Python Notes

1. Python Introduction

Python is a high-level, interpreted, general-purpose language known for readability, versatility, and a massive ecosystem.

Clean syntax with indentation
Used in web, data science, AI, automation
Dynamically typed, open source

2. print() Function

print("Hello, World!")
name =
                                "Alice"
print(f"My name is {name}")

print() displays output
f-strings (Python 3.6+) for formatting
\n for newlines

3. Operators

Arithmetic
+, -, *, /, //, %, **

Comparison
==, !=, >, <, >=, <=

Logical
and, or, not

Identity
is, is not

Membership
in, not in

a, b = 10, 3
print(a // b) #
                                3
print(a ** b) # 1000

4. if-else Statements

age = 18
if age >= 18:

                                print("Adult")
else:
 print("Minor")

#
                                ternary
status = "Adult" if age >= 18 else
                                "Minor"

if-elif-else for multiple conditions
Nested if supported

5. Lists

Ordered, mutable collection [ ]

fruits = ["apple",
                                "banana"]
fruits.append("orange")
squares = [x**2
                                for x in range(5)]

Indexing, slicing, append(), pop()
List comprehension: [x**2 for x in range(10) if x%2==0]

6. Tuples

Ordered, immutable ( )

colors = ("red", "green",
                                "blue")
x, y = (10, 20) # unpacking

Faster than lists, can be dictionary keys
Return multiple values from functions

7. Sets

Unordered collection of unique elements { }

A = {1,2,3,4}
B =
                                {3,4,5,6}
print(A | B) # union
print(A & B) #
                                intersection

8. Dictionaries

Key-value pairs {key: value}

student = {"name": "John", "age":
                                20}
print(student.get("name"))
student["grade"] =
                                "A"

.keys(), .values(), .items()
Dictionary comprehension: {x: x**2 for x in range(5)}

9. Loops

# for loop
for i in range(5):

                                print(i)

# while
count = 0
while count <
                                3:
 count += 1

break, continue
enumerate() for index+value

10. Functions

def greet(name):
 return f"Hello,
                                {name}"

# lambda
square = lambda x: x**2

*args (tuple) and **kwargs (dict)
Default parameters, docstrings

11. File Handling

with open("file.txt", "w") as f:

                                f.write("Hello\n")

with open("file.txt", "r") as
                                f:
 content = f.read()

Modes: r, w, a, b
CSV handling via csv module

12. Core Concepts

Variable: named storage location
Data types: int, float, str, bool, list, tuple, set, dict
Scope: global vs local
Exception handling: try-except
Module: single .py file, Package: collection of modules

13. Student Management System

Complete example with class, file I/O, and menu.

import
                                os

class StudentManager:
 def
                                __init__(self):
 self.students = []

                                self.load_students()

 def add_student(self):

                                name = input("Name: ")
 age = int(input("Age: "))

                                grade = input("Grade: ")
 self.students.append({'id':
                                len(self.students)+1, 'name': name, 'age': age, 'grade':
                                grade})

 def view_students(self):
 for s in
                                self.students:
 print(f"{s['id']} {s['name']}
                                {s['age']} {s['grade']}")

 def
                                save_students(self):
 with open("students.txt", "w")
                                as f:
 for s in self.students:

                                f.write(f"{s['id']},{s['name']},{s['age']},{s['grade']}\n")


                                def load_students(self):
 if
                                os.path.exists("students.txt"):
 with
                                open("students.txt") as f:
 for line in f:
 data =
                                line.strip().split(",")
 if len(data)==4:

                                self.students.append({'id': int(data[0]), 'name':
                                data[1], 'age': int(data[2]), 'grade': data[3]})


                                def run(self):
 while True:
 # menu logic omitted
                                for brevity
 pass

Full code in notes includes menu, search, delete, and persistence.

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