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Readme.md

Python Learning Notes

Day 1 - Basics

1. Taking User Input and Printing Output

print("Hello, " + input("What is your name? ") + "!")

Explanation:

  • input() takes input from the user.
  • print() displays output.
  • + is used for string concatenation.

Example Output:

What is your name? Mathew
Hello, Mathew!

2. Store Input in a Variable

name = input("What's your name? ")
print(name)

Explanation:

  • Variables are used to store values.
  • Here, the variable name stores the user's input.

3. Find Length of User Input

print(len(input("Tell me your name: ")))

Explanation:

  • len() returns the number of characters.
  • The input is passed directly into len().

4. Using Variables with len()

username = input("What is your name? ")
length = len(username)

print("Your name has " + str(length) + " characters")

Explanation:

  • len() returns an integer.
  • Integers must be converted to strings using str() before concatenation.

5. Variable Swapping Exercise

Question: We have two variables:

glass1 = "milk"
glass2 = "juice"

Swap the contents without typing "milk" or "juice".

Solution:

temp = glass1
glass1 = glass2
glass2 = temp

Result:

glass1 = juice
glass2 = milk

6. Band Name Generator Project

username = input("What is your name? ")
petname = input("What is your pet name? ")

print("Hello, " + username + "!")
print("Your band name is " + username + " " + petname)

Example Output:

What is your name? Mathew
What is your pet name? Bruno

Hello, Mathew!
Your band name is Mathew Bruno

Day 2 - Data Types

1. Python Data Types

String (str)

name = "Mathew"

Stores text data.

Integer (int)

age = 25

Stores whole numbers.

Float (float)

salary = 25000.50

Stores decimal numbers.

Boolean (bool)

is_active = True

Stores either True or False.

2. String Indexing (Subscripting)

print("Hello"[0])

Output:

H

Explanation:

  • Strings are sequences of characters.
  • Index starts from 0.
Character H e l l o
Index 0 1 2 3 4

Examples:

print("Hello"[1])  # e
print("Hello"[4])  # o

3. Checking Data Types

print(type(1234))
print(type(12.34))
print(type("Hello, World!"))
print(type([1, 2, 3, 4, 5]))
print(type((1, 2, 3, 4, 5)))
print(type({1, 2, 3, 4, 5}))
print(type({"a": 1, "b": 2, "c": 3}))
print(type(True))
print(type(None))
print(type(1 + 2j))
print(type(len))

Output:

<class 'int'>
<class 'float'>
<class 'str'>
<class 'list'>
<class 'tuple'>
<class 'set'>
<class 'dict'>
<class 'bool'>
<class 'NoneType'>
<class 'complex'>
<class 'builtin_function_or_method'>

4. Type Conversion (Type Casting)

Convert Integer to String

length = 10

print("Length is " + str(length))

Convert String to Integer

num = "100"

print(int(num) + 50)

Output:

150

Example Program

user = input("Enter your name: ")

print(f"Hello, {user}!")

length = len(user)

print(f"Your name has {length} characters.")

print("Number converted to string: " + str(length))

print("Goodbye!")

Example Output:

Enter your name: Mathew

Hello, Mathew!
Your name has 6 characters.
Number converted to string: 6
Goodbye!

5. Implicit Type Casting

Python automatically converts some data types when needed.

num1 = 10
num2 = 5.5

result = num1 + num2

print(result)
print(type(result))

Output:

15.5
<class 'float'>

Explanation:

  • Integer (10) is automatically converted to float (10.0).
  • Result becomes a float.

Key Concepts Learned So Far

✅ print() ✅ input() ✅ Variables ✅ len() function ✅ String concatenation ✅ f-Strings ✅ Data Types (str, int, float, bool) ✅ String indexing ✅ type() function ✅ Type Casting (str(), int(), float()) ✅ Implicit Type Conversion ✅ Variable Swapping ✅ Mini Project - Band Name Generator

Python Learning Notes

Day 2 (Continued) - Operators and Conditional Statements

1. Tip Calculator Project

Program

a = float(input("What's the bill amount? "))
b = float(input("What's the tip percentage? "))
c = int(input("How many people are splitting the bill? "))

tip = a * (b / 100)
total = a + tip
per_person = total / c

print(f"Each person should pay: ${per_person:.2f}")

Concepts Used

float()

Converts input into a decimal number.

price = float("150.75")

int()

Converts input into a whole number.

people = int("5")

Arithmetic Operators

Operator Meaning Example
+ Addition 10 + 5
- Subtraction 10 - 5
* Multiplication 10 * 5
/ Division 10 / 5
// Floor Division 10 // 3
% Modulus 10 % 3
** Power 2 ** 3

f-Strings

name = "Mathew"
print(f"Hello {name}")

Formatting Decimal Places

price = 25.6789
print(f"{price:.2f}")

Output:

25.68

Conditional Statements

Conditional statements allow a program to make decisions.

