Welcome! This channel is for anyone starting out with Python.
I'm learning too — just sharing what I know and picking up more along the way.
We'll cover the basics step by step, help each other, and have some fun doing it.
One day, we'll grow this into a full community of coders.
No stress. Just learning, curiosity, and progress.

❓ Questions & Help

If you have any questions about the lessons, PDFs, or Python in general, feel free to ask in this group (https://t.me/python_programming0).

Don't stay stuck — ask and learn 💡🐍

Introduction to Programming with Python

---

What is Python?

Python is a popular programming language created by Guido van Rossum in 1991.

It is known for:
- Simplicity
- Readability
- Flexibility
- Powerful libraries

Python is beginner-friendly while still being powerful enough for AI, web development, and automation.

---

What is Python Used For?

- Web Development
- Software Development
- Data Science & Mathematics
- Automation & System Scripting

Python works on multiple platforms:
- Windows
- Linux
- Mac
- Raspberry Pi

---

Important Concept: Indentation

Unlike many programming languages that use { }, Python uses indentation (spaces) to define code blocks.

Example:

if 5 > 2:
    print("Five is greater than two")

Proper indentation is required in Python.

---

Your First Python Program

print("Hello World")

This prints text to the screen.

---

Reading User Input

Use the input() function to get data from users.

name = input("Please enter your name: ")

print(f"Hi {name}, nice to meet you!")

---

Variables in Python

Variables are containers used to store data.

x = 5
y = "John"

Python automatically detects the data type.

---

Casting

Casting is used to force a variable into a specific data type.

str(3)      # '3'
int(3.8)    # 3
float(3)    # 3.0

---

Variable Naming Rules

- Must start with a letter or underscore _
- Cannot start with a number
- Can contain letters, numbers, and underscores
- Case-sensitive (age, Age, and AGE are different)
- Cannot use Python keywords like:
- if
- while
- print

---

Naming Conventions

Camel Case:

myVariableName

Pascal Case:

MyVariableName

Snake Case (Recommended in Python):

my_variable_name

---

Built-in Data Types

Python includes several built-in data types:

- Text → str
- Numeric → int, float, complex
- Sequence → list, tuple, range
- Mapping → dict
- Boolean → bool

Check a variable type using type():

print(type(5))

Output:

<class 'int'>

---

Comments in Python

Comments make code easier to understand.

Single-line comment:

# This is a comment

Multi-line comment:

"""
This is a multi-line comment
"""

Control Structures and Loops in Python

---

Conditional Statements

Conditional statements allow programs to make decisions based on conditions.

They help control the flow of a program by executing different code depending on whether a condition is True or False.

---

Comparison Operators

| Operator | Meaning |
|----------|----------|
| == | Equal to |
| != | Not equal to |
| < | Less than |
| <= | Less than or equal to |
| > | Greater than |
| >= | Greater than or equal to |

---

If, Elif, and Else

- if → checks the first condition
- elif → checks another condition if previous ones are False
- else → runs if none of the conditions are True

Example:

a = 200
b = 33

if b > a:
    print("b is greater than a")

elif a == b:
    print("a and b are equal")

else:
    print("a is greater than b")

---

Logical Operators

Logical operators combine multiple conditions.

---

AND Operator

Returns True only if both conditions are True.

a = 200
b = 33
c = 500

if a > b and c > a:
    print("Both conditions are satisfied")

---

OR Operator

Returns True if at least one condition is True.

if a > b or a > c:
    print("At least one condition is True")

---

NOT Operator

Reverses the result.

a = 33
b = 200

if not a > b:
    print("a is NOT greater than b")

---

Loops in Python

Loops repeat code multiple times while a condition is met.

Python mainly uses:
- while loop
- for loop

---

The While Loop

Executes repeatedly while the condition remains True.

i = 1

while i < 6:
    print(i)
    i += 1

Important:
Always update the loop variable to avoid infinite loops.

