# Python Concepts Notes.md

Python Concepts Notes (Simple Format)

VARIABLES

• Used to store data.
• No need to declare type.
• Syntax:

x = 10
name = "Shreyas"

DATA TYPES

• int → whole numbers
• float → decimals
• str → text
• bool → True/False
• list → ordered collection
• tuple → fixed collection
• dict → key-value pairs
• set → unique items

TYPE CASTING

• Convert one type to another.

int("5")
float(10)
str(20)

INPUT & OUTPUT

• Input always comes as string.

name = input("Enter name: ")
print(name)

OPERATORS

• Arithmetic: +, -, *, /, %, //, **
• Comparison: ==, !=, >, <, >=, <=
• Logical: and, or, not
• Assignment: =, +=, -=, *=, /=

IF CONDITIONS

• Used for decision-making.

if condition:
    # code
elif condition:
    # code
else:
    # code

LOOPS

FOR LOOP

• Used when you know how many times to repeat.

for i in range(5):
    print(i)

WHILE LOOP

• Runs until condition becomes false.

while condition:
    # code

BREAK & CONTINUE

• break → stop loop
• continue → skip iteration

LISTS

• Ordered, changeable.

arr = [1, 2, 3]
arr.append(4)
arr.remove(2)

TUPLES

• Ordered, unchangeable.

t = (10, 20, 30)

SETS

• Unordered, unique items.

s = {1, 2, 2, 3}

DICTIONARIES

• Key-value pairs.

student = {"name": "Shreyas", "age": 21}
print(student["name"])

FUNCTIONS

• Reusable blocks of code.

def add(a, b):
    return a + b

LAMBDA

• Small anonymous function.

square = lambda x: x*x

MODULES

• Reuse code from other files.

import math

FILE HANDLING

f = open("data.txt", "r")
data = f.read()
f.close()

EXCEPTION HANDLING

try:
    x = 10/0
except ZeroDivisionError:
    print("Cannot divide")

CLASSES & OBJECTS

class Car:
    def __init__(self, brand):
        self.brand = brand

c = Car("BMW")

INHERITANCE

class A:
    pass
class B(A):
    pass

OOP CONCEPTS

• Class
• Object
• Encapsulation
• Abstraction
• Inheritance
• Polymorphism

LIST COMPREHENSION

nums = [x for x in range(5)]

GENERATORS

def gen():
    yield 1
    yield 2

PACKAGES

pip install package_name