Basic Syntax

if condition:
    # code
else:
    # code

Example

print("Welcome to the roller coaster!")

height = int(input("What is your height in cm? "))

if height >= 120:
    print("You can ride the roller coaster!")
else:
    print("Sorry, you have to grow taller before you can ride.")

Flow

Condition True  -> Execute IF block
Condition False -> Execute ELSE block

Comparison Operators

Comparison operators compare two values and return either True or False.

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

Examples

print(10 > 5)

Output:

True

print(10 == 5)

Output:

False

Important

=

Assignment operator

==

Comparison operator

Example:

age = 25

Assigns 25 to age.

age == 25

Checks if age equals 25.

Modulus Operator (%)

The modulus operator returns the remainder after division.

10 % 2

Output:

0

10 % 3

Output:

1

Even or Odd Number Program

a = int(input("Enter a number: "))

if a % 2 == 0:
    print("The number is even")
else:
    print("The number is odd")

Logic

Number % 2 = 0  -> Even
Number % 2 = 1  -> Odd

Nested If Statements

An if statement inside another if statement.

Example

height = int(input("What is your height in cm? "))
age = int(input("What is your age? "))

if height >= 120:
    print("You can ride the rollercoaster!")

    if age <= 18:
        print("Please pay $7.")
    else:
        print("Please pay $12.")
else:
    print("Sorry, you have to grow taller before you can ride.")

Flow

Height Check
    |
    ├── False → Not allowed
    |
    └── True
            |
            Age Check
                |
                ├── <=18 → $7
                └── >18  → $12

Multiple Conditions (if - elif - else)

Used when there are multiple possible outcomes.

Syntax

if condition1:
    code
elif condition2:
    code
elif condition3:
    code
else:
    code

Example

marks = 85

if marks >= 90:
    print("Grade A")
elif marks >= 80:
    print("Grade B")
elif marks >= 70:
    print("Grade C")
else:
    print("Fail")

Output:

Grade B

BMI Calculator Project

BMI (Body Mass Index) measures body weight relative to height.

Formula

BMI = \frac{weight}{height^2}

Program

weight = int(input("Enter your weight in kg: "))
height = float(input("Enter your height in meters: "))

bmi = weight / (height ** 2)

if bmi < 18.5:
    print("Underweight")
elif bmi < 25:
    print("Normal weight")
elif bmi < 30:
    print("Overweight")
else:
    print("Obese")

BMI Categories

BMI Range Category
Below 18.5 Underweight
18.5 - 24.9 Normal
25 - 29.9 Overweight
30 and above Obese

Concepts Used

Exponent Operator (**)

2 ** 3

Output:

8

Used in BMI calculation:

height ** 2

means:

height × height

Logical Operators (Important Missing Concept)

Used to combine multiple conditions.

Operator Meaning
and Both conditions must be True
or At least one condition must be True
not Reverses the result

AND

age = 20
height = 170

if age >= 18 and height >= 150:
    print("Allowed")

OR

if age >= 18 or height >= 150:
    print("Allowed")

NOT

is_banned = False

if not is_banned:
    print("Access Granted")

Key Concepts Learned So Far

✅ print()

✅ input()

✅ Variables

✅ len()

✅ Strings

✅ Integers

✅ Floats

✅ Booleans

✅ String Indexing

✅ type()

✅ Type Casting

✅ Arithmetic Operators

✅ Comparison Operators

✅ Modulus Operator

✅ Exponent Operator

✅ Conditional Statements

✅ if

✅ else

✅ elif

✅ Nested if

✅ Logical Operators (and, or, not)

✅ f-Strings

✅ Tip Calculator Project

✅ BMI Calculator Project

✅ Even/Odd Checker Project

✅ Roller Coaster Project