have specific meanings and purposes and can’t be used for anything but those specific purposes.
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These keywords are always available—you’ll never have to import them into your code.
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Python keywords are different from Python’s built-in functions and types.
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list of python keyword module
import keyword
print(keyword.kwlist)
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Output = ['False', 'None', 'True', 'and', 'as', 'assert', 'async', 'await', 'break', 'class', 'continue', 'def', 'del', 'elif', 'else', 'except', 'finally', 'for', 'from', 'global', 'if', 'import', 'in', 'is', 'lambda', 'nonlocal', 'not', 'or', 'pass', 'raise', 'return', 'try', 'while', 'with', 'yield']
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'if' is keyword, we can not use as variable
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print(len(keyword.kwlist))
- Output 35
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Statically Typed vs Dynamically Typed:
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In some languages (like Java, C, C++), variables are statically typed, meaning you must declare the data type before using it.
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In Python, variables are dynamically typed — you don’t need to declare the type explicitly. Python infers the type automatically at runtime.
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Variables as Containers:
- Variables act like containers that store values. You can reuse and manipulate these values throughout the program.
- Variables as Identifiers:
- A variable is also called an identifier because it uniquely identifies the value or object stored in memory.
- Identifiers
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Any name is called identifiers (variable name or function name or any other name)
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Python Identifier is the name we give to identify a variable, function, class, module or other object.
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That means whenever we want to give an entity a name, that's called identifier.
- a) lowercase or uppercase.
- b) case-sensitive.
- c) allow digits(0-9).
- d) should not start with digit. wrong : 9acmarpu9 crroct : acmarpu9.
- e) should not be two parts (if two parts use _) (emp id) (emp_id).
- f) allow underscore (_).
- g) if any identifier starts with underscore(_) then it is private.
- h) no keywords or reserved words can be used as identifier.
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Python uses indentation (whitespace before a statement) to define the structure of the code — for example, in loops, conditionals, functions, and classes.
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Unlike many other languages such as C, C++, or Java, which use curly braces {} to group statements, Python relies only on indentation. Indentation Rules:
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4 spaces → According to PEP 8 (Python Enhancement Proposal 8), the recommended style is 4 spaces per indentation level.
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Consistency → You may technically use other spacing (e.g., 2 spaces), but mixing spaces and tabs or using inconsistent indentation will cause errors.
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Tabs vs Spaces → Spaces are preferred. While tabs can be used, Python 3 raises a TabError if you mix tabs and spaces in the same block.
#In Java
i = 10
if (i=10)
{
s.o.p("true"); # System.out.print
}
else
{
s.o.p("false");
}
#In Python
i = 10
if i ==10:
print("true") # *indent by four spaces = 1 level*
else:
print("false") # *indent by four spaces = 1 level*
- Definition:
- Structured programming is a logical, step-by-step programming style that emphasizes sequence, selection, and iteration.
✅ Key Idea:
- Divide a program into smaller logical blocks (functions) that control the flow of execution using loops and conditionals.
- It improves readability and reduces the use of goto.
- Definition: In function-oriented programming, the program is divided into functions, and data is passed between functions.
✅ Key Idea:
- Functions are the main building blocks.
- Focuses on actions (functions) that operate on data.
- Data and functions are separate.
- Definition:
- OOP organizes code around objects, which combine data (attributes) and functions (methods) into a single unit. ✅ Key Idea:
- Everything is treated as an object.
- Objects represent real-world entities.
- Focus on what to model rather than how to do it.