---

Break Statement

Stops the loop immediately.

i = 1

while i < 6:
    print(i)

    if i == 3:
        break

    i += 1

---

Continue Statement

Skips the current iteration and continues with the next one.

i = 0

while i < 6:
    i += 1

    if i == 3:
        continue

    print(i)

---

Else with Loops

The else block runs once when the loop condition becomes False.

i = 1

while i < 6:
    print(i)
    i += 1

else:
    print("Loop finished")

---

The For Loop

A for loop is used to iterate through sequences such as:
- Lists
- Tuples
- Strings

Example:

fruits = ["apple", "banana", "cherry"]

for x in fruits:
    print(x)

---

Practice Exercises

1. Write a program to check whether a number is positive, negative, or zero.

2. Print all even numbers from 1 to 20 using a loop.

3. Create a loop that stops when the number 5 is reached.

4. Loop through a string and print each character separately.

Functions and Recursion in Python

---

Working with Functions

A function is a reusable block of code that runs only when it is called.

Functions help:
- Organize code
- Avoid repetition
- Make programs easier to manage

---

Default Parameter Values

A function can use a default value if no argument is provided.

def my_function(country="Norway"):
    print("I am from " + country)

my_function("Sweden")
my_function()

Output:

I am from Sweden
I am from Norway

---

Passing Sequences as Arguments

Functions can receive lists, tuples, dictionaries, and other data types.

def my_list_function(food):
    for x in food:
        print(x)

fruits = ["apple", "banana", "cherry"]

my_list_function(fruits)

---

Return Values

Use the return statement to send data back from a function.

def multiply_by_five(x):
    return 5 * x

result = multiply_by_five(3)

print(result)

Output:

15

---

Recursion

Recursion is when a function calls itself.

It is useful for:
- Mathematical problems
- Repeated calculations
- Breaking problems into smaller parts

---

Important Note

Recursive functions must have a stopping condition (base case).

Without it, the function may run forever and crash the program.

---

Recursion Example

def tri_recursion(k):

    if k > 0:
        result = k + tri_recursion(k - 1)
        return result

    else:
        return 0

print(tri_recursion(6))

This function adds numbers from 6 down to 0.

---

Lambda Functions

A lambda function is a small anonymous function.

Syntax:

lambda arguments : expression

Example:

x = lambda a, b: a * b

print(x(5, 6))

Output:

30

---

Why Use Lambda Functions?

Useful for:
- Short operations
- One-line functions
- Functional programming techniques

---

Practice Exercises

1. Create a Fibonacci sequence program.

The sequence starts with:
0, 1, 1, 2, 3, 5, 8...

Each number equals the sum of the previous two numbers.

---

2. Write a function that accepts a positive integer and calculates the sum of all numbers down to 0.

Example:

Input: 5
Output: 15

Data Structures: Lists in Python

---

Introduction to Lists

Lists are used to store multiple items in a single variable.

They are one of the main built-in collection data types in Python.

---

Key Characteristics of Lists

- Ordered → Items keep their position
- Changeable → Items can be modified
- Allow Duplicates → Same value can appear multiple times

---

Creating a List

thislist = ["apple", "banana", "cherry"]

print(thislist)

---

Accessing List Items

Lists use indexes.

thislist = ["apple", "banana", "cherry"]

print(thislist[0])
print(thislist[1])

Output:

apple
banana

---

List Indexing

"apple"   "banana"   "cherry"
   0          1           2
  -3         -2          -1

- Positive indexes start from the beginning
- Negative indexes start from the end

---

Negative Indexing

thislist = ["apple", "banana", "cherry"]

print(thislist[-1])

Output:

cherry

---

Range of Indexes

The start index is included, but the end index is excluded.

thislist = ["apple", "banana", "cherry", "orange", "kiwi"]

print(thislist[2:4])

Output:

['cherry', 'orange']

---

Changing List Items

Use the index number to modify an item.

thislist = ["apple", "banana", "cherry"]

thislist[1] = "blackcurrant"

print(thislist)

---

List Length

Use len() to count items.

print(len(thislist))

---

Essential List Methods

---

append()

Adds an item to the end.

fruits = ["apple", "banana"]

fruits.append("orange")

print(fruits)

---

insert()

Adds an item at a specific position.

fruits.insert(1, "cherry")

print(fruits)

---

remove()

Removes a specific item.

fruits.remove("banana")

print(fruits)

---

pop()

Removes the last item.

fruits.pop()

print(fruits)

---

Membership Test

Use in to check if an item exists.

if "apple" in fruits:
    print("Yes, it is in the list!")

---

Practice Exercises

1. Create a list of 5 favorite movies and print the third item.

2. Replace the second item in a list with a new value.

3. Add two new items to a list using:
- append()
- insert()

4. Check if "banana" exists in a